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PHYSICO-CHEMICAL STUDIES ON METAL CHELATES OF NITROGEN
AND SULPHUR CONTAINING LIGANDS
ABSTRACT
THESIS ^yeiS/IITTED FOR THE DEGREE OF V
Bottor of ^IitloiBiopIi? IN
CHEMISTRY
BY
SARTAJ TABASSUM
DEPARTMENT OF CHEMISTRY ALIGARH MUSLIM UNIVERSITY
ALIGARH (INDIA)
1 9 8 7
.t,j>!l^»ii.1ti?*.»i
ABSTRACT
Lanthanides which have incompletely filled 'f orbitals
present a very interesting chemistry in several aspects mainly
as a consequence of their ability to expand the octet offering
possibilities of increased coordination number around them.
An added point of recent interest in their chemistry is the
findings that they have toxic behaviour towards animal and man.
In aqueous solution the coordination sites are occupied by
water molecules and coordination only by very strong ligand is
possible.
In addition, cumulative harmful effects of lanthanides
are generally unknowh, but i-n th^ "light of the results obtained
from experiments on the effects of massively administered
quantities suitable- preventive precautions are undoubtedly
advisable. General effects of the dozes administered to
animals are hyperglycemia, decressed blood pressure and develop
ment of granulomas. Lanthanides act as anti blood coagulant.
They accumulate chiefly in lever and eliminated very slowly.
Sulphur and nitrogen containing ligands are known to
be toxic and their toxicity is enhanced after complexation
with metal ions. In view of this an attempt has been made to
characterize lanthanide complexes with such ligand and to study
relative toxicological behaviour of these ligands and their
complexes towards insects and fungi.
Chelates of barbituric-;(BA) 5,^-diethyl barbituric-,
(DBA) and thiobcrbituric acids(TBA) with La(III), Ce(lll),
Pr(TIl), Nd(IIl), Sm(lll), Eu(IIl), Gd(lII), Tb(III), Dy(III),
Ho(IIl), Er(lII), Yb(lII) and Lu(lII) have been synthesized in
1:3(M:L) ratio. They have been characterized on the basis of
elemental analyses, molecular weight determination, UV/visible-
and IR spectroscopy. The pH-metric study carried out at three
different temperatures viz., 25°, 30°, 35°C and 0.1 M ionic
strength indicated that there is only one dissociable proton
in these acids. These chelates have been found to be electro
lyte in dimethyl formamide. On the basis of formation
constants the metal ions have been arranged in the order;
La< Ce< Pr< Nd < Gd < Er < Sm<: Eu < Ho < Dy <:Tb< Yb (BA)
La < Ce < Gd <: Dy < Pr < Dy < Nd <i Sm < Ho < Er <: Eu < Yb <: Lu (DBA)
La< Ce <Gd <Tb< Pr< Nd< Sm< Dy< Ho<Eu<Er<.Yb <.Lu (TBA)
La(IIl), Ce(lll), Pr(IIl), Nd(IIl), Gd(IIl), Dy(lll),
Ho(lll) and Er(lII) complexes of Schiff bases derived from
sulphamethoxazole and salicylaldehyde(l) and -thiophene 2-
aldehyde(ll) have been characterized on the basis of IR-,
NMR-, UV-visible spectroscopy, elemental analyses, conductance
measurements and molecular weight determination.
The Schiff bases act as monobasic bidentate ligands. The
equilibrium constant has been studied in solution at 25, 30
ii
and 35°C. The nephelauxetjc effect {^-0 ) , ooric Ing
paraineter(/|), b* and Sinha covalency parameter, fi have been
calculated. The positive values indicated the covalent
nature of metal-ligand bond. The covalent nature of the
complexes has also been supported by molar conductance
measurement. The toxicity of the Schiff bases and their
complexes were evaluated against insects. The LDCQ value
of cockroaches and % growth inhibition of the fungi showed
that the toxicity is enhanced after complexation.
Synthesis of the Schiff bases derived from S-benzoyl
sulph enilamide dithiocarbaraate and thiophene 2-aldehyde and
4-N, N-dimethyl amino benzaldehyde has been carried out.
Their complexes of the type (ML)2C1 .aH^O where M=La(III),
Ce(lII), Pr(lll), Nd(IIl), Gd(IIl), DyCH'Il), Ho(lII),
Er(III) and Yb(III)^ have been characterized by IR-, NMR-,
UV/visible spectroscopy, elemental analyses magnetic moment
measurement. The nephelauxetic effect (1 -^), bonding
parameter, P , b* and Sinha covalency parameter^ S and
the molar conductance measurement in nitrobenzene reflect
covalent nature for the complexes. The equilibrium constant o
and thermodynamic data have been studied in solution at 25,
30, 35 C. LogK has been found to be inversely proportional
to temperature. The toxicity of the schiff bases and their
complexes were evaluated against insects and ftingi. The hD^^
for cockroaches and % inhibition in growth of the f\ingi showed
111
that complexes are more toxic than ochil'f bases.
Some new 0:N:S ana N:S donor ligand namely, S.
benzoyl N-(N,0-hydroxy benzaldehyde) dithiocarbazate (L^),
S. benzoyl N-(N, N-dimethyl amino benzaldehyde) dithio
carbazate (L2), S. benzoyl N- (N-thiophene 2-aldehyde)
dithiocarbazate (L,) and their complexes with La(III),
Ce(IIl), Pr(IIl), Nd(lll), Sm(IIl), Gd(lll), Tb(IIl), Dy(lll),
Ho(IIl), Er(IIl), Yb(lll) and Lu(lll) have been synthesized.
The characterization has been done by known physical methods.
The molar conductance measured in nitrobenzene suggest their
covalent nature and magnetic moment values exhibit paramag
netism. The values of log K and -AG have been calculated
pH-metrically. The log K values for the complexes with Schiff
bases foMow the order L^> Lp^ L,. Toxicity of the compounds
has been evaluated against cockroaches and fungi(Aspergillus
flavus and Aspergillus niger). The LDCQ and % inhibition
obstensibly demonstrate greater efficacy for the complexes
than for the free bases.
Reaction of Cyclopentanone-(I), 2,2-disubstituted
methyl propyl-(ll), 2,2-disubstituted hexyl methyl(lll)
thiazolidin-A-ones with lanthanide(IIl) ions yield complexes
of the composition M(L)^.2HpO.
The structural elucidation of the chelates is done
by elemental analysis, IR-, NKR- and electronic spectroscopy,
magnetic and conductance measurement. These studies are
indicative of their covalent nature. From solution studies
iv
'?
log K values appear to be inversely proportjonal to
temperature. In addition, the toxicity of the organic bases
and their corresponding complexes has also been investigated,
There is shear evidence that the metallation of the ligand
pronounces the toxicity which is also reflected irom
LDj-p. values. They also act as growth inhibitor in the case
of common fungi. On the basis of the mortality data the
thiazolidin-4-ones may be arran'ged in the ascending order
of their toxicity.
Ill - II < I
It has been noted that the compounds containing
methyl group cause an increase in fungicidal properties.
The fungitoxicity of the ligands follow the order;
III^N^II > I
which is exactly the reverse to those found for insects.
PHYSICO-CHEMICAL STUDIES ON METAL CHELATES OF NITROGEN
AND SULPHUR CONTAINING LIGANDS
THESJS SUBMITTED FOR THE DEGflEE OF
Bottor of $^ilosiDp]^p IN
CHEMISTRY
BY
SARTAJ TABASSUM
DEPARTMENT OF CHEMISTRY ALIGARH MUSLIM UNIVERSITY
ALIGARH (INDIA)
1 9 8 7
T3601
Ref. So.
DEPARTMENT OF CHEMISTRY
A L I G A R H M U S L I M U N I V E R S I T Y A L I G A R H U. P I N D I A
/)<-•
PHONE-OflBce : 5515
Certified that the work embodied in
this thesis entitled "Physico Chemical
Studies on Metal Chelates of Nitrogen and
Sulphur Containing Ligands" is the'result
of original^ researches carried out under
my supervision by Mr, Sartaj Tabassum and
is suitable for submission for the award-
of Ph.D. degree of Aligarh Muslim University,
Aligarh.
( K.S. Siddiqr)
ACKNOWLEDGEMENT
The author takes the opportunity to express his
special appreciation to Dr. K.S. Siddiqi, M.Sc, Ph.D.
(Alig.) for his perennial help and scholarly guidance
and to Professor S.A.A. Zaidi, for his valuable advice
throughout his course of work.
Prof. S.M. Osman, the Chairman, Department of
Chemistry is thanked for providing research facilities.
I am extremely beholden to my parents for their
affectionate encouragement and interest in my academic
pursuits.
The author is especially thankful to Dr.(Mrs.)
Rukhsana Ilyas, Dr. Noorul Hasan Khan and all colleagues
for their assis1:sQace and cooperation. Lastly I am also
thankful to Mr. Badar Afroz for typing. Financial
assistance from C.S.I.R. (New Delhi) is gratefully
acknowledged.
( Sartaj Tabassum )
C O N T E N T S
Page
Publications
List of Tables
Abstract
Chapter I :
Chapter II :
Chapter III :
Chapter IV
Chapter V
Chapter VI i
Chapter VII:
Introduction
Experimental Methods
Studies on complexes of
Barbituric acid, 5,5-diethyl
barbituric acid and thiobarbi-
txiric acid with lanthanide ions.
Characterization and Toxicity of
lanthanide complexes with Nitrogen
and Sulphiir containing Schiff
bases.
Raysiochemical and pesticidal
studies of lanthanide complexes
with Schiff bases derived from
aldehyde and dithiocarbamate
derivatives^
Synthesis characterization and
Toxicity o-f lanthanide complexes
with Schiff bases derived from
S. benzoyl dithiocarbazate and
aldehgrde.
Stxidies on complexes of
laflithanide(lll) with substituted
thiazjolidin-4-ones.
i-v
1-12
13-18
19-43
44-60
. 61-73
. 79-102
. 103-122
References' 123-131
P U B L I C A T I O N S
PUBLICATIONS
1. Studies on complexes of thiobarbituric jind 5,5-diethyl
barbituric acid with lanthanide ions.
S. Tabassum, K.S. Siddiqi, N.H. Khan, R.I. Kureshy and
S.A.A. Zaidi, Indian J. Chem. 26A, 489 (1987).
2. Sttidies on Barbituric acid complexes of lanthanide ions,
S. Tabassum, K.S. Siddiqi, N.H. Khan, R.I. Kureshy and
S.A.A. Zaidi, Indian J. Chem. 26A, 523(1987).
3. Characterization and toxicity of lanthanide complexes
with Nitrogen and Sulphur containing Schiff bases.
K.S. Siddiqi, S. Tabassum, R.I. Kureshy, N.H. Khan and
S.A.A. Zaidi, Inorg. Chim. Acta, 152, 95 (1988).
4. Riysico chemical and pesticidal studies of lanthanide
complexes with Schiff base derived from aldehyde and
dithiocarbamate derivatives.
K.S. Siddiqi, S. Tabassum, N.H. Kheci, R.I. Kureshy said
S.A.A. Zaidi, Polyhedron (Commxanicated).
5. Synthesis, characterization and toxicity of lanthsiide
complexes with Schiff bases derived from S.benzoyl
dithiocarbazate and aldehyde.
K.S. Siddiqi, S. Tabassum, N.H. Khan, R.I. Kuresiiy and
S,A.LA* Zaidi, Synth. React. Inorg. Met.Org. Chem.
(confflEHiicated).
6. Studies on complexes of lanthanide(HI) with substituted
thiazolidin-4-ones«
K.S.Siddiqi, S. Tabassum, N.H. Khan, R.I. Kureshy and
S.A.A. Zaidi, Bull. des. Chim. Beiges.(communicated).
L I S T O F T A B L E S
LIST OF TABLES
1, Elemental analyses. Melting point and molecular weights
of Barbituric acid complexes,
2, Characterization data of DBA and TBA complexes,
3, IR spectra of Barbituric acid and its complexes,
A. IR spectra of Thiobarbituric-;5,5-diethyl barbituric
acid and its complexes.
5. Values of Nephelauxetic Etect {^-0)^ Nephelauxetic ratio
p, Bonding parameter b* and Sinha Covalency parameter
S% for Barbituric-, 5,5-diethyl barbituric-, and Thio
barbituric Acid complexes,
6. Log K, -AG values at 25°, 30° and 35°C.
7. Log K,-AG values at 25°, 30° and 35°C for DBA and TBA
coffiplexes.
8. Analytical data. Melting points and molecular weights
of the Schiff base I & II and their complexes,
9. IR spectr a of complexes of Schiff base I & II and their
assignments.
10, Electrtmic spectral data for Pr " , Nd " , Ho " & Er "
ctjinplexes of Schiff bases I and II,
11, Metal ligand stability constants at 25°, 30° & 35°C.
12, Percent Inhibition data of (a) Aspergillus flavus,
(b) A nigar and (c) Percent mortality and LD^Q values.
13. Elemental analysis, Magnetic moment and molar
conductance data for Schiff base A, B and their
complexes.
'\l^^ IR spectra of Schiff base complexes of (A & B) and
their assignment.
15. Electronic spectral data for Pr(lII), Nd(lll), Ho(IIl)
and Er(lll) complexes (A & B).
16. Log K, and -AG at 25°, 30° and 35°C.
17. Percent Mortality and LD^Q of cockroaches with a
corresponding concentration of the Schiff bases and
its complexes.
18. Analytical data. Magnetic moment and Melting points
of the Schiff bases (L^, Lp, L,) and its complexes.
19. IR spectra of Schiff base complexes of (L^, Lp, L-z)
and their assignment.
20. Electronic spectral data f-or Pr" , Nd" , Ho" ^ and Er" ^
complexes. Nephelauxetic parameter (^) covalency
parameter (S) and b*.
21. Log K, and -AG 25°, 30^ and 55°C.
22. Percent Mortality of cockroacbes at different concen
tration of Schiff bases and its complexes.
25. Percent Inhibition data of Schiff base and its
complexes, (a) A. flavus (b) A. niger.
24. Analytical data, Melting point & Magnetic moment
of substituted thiazolidin-4-ones and its complexes.
25. IR spectra of thiazolidin-4-ones coraplexes(I, II &
III) and their assignment.
26. Electronic spectral dai:a of Pr(lll), Nd(IIl) Ho(IIl) and
Er(JIII) complexes.
27. Log K, -AG at 25°, 30° and 35°C.
28. Percent Inhibition data (a) Aspergillus .niger
(b) Aspergillus flavus (c) Alternaria pori (d) Percent
mortality and LDCQ O^ cockroaches corresponding concen
tration of thiazolidin-4-ones complexes.
A B S T R A C T
ABSTRACT
Lanthanides which have incompletely filled 'f orbltals
present a very interesting chemistry in several aspects mainly
as a conjs&quence of their ability to expand the octet offering
possibilities of increased coordination number around them.
An added point of recent interest in their chemistry is the
findings that they have toxic behaviour towards animal and man.
In aqueous solution the coordination sites are occupied by
water molecules and coordination only by very strong ligand is
possible.
In addition, cumulative harmful effects oi lanthanides
are generally unknown, but in the light of the results obtained
from experiments on the effects of massively administered
quantities suitable preventive precautions .are undoubtedly
advisable. General effects of the dozes administered to
animals are hyperglycemia, decressed blood pressure and develop
ment of gi*anulomas. Lanthanides act as anti blood coagulant.
They accumulate chiefly in lever and eliminated very slowly.
Sulphur and nitrogen containing ligajids are known to
be toxic and their toxicity is enhanced after complexation
with metral ions. In view of this an attempt has been made to
characterize lanthanide complexes with such ligand and to study
relative toxicological behaviour of these ligands and their
complexes towards insects and fungi.
Chelates of barbituric-;(BA) 5,5-diethyl barbituric-,
(DBA) and thiobcrbiisuric acids(TBA) with La(IIl), Ce(IIl),
Pr(TII), Nd(lll), Sm(IIl), Eu(IIl), Gd(ni), Tb(lll), Dy(lll),
Ho(lII), Er(IIl), Yb(IIl) and Lu(lII) have been synthesized in
1:3(M:L) ratio. They have been characterized on the basis of
elemental analyses^ molecular weighi; determination, UV/visible-
and IR spectroscopy. "Hie pH-metric study carried out at three
different temperatures viz., 25°, 30°, 35°C and 0.1 M ionic
strength indicated that there is only one dissociable proton
in these acids. These chelates have been found to be electro
lyte in dimethyl formaraide. On the basis of formation
constants the metal ions have been arranged in the order;
La< Ce< Pr< Nd < Gd < Er <Sm<: Eu<Ho<: Dy<iTb< Yb (BA)
La < Ce < Gd < Dy < Pr < Dy < Nd <i Sm <Ho < Er <: Eu <: Yb <: Lu (DBA)
La< Ce <Gd <Tb<i Pr< Nd< Sm< Dy< Ho<Eu<Er<.Yb CLu (TBA)
La(IIl), Ce(IIl), Pr(lll), Nd(III), Gd(lll), Dy(lll),
Ho(lII) and Er(lll) ctnnplexes of Schiff bases derived from
sulphamethoxazole and salicylald£fcyde(l) and -thiophene 2-
aldehyde(II) have been characterdzed on the basis of IR-,
NMR-, UV-visible spectroscopy, elemental analyses, conductance
measxirements and molecular weight determination.
The Schiff bases act as monobasic bidentate ligands. The
equilibrium constant has been studied in solution at 25, 30
ii
and 35°C. The nephelauxetlc effect (1-^ ), bonaing
parameter(^), b* and Sinha covalency parameter, 6 have been
calculated. The positive values indicated the covalent
nature of metal-ligand bond. "Rie covalent nature of the
complexes has also been supported by molar conductance
measurement. The toxicity of the Schlff bases and their
complexes were evaluated against insects. The LD^Q value
of cockroaches and % growth inhibition of the fungi shoved
that the toxicity is enhanced after complexation.
Synthesis of the ScMff bases derived from S-benzoyl
sulph«nilamide dithiocarbamate and thiophene 2-aldehyde and
4-N, N-dimethyl amino benzaldehyde has been carried out.
Their complexes of the type (ML).CI .ZHpO where M=La(IIl),
Ce(lll), Pr(lll), Nd(lII), Gd(IIl), DyCUIl), Ho(lll),
Er(lll) and Yb(III)^ have been characterized by IR-, NMR-,
UV/visible spectroscopy, elemental analyses magnetic moment
measurement. The nephelauxetlc effect (1 -^), bonding
parameter, R , b* and Sinha covalency parameter^ S and
the molar conduci;ance measxireraent in nitrobenzene reflect
covalent nature for the complexes. The equilibrium constant o
and thermodynamic data hawe been s1;udied in solution at 25,
30, 35 C. LogK has been found to be inversely proportional
to temperature. The toxicity of the schiff bases and their
complexes were evaluated against insects and fungi. The LD^Q
for cockroaches and % inhibition in growth of the fungi showed
111
that complexes are more toxic than Schiff bases.
Some new 0:N:S and N:S donor ligand namely, S.
benzoyl N-(N,0-hydroxy benzaldehyde) dithiocarbazate (L^),
S. benzoyl N-(N, N-dimethyl amino benzaldehyde) dithio
carbazate (Lp), S. benzoyl N- (N-thiophene 2-aldehyd«)
dithiocarbazate (L-,) and their complexes with La(IIl),
Ce(lll), Pr(lll), Nd(IIl), Sm(lll), Gd(lll), Tb(IIl), Dy(lll),
Ho(lll), Er(lll), Yb(IIl) and Lu(lll) have been synthesized.
The characterization has been done by known physical methods.
The molar conductance measured in nl1:robenzene suggest their
covalent nature and magnetic moment values exhibit paramag
netism. The values of log K and -<^G have been calculated
pH-metrically. The log K values for the complexes with Schiff
bases fo?.low the order L^> Lp ^ L^. Toxicity of the compounds
has been evaluated against cockroaches and fungi(Aspergillus
flavus and Aspergillus niger). 'Dxe LDCQ and % inhibition
obstensibly demonstrate great;er efficacy for the complexes
than for the free bases.
Reaction of CyclopentanoTie-(I), 2,2-disubstituted
methyl propyl-(II), 2,2-disubstituted hexyl ittethyl(IIl)
thiazolidin-4-ones with lanihanide(IIl) ions yield complexes
oS the compo-sltion M(L),.2HpO.
The structural elucidation of the chelates is done
by elemental analysis, IR-, NMR- and electronic spectroscopy,
magnetic and conductance measurement. These studies are
indicative of their covalent nature. From solution studies
iv
log K values appear to be inversely proportional to
temperature. In addition, the toxicity of the organic bases
and their corresponding complexes has also been investigated,
There is shear evidence that the metallation of the ligand
pronounces the toxicity >^ich is also reflected from
LDc-Q values. They also act as growth inhibitor in the case
of common fungi.. On the basis of the mortality data the
thiazolidin-4-ones may be arranged in the ascending order
of their toxicity.
H I - II < I
It has been noted that the compounds containing
methyl group cause an increase in fungicidal properties.
The fungltoxicity of the ligands follow the order:
UI^w/II > I
which is exactly the reverse to those found for insects.
CHAPTER - I
I N T R O D U C T I O N
1
INTRODUCTION
The inherent tendency of lanthanides to expand
their coordination number greater than six has been
extensively studied by different workers . The majority
of such lanthanide complexes involve nitrogen and oxygen
containing ligands while relatively very little work
has been reported on the sulphur ligated complexes of the Q in
rare earth metal ions- ' . This is probably due to the
larger ionic radii of the metal ions and the lower electro
negativity of siilphur atom, which result in the formation
of weak complexes.
Recently, lanthanide(III) chelates of 4-N(2'-
hydroxybenzylidene)-aminoantipyrin€ , imino acetic acid,
12 pfathalic acid, malonic acid , cyclohexane diaminotetra
acetic acid, 8-hydroxy quinoline-5-sulphonic acid ,
13 salicyloyl hydrazide, anthranilic acid , amino benzylidene,
14 benzidine have been characteriz.ed on the basis of IR~,
UV-VIS spectroscopy and magnetic measurements. Thermodynamic
si:gbility constants of lanthanide chelates with N-acetyl-
15 acettmylidene-orthanilic acid have tmen determined pH-
metrlcally at various ionic strengths and follow the order
La > Ce > Pr > Nd > Sm > Gd > Tb > Dy > Ho. The magnetic-,
conductance measurement and IR spectral data suggest the
following structure.
2
, ^ CH3,
H ^CH3
Lanthanide complexes of general formula Ln(p-TSO)Q
(010 )3 ( La = La - Lu, p - TSO = di-p-methyl phenyl 16
siolphoxide) were synthesized and characterized by chemical
and thermal analysis, magnetic moment and IR spectra, molar
conductance and molecular weight d«teniiination. Thermal
decomposition in an air stream, of these complexes led to
the formation of pvire lanthanide oxysulphate at 900 C.
17 Lanthanide furan 2-carboxylates of the type
Ija(CcH,0,)-, have been found to show some covalent character 0 z> D D
as compared to aquo ions. Thermogravimetric studies showed
that lanthanide complexes eliminate OH, OCH, and C^HcOH at
low temperature v^ile spectroscopic results suggest the non 18 involvement of phenolic oxygen
The metal ligand stahili ty constant of Ln(IIl)
1Q chelates off(carboxy methyl thio) succinic acid have been
determined at 20°C,25°C, 30°C,' 40°C and /t= 0.1M ionic
strength. The thermodynamic function for formation of 1:1
and 1:2 complexes(M-L) have been obtained by the temperature
coefficient method. The chelates are both enthalpy and
entropy stabilized. The A H and A S values have been
further analysed in terms of electrostatic and non-
electrostatic points. From the relative magnitude of A G
electro-and A G non electro values it is concluded that
electrostatic forces are stronger than the non electro
static forces in the formation of complexes.
Since the naturally occurring purines and
pyrimidines' occupy an important place in chemistry of life
processes a systematic work has been done on sulphur
20 analogues of naturally occurring purine ar c pyrimidine bases
A few compounds have been reported to be useful in chemotherapy
21 of cancer. For example, 6-mercaptopurine and 6-methyl
22 roercaptopurine have been found to have extremely clinically
useful aartileuk nic activity. In the pyrimidine group 2-
thiouracil was f.aund to produce transient Improvement in
23 chronic granulocyto leukemia .
Because of their application in the treatment of
thyx^otaxicosis 2-thiouracil and its alkyl homologues have
2A becoaie wellknoiwi . They play a significant role in drugs
and are a1 so used as s-tarting materials in the synthesis of
some organic chemicals. Their derivatives are used as
hypnotics. They are also used as an analytical reagent in
the determination of peroxide in blood serum.
4
Early in the history of barbituric acid synthesis
a few ol the 2-thiobarbiturates were prepared for the
purpose of converting * them into their oxygen analogues
and to study their toxic character. Two separate groups of
workers * reported independently the preparation and
pharmacological properties of a number of 2-thiobarbiturates.
They found that these compounds have, in general, a rapid
onset of action and were destroyed much more rapidly in the
body than were their oxygen analogues. Because of these
properties the thiobarbiturates are proving very successful
intravenous anaesthetics. Besides being a potential coordi-
na'tion ligand barbituric acid and thiobarbituric acid are
also known to be mildly toxic to most non ruminant mammals 29
e.g., rats, mice and pigs . However, mice were more sensitive
to thiobartrituric acid than barbituric acid, nevertheless,
barbituric acid causes physiological changes in lever and
kidney. Its depilatory action has been demonstrated in several
experiments on mice. Thiobarbituric acid has no cumulative
effect but it effects lever, spleen and kidney i"n mammals.
The maxi-muffi permissible limit of tolerance of barbituric acid
is 2,5 mg/ar. Some pharmacolo^cal investigations of
5-oxylldine barbituric acid containing different alkyl/aryl
chloro acids, on central nervous system have shown irregular
behaviour .
5
NXCOOK 0'
Complexes^'' of Co(ll), Ni(Il), Cu(Il) with
barbituric acid and thiobarbituric acid have been
reported to have varying ratio of upto 1:3. They have
further been characterized by electronic spectra, and
magnetic succeptibility measurement studies.
Coupling behaviour of (barbiturate)2-carboxy
methyl amino 5-ethyl-'5(l-methyl butyl barbituric acid)
with bovine serum albumin by active ester method has been
33 investigated .
,H—^ /Et
HO-C-H^C-t
N — ^ \CHM^,Pr H '0
A perusal of current chemical literature shows
that no systematic work on the rare earth chelates of
barbituric acid derivatrives has been reported. The diverse
properties of barbituric-, 5t5-dlethyl barbituric- and
thiobarbituric acid as medicine and as a potential metal
chelate motivated us to undertake the study of barbituric
acid, 5,5-diethylbarbituric acid and thiobarbituric acid
complexes of lanthanide(lll) ions viz., La(lll), Ce(IIl),
6
Pr(lll), Nd(lll), Sm(lll), Eu(IIl), Gd(lll), Tb(lll), Dy(lll),
Ho(lll), Er(lll), Yb(lll) and Lu<IIl). They have been
characterized on the basis of elemental analysis and various
physjcoch^mical studies like IR-, UV-VIS spectroscopy and
conductance measurements. The nephelauxetic effect(1-^ ) and
nephelauxetic ratio, ifi) have been calculated. The
complexation equilibria have been studied in the solution
state also. IHie stability constants of barbituricr,5,5-
diethyl barbituric-,and thiobarbituric acid complexes were
determined pH-aetrically at 25°C, 30°C, 35°C and 0.1M ionic
strength.
Many active Sulfonamide drugs are used in dye stuff
chemistry. It has been reported that acidwool dye stuff
containJTTg ttils groi; ) were particularly fast to laundering,
bleaching and lij^t, a criterion of strong affinity for
protein molecules. In the course of preparing several
sulfonyl azo dyes the historic drug 2,4-diamino 4'-
sxilfonylazobenzene hy-drochloride_,commercially known as
'Rrontocil^ vas discovered.
HC1^H20 -^^ A-»=N-^v /VSO2NH2
Domagk showeti that the animals infected with
hemolytic streptococcusB could be treated successfully with
this compo\jnd . A series of thiadiazole sulfonamides and
7
some compounds with considerable effect on the enzyme
activity in vitro do not have corresponding diuretic
potencies. In benzothiazole derivatives ttiis activity is
due to rapid metabolic degradation.
S02tfH 2
The 6-ethoxy derivative of this compound is more resistant
to metabolic degradation bxrt gives rise to side effects.
Et0'^^^-^^S'^S02N+«12
Blocking one of the two acidic centres in acetazolamide by
35 methylation enhances in vitro activity .
0 N N ^he-N_^N
" il JL " 1 1 M€-C-N^\ /^S02NH2 M^C-mi^^^/^ SO2NH2
These compoiinds penetrate tke eye aaud the brain faster
than acetazolamide and threrefore, may be used as anticon
vulsants and in the treatment of glauco^i.
Since it has been investigated that aromatJLc amines excreted
as acetyl conjugates, the conclusion we.s that the active
constituent of Prontocil was sulphanilamide.
" 2 ^ \ > •SO2NH2
8
Sulphanilamide was then prepared and administered to
infected animals. It showed high in vivo activity.
The medicinally important compounds having Schiff
base structure have also been intensively investigated,
lliey play an active role as analgesic, antiinflammatory,
antibiotic, antimicrobial and especially as anticancer
"56-43 drug . Their activity has also been reported to be
44-46 enhanced after complexation with metal Ions . Depending
on the position and nature of the heteroatoms, the 47-40
sulphonamide exists in amido and mi do tautomeric forms
This form may change during Schiff ba&e reaction.
-SO2- NH - C=N ^ -SO2 - N=C - NH
amido imido
Obviously the coordination abilit;y of botti these forms
varies from one another* Sulphamethixole changes fvxxm imido
to amido form during the Schiff base reaction and again to
50 imido form upon chelation , because th€ SD^ groi^ of
sulphonamide is knovm zo be a weak chelat:bag agentr .
In the past two decades the sxdi±ff bases dHrived
from aromatic atlde hydeis and afflid«=s have a-ssufflead great
importance in the preparation of pharmaxyeuti_cal agents
The polarographic studies ^ on the trivial divalent
transition metal complexes with Schiff bases derived from
fl
sulfafurazole, sulphamethizole, sulphamethoxy pyridazine
and salicylaldehyde are extensive while the solution studies
are scarce * ^. A thorough survey of the chemical literature
revealed that no work has been done on lanthanide complexes
of schlff bases derived' from sulpha drug and aldehydes.
The research in coordination chemistry of Schiff
bases essentially deals with the properties and the structure
of their metal chelates. Nevertheless, the recent advances
70-72 made in this field have shown that in addition to the
above properties the schiff bases are important from 7-5
biological view point . Thus extensive application of
these Schiff bases and their complexes have been made in
diverse fields such as medicine, pharmacology ~ and in
affialysis. In view of this an attempt has been made to
syntiiesize and characterize the schiff bases (by the
interaction of sxolphamethoxazole and S-benzoyl sulphanilamide
di^thiacarbamate on aldehyde) and their complexes with
lanthanides. Further, the pesticidal nature of the free
and compl exed biases against cockroaches and fungi has also
bseen explored besides their physicochemical studies.
Stability caanstant of the complexes formed in solution has
been calculated at three different temperatures viz.^ 25, 30
and 35°C.
Study of metal dithiocarbamates is an interesting
field of research because of their wide application
10
as pharmaceutical, fungicidal and analytical reagents. They
are also used in the stabilization of transition metals in of.
higher oxidation states . Moreover, the work on dithio-
carbamate derivatives such as carbazates and their
corresponding Schiff bases has not received much attention
although, the interaction of metal ions with sulphur and
nitrogen containing organic moieties has been thoroughly 70 ft7—RQ
investigated owing to their biocidal activity * " . Such
work is generally limited to the transition metal complexes
90 with these Schiff bases .
In the present work a dithiocarbamate from hydrazine
was converted to dithiocarbazate which was further converted R1
to schiff base by the trivially known procedure . The
tridentate Schiff bas€S containing NNS donor groups have been
employed in complexation with transition metal ions but the
study of Schiff bases containing QNS donor groups has
received less attention. An attempt has therefore, been
made to study the nature and complexing behaviour of Schiff
bases derived from S-benzoyl N-(N,0 - hydroxy benzaldehyde )
dithiocarbazate, S-benzoyl N-(N,N, dimethyl amino
ben2ialdehyde) dithiocarbazate, S-benzoyl N-(N-thiophene 2-
aldehyde) dithiocarbazate. The interaction of these ligands
with lanthanide(IIl) ions in solution as well as in solid
state has been investigated. The stability constant of the
complexes has been studied pH-raetrically,
It
Toxicity of the free base and their complexes has
also been investigated in several sets of experiments
against insect and fungi.
Having multiple coordination sites thlazolines and
thiazolidinones may be exploited as strong donor on one hand,
and by virtue of their sulphur contents they may be examined
91 for their toxicity on the other. Singh and Coworkers have
outlined a variety of methods for the synthesis of several
thiazolidinone and their derivatives. The studies on the
complexes of thiazolidin 4-ones are rare althou^ the study
of their biocidal activities are appreciably substantial.
92 95 Divalent transition metal complexes ' of thiazolidinones
94 have widely been used as stabilizer for polymeric materials
and exhibit miticidal, pesticidal, bactericidal, fungicidal,
95 94 insecticidal tuberculostatic and antlinflammatoTy activities ' ,
'Ehe stereochemistry of thiazolidinone is important due tx) the
presencie of multifunctional groups like carbonyl oxygen,
nitrogen and sulphur atoms.
Recently, some group(lV) and organotin(lV)
deri"vatirves * of cyclohexanone spirothiazolidinone, 3-
aminorhodanine, 2,2-disubstituted ethyl methyl-, 2,2-
disubstituted methyl pentyl-, 2,2-disubstituted acetophenone
and 2,2-disubstituted benzophenone have been reported from
this laboratory. They have been found to be lethal for
cockroaches and fish.
?
From a survey of chemical literature it appears
that the complex forming ability of 2,2-<iisubstituted methyl
propyl-, 2,2-disubstituted hexyl methyl- and cyclopentanone
thiazolidin 4-ones with lanthanide ions has not been
investigated. It aroused our interest to carry out such
Investigation with La(lll), Ce(III), Pr(ni), Nd(III),
Sm(lll), Gd(lll), Dy(lll), Ho(ril), Er(lll), Yb(lII), Lu(lII)
chloride to ascertain the mode of coordination. As the
complexes and the ligands contain sulphur atoms they are
anticipated to be fairly toxic. A comparative study of the
toxicity of various thiazolidin-4-ones and their complexes
has been done on cockroaches. Their percent mortality and
LDcQ values are calculated by graphical method . All
thiazolidin-4-ones and their complexes have been investigated
for their fiongitoxicity in terms of % inhibition in growth of
the fungi.
CHAPTER - I I
E X P E R I M E N T A L M E T H O D S
13
EXPERIMENTAL METHODS
The physico-chemical methods used for the structural
elucidation of nevly synthesized ligands and their complexes
described in the present work are infrared-, nuclear magnetic
resonance-, UV/Visihle spectroscopy, conductance-, pH-metric
measurements, magnetic moment and molecular weight determina
tion. To investigate the toxicity of the ligands and their
complexes in termsof LDc« the graphical method has been used,
98 while the f\angitoxicity determined by agar plate method .
Toxicity and probit analysis;
In order to find out the toxicity of a chemical in
terms of probit the effect of the stimulus is determined
according to the reaction of living organism against that
chemical. Usually the stimulus is applied at a series of
experimental range and the reaci ion of each range determined
from its application to a set of experiments.
Instead of speaicing in general term, it is more
convenient in descriTjing the kind of data to refer to one
type of experiment srich acs the determination of the toxicity
of a chemical formulation to a given type of insect. In
such experiments various concentrations of the compoxmd are
prepared and a set of insects assigned at random to each
concentration level. The compound is applied, and fcr each
set a count is made at the total number of insects(n) and
14
number killed(r). The results can be expressed either as a
proportion (r/n) or as a percentage 100(r/n). Such data may
then be applied for probit analysis is assessing the various
toxic substances and lethal doses-.
Tolerance limit
For any one subject there is a certain level of
intensity of the stimulus below which response does not occur
and above which it does occur. For example, in considering
a given insect there is a limit of concentration for a
certain chemical such that if the concentration is below
this limit the insect will survive, but if the concentration
exceeds this limit the insects will di-e« This tolerance is
represented by ^ , For most; of the biological preparations
the distribution of A is not normal but is at least
apprt)ximately normal for X = log .. In probit analysis,
therefore, th^ log of the concentration is usually used. .1
Following Finney >, is referred to as the dose in terms of
actual concentration expressed in milligram/litre and the
log..Q concerrtration is referred to as the d£)sage. A plot
of the percentages killed against dosage gives a sigmoid
curve. The analysis of results from the sigmoid ctirve
presents some rather serious difficulties. It would
therefore, seem to be desirable to use a transformation of
the percentages such that with a normal distribution the
transformed percentages would lie in a straight line.
IT)
Any variation from the normal curve will cause the plotted
probits to vary from a straight line. Generally, the
observed variations from a straight line are of two types,
(I) In the first place the sets of experiments may not be
all uniform or the conditions for the sets may not be
uniform. This will tend to produce an abnormal scatters of
the points about the straight line.
(II) In the second place the transformation of the dose to
dosage may not be siiltable.
Practical application of probit analysis;
Since we expect to get a straight line when
probits are plotted against dosage, the methods of linear
regression are suggested.
To measure the potency of the preparation it has
been found that the dose giving a 50% kill is the most
statistic and referred to as LDc- (median lethal dose). In
experiments where the response is not death we refer to
the ETUQ (median effective dose). Whatever practical
advantages there may be in knowing the LDQQ or som e similar
value, the fact Is that much greater precision can be
obtained in the measure of the LDc j which is corresponding
to a probit value of 5.
Another factor to be measured is the range of the
dosage required for a given range of percentage kill.
IS
This might be referred to as the sensitivity of the
preparation tested. Obviously, if small changes in
concentrations give wide range in the percentage kill, the
sensitivity is high and represented by the slope of the
line. The greater the slope the narrower the range in
dosage for a given range in the percentage kill.
The geometry of the line would seem to give,
therefore, the required measure of potency and sensitivity.
Taking two points X and Xp, representing the dosage, on
the abscissa of the graph and finding the corresponding
points Y^ and Yp on the probit scale, will give the slope
of the line. If b represents the slope, then
b =
Y - Y
X2 - X
This makes it possible to set up a regression
equation of the type Y = a + bx where a = Y^ - bX^ or
Y2 - bX2.
Fungitoxlcrityt
In ordaar to e-valuate the fungitoxicity by Agar
plate technique a medium was prepared by the following
method.
• I
4
Preparation of potato-dextrose-agar(P.D.A)
Peeled potatoes(200 g) were boiled in 500 ml of
water. Extract was mixed with 20 g agar and 20 g glucose
in 500 ml of water. After mixing the voliirae was made upto
1000 ml in Erlenmeyer flasks. The flasks were plugged with
non absorbant cotton. The medium thus prepared was
sterillized for 15 minutes at 15 lbs pressure in autoclave,
Sterillization of petridishes
The pei;ridishes after having cleaned were wrapped
with papers and were transferred in oven at 180 for one hour.
Isolations of fungi
The vegetables, fruits and slices showing infected
areas were removed by sterile scalpel and transferred in
the petridishes containing P,D.A. The fungi appearing in
these petridishes were isolated in pure culture. The
inoculum was raised on P.D,A. by transfering mycellia from
the pure culture.
The compxDunds were screened for their antifungal
activity against A. flavus and A. niger by agar plate
technique at three different concentration viz. 1%, 1.5%,
2% ..,,, Two commercial fungicides Memege and Blitox 50 WP
have also been tested under similar conditions to compare
the results. The niimber of replications in each case was
three.
n
The % inhibition in growth of the fungi was
calculated by using the following formula.
% inhibition = ( ^ ~ ^ ) X 100 C
Where 'C diameter of fungus colony in control 'T' diameter
of treated fungus colony after 96 hrs.
CHAPTER - III
STUDIES ON COMPLEXES OF BARBITURIC ACID, 3.5-
DIETHYL BARBITURIC ACID AND THIOBARBITURIC
ACID WITH LANTHANIDE IONS.
19
STUDIES ON CONPLEXSa OF BARBITURIC ACID,. 3, -DIETHYL
BARBITURIC ACID AND THIOBARBITURIC ACID WITH LANTHANIPfc IONS.
Experimental
Materials and methods;
The rare earth chloride(Reagent grade or May & Baker),
NaOH, NaClO^ (Riedel), HCIO^(E.Merck), barbituric acid, 5,5-
diethyl barbituric acid, thlobarblturlc acld(Koch light) were
used as such.
The IR spectra(600-4000 cm ) were recorded on a
Perkin Elmer 621 spectrophotometer as KBr disc and UV/vlsible
spectra on a Pye Unlearn PU 8800 spectrophotometer. pH-metrlc
titration were done using an Ellco pH-meter model LI-10T.
All the calculations were done on a computer model Digital
VAX/l1-7aO.
Synthesis of the Complexes;
A typical method of synthesis of the complexes is
outlined 1^1 ow.
BiaTiDituric acids(0.03 mol) dissolved in 20 ml water
or ethanol were mixed with lanthanlde(IIl) chloride(0.01 mol)
solutions. The mixture was stirred for 4-5 hrs on a water
bath. On standing for 12 hrs at room temperature an
amorphous powder was obtained. It was washed with ethanol
and dried in vacuo.
20
For the pH-metric measurement Bjerrum Calvin pH-
metric titration technique as modified by Irving and Q Q
Rossotti was employed. Solutions of barbituric acid, 5,5-
diethyl barbituric acid and thiobarbituric acid, NaOH, NaClO,
and HCIO/ were prepared in CO^ free doubly distilled water.
In order to prevent hydrolysis, the metal(lll) chloride (0.005 mol) solutions were prepared in HClOi. The
experiments wen
ionic strength.
experiments were carried out at 25°C, 30°C and 35°C at 0.1 M
2i Results and Discussion
Barbituric acid(BA), thiobarbituric acid(TBA) and
5,5-diethyl barbituric(DBA) exhibit tautoraerism but only one
of the two forms in each case is predoininant(I, III, V).
0 OH
r^N-H AN "^N^O HO-^N-^°
(I)
(BA)
(II)
I
H
SH
(III)
C2H5 C2H5
H
(TBA)
(IV)
HO N'
(V)
(DBA)
(VI)
The existence of form I, III and V has been
ascertained on th€ basis of halogenation reaction *
The bromination in water of barbituric acid and related
compounds is abnormal. Barbituric acid yields 5 mono
bromo- (D) and 5,5-dibrorao barbituric acid(E).
OH
Br
(D) (E)
The mechanism of the formation of (E) is unknown
but it could be an addition of HOBr to the 4,5-bond of the
monobromo derivative(D), followed by dehydration.
The analytical data(Table-1 & 2) indicated that
the complexes isolai;ed in the solid state are of the type
M(L)^.2H20 v jere M = Lanthanide(lll) ion and L = barbituric
acid, thiobarbituric acid and diethyl barbituric acid. These
acids are deprotonated in soJLution and behave as uninegative
bidentate liganxi. In the coinplexes the chloride ion is
removed as HCl >±iich has been confinned by a negative test
of chloride in complexes. "Dae molecular weight of the
complexes determined by viscosity measurements are very
close to those calculated(Table 1,2), The molar conductance
value of millimolar solution of these complexes in EMF (68 -
3
Table 1 - ii:]"iTi.nitrU Anal VM-.^ melting points and mole, weights of
BHrbJtur'ic ar-jd c(.'nii)Iexes.
;;T Barbj Luri c Acid Complexes
Colour'! C % Calc. (b ound)
M.P, Molar Conductance
Ohm'^ Cm^ raol" '
Molecular weight
La(BA)-,.2H20
Ce(BA)^.2H20
Pr(BA)^.2H20
Nd(BA)^.2H20
Srn(BA),.2H20
Eu(BA),.2H^0 5 ^
Gd(BA)^.2H„0
Tb(BA),.2H20
Dy(BA)^.2H20
Ho(BA)^.2H20
Er(3A}^.2H20
Yb(BA)^.2H,0
Light Yellow
Lir:ht yellow
Yellow
Yellow
White
Light yellow
Light yellow
Light yellow
Yellow
Yellow
Yellow
Yellow
25.87 (26,53)
25.86 (26.25)
25.82 (25.70)
25.67 (25.75)
25.39 (25.55)
25.32 (25.50)
25.09 (25.10)
25.01 (25.15)
2^.86 (25.20)
24.76 (24.82)
2^. oo (24.70)
24.39 (24.40)
2.35 (2.24)
2.35 (2.25)
2.34 (2.28)
2.33 (2.29)
2.30 (2.20)
2.30 (2.25)
2.28 (2.30)
2.27 (2.22)
2.26 (2.23)
2.25 (2.20)
2.24 (2.19)
(2.15)
275
260
265
270
280
265
265
290
260
290
280
285
68
68
68.5
80
85
80
90
75
85
85
90
556.04 (530.00)
557.25 ^50.00)
558.03 (552.00)
561.37 (540.00)
567.48 (548.00)
569.09 (545.00)
574.38 (574.38)
576.05 (554.00)
579.63 (559.00)
582.06 (572.00)
584.39 (570.00)
590.76 (571.00)
Table 2 - C h a r a c t e r i z a t i o n u a t a o i hhP- ana I'hf^ Corru lexe:- , 24
Complexes
La{DBA)^
Ce(LB;i)^
PrCDBA)^
Nd(BBA),
Sm(DBA)^
Eu(DBA)^
Gd(DBA),
Tb(D3A)^
Dy(DBA)3
Ho(DBA)2
Er(DBA),
Yb(DBA)^
Lu(DBA),
La(TBA)^
Ce(TBA),
Pr(TBA)^
1 i Colour i (m.po, C)
1 Colourless (240)
Colourless (280)
Green (240)
Voilet (250)
Colourless (245)
Colourless (230)
Colourless (230)
Colourless (235)
Colourless (260)
Pin]< (240)
Colourless (235)
Colourless (240)
Colourless (245)
Yellow (255 d)
Yellow (260 d)
Yellow (268 d)
Caleb
C
41.85 (41.12)
41.80 (42.10)
41.75 (42.00)
41.55 (41.80)
41.19 (41.50)
41.09' (41.25)
40.78 (41.20)
40.92 (40.80)
40.43 (40.60)
40.35 (40.50)
40.21 (40.^0)
39.89 (40.00)
39.79 (40.00)
25.37 (26.00)
25.32 (25.30)
25.28 (25.80)
lated (round) h
H
4.82 (4.90)
4.81 (4.85)
4.81 (4.84)
4.79 (4.80)
4.74 (4.80)
4.73, (4.81)
4.70 (4.75)
4.69 (4.79)
4.66 (4.75)
4.65 (4.75)
4.63 (4.70)
4.59 (4.65)
4.58 (4.65)
1.59 (1.71)
1.59 (1.32)
1.59 (1.70)
S
-
-
-
-
-
-
-
-
-
-
-
-
-
16.93 (16.80)
16.89 (16.75)
16.87 (16.90)
. Molecular i \ » / ^ 1 rrrl "1"
1 (670.00)
689.53 (665.00)
690.31 (670.00)
693.65 (670.00)
599.76 (675.00)
701.37 (580.00)
706.66 (585.00)
708.33 (687.00)
711.91 (590.00)
714.34 (695.00)
716.68 (695.00)
722.45 (700.00)
724.38 (702.00)
567.88 (547.00)
569.09 (550.00)
569.87 (550.00)
Contd,
Table ? - continued 2S
Comnlexes i
1
Nci(T3A)^
3m(T3A)^
Eu(TB/.):
Gd(TBA),
Tb(TBA)^
Dy(TBA),
Ho(TEA)J
Er(TBA)^
Yb(TBA)^
Lu(TBA)^
Colour (m.p.,"C)
Yellow (270 d)
Yellow (265 d)
Light yellow (270 d)
Light yellow (265 d)
Yellow (275 d)
Yellow (265 d)
Yellow (280 d)
Yellow (268 d)
Light yellow (290 d)
Light yellow (280 d)
i "'-'-
\ c
25.13 (26.00)
24.87 (25.12)
24.80 (26.00)
24.55 (25.35)
24.51 (24.36)
24.36 (24.60)
24.26 (24.80)
24.17 (24.75)
23.95 (24.65)
23.86 (24.20)
lculated(Found) %
H
1.58 (1.71)
1.56 (1.70)
1.54 (1.65)
1.54 (1.60)
1.54 (1.53)
1.53 (1.60)
1.52 (1.62)
1.51 (1.60)
1.50 (1.60)
1.50 (1.55)
! ^
16.77 (16.65)
16,60 (16.65)
16.55 (16.40)
16.40 (16.30)
16.35 (16.30)
16.28 (16.20)
16.19 (16.00)
16.13 (16.20)
15.97 (15.7C)
15.92 (.15.70)
Molecular wej ght
573.21 (5^5.00)
579.32 (560.00)
580.93 (560.00)
586.22 (562.00)
587.89 (565.00)
591.47 (570.00)
593.90 (570.00)
596.23 (572.00)
602.01 (580.00)
603.94 (560.00)
2S — 1 2 —1 98 Ohm cm mole ) correspond to that of an uni-univalent
101 electrolyte . It may probably be due to solvolysis in
DMF.
O N O N
V V/s M • S >- M S a ^,..,^ (SOLVENT) ^^ r \
IR S p e c t r a :
The solution spectra of these barbituric acids
are only slightly different from those of the solid.
Barbituric- and diethyl barbituric acids have been reported
to exhibit three intense bands in the range 1690-1760 cm
assignable to i^C=0 although it is difficult to distinguish
between bonded and free CO group. In this case two bands
have been observed at 1690 and 1720 cm where the latter
shows a negative shift of 5 to 10 cm table 3,^ . Such a
small shift in iD C=0 may probably be owing to the coupling
102 of non bonded CO groups with those of the bonded ones ,
The N-H stretching frequency occur in the free ligands at
3180, 3150 cm . Only one of the two N-H bands appears
after complexation as a consequence of removal of hydrogen
as HCl. The NH deformation band coupled with >> (C-N)
appears at 1450-15^0 cm in the case of the complexes inferrini
I T a b l e f - ].K S p e c t i v , (•:! iv i r tn t ur-J t ;.(
-2 u o m p i e x p s
B a r b i t u r i c a c i d
L a ( B A ) ^ , 2 H ^ 0
C e ( B A ) ^ . 2 h . O
P r ( B A ) ^ . 2 H 2 0
N d ( B A ) ^ . 2 H 2 0
S m ( B A ) , . 2 H 2 0
E U ( B A ) ^ . 2 H 2 0
Gd(BA)^.2H2C
T b ( B A ) ^ . 2 K 2 0
Dy(BA)^ .2H2C
H o ( 3 A ) ^ . 2 H ^ C
£ r ( B A ) ^ . 2 H , 0
Y b ( B A ) ^ . 2 H 2 0
(N-H) - 1
cir
5180 (w) 3 1 5 0 ( 0 )
3180 (w) 2 9 l 5 ( m )
3'i&0(w) 2 9 l 5 ( m )
3,180(w) 2920 (m)
3 1 8 0 ( v ) 2 9 2 0 ( m )
3ieo(w) 2915(m)
3 l 8 0 ( w ) 2915 (m)
3 l 8 0 ( w ) 2920 (m)
31€E)(*) 2 9 1 5 ( m )
3 i a D ( w ) 2 9 2 0 ( m )
3:}d0(vi£} S l 5 ( m )
3 l 8 0 ( v ) 2 9 1 5 ( m )
31@0(n?) 2 9 2 0 ( m )
-<>(c=c) 1
err
16^-0 v j 1720 m
1 o 9 0 ( s ) 1710(rn)
l 6 9 0 ( s ) 1710(m)
I 6 9 0 ( s ) 1720(m)
1o99( f l ) 1715 (m)
I 6 9 0 ( s ) I 7 1 5 ( m )
1 D 9 0 ( S ) 1720(m)
I 6 9 0 ( s ) 1715(m)
I 6 9 0 ( s ) 1 7 2 0 ( w )
I 6 9 0 ( s ) 1720(rri)
I 6 9 0 ( s ) 1720(n])
1 6 9 0 ( 3 } 1715(m)
I 6 9 0 ( s ) 1 7 2 0 ( m )
S ( : - - ) ^ r ^ ( C - ! \ )
- 1 en
It-^-iOl A')
1535(m)
1 5 3 5 ( s )
1 5 3 0 ( s )
1 5 4 0 ( w , b )
1535(m)
1^335(111)
1 5 4 0 ( s )
1 5 3 5 ( n i , b )
1 5 ^ 0 ( s )
1 3 ^ v ( s )
1 5 A 0 ( s )
1 5 A u ( s )
oil
U h - ( w ) V'tUi ( >'v')
l r -9u( w) 1 - 4 v ; . V - V ;
V ' 3 . ( . v ) 1HOG(W)
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1283(w) lAOO(w)
1285(w) 1400(w)
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12b5(w) "1 ^ u G ( w )
1 2 8 : ( . ; I 4 J O ( / V O
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that cocrdination occurs with nitrogen atom. The sulphur
atom in TBA does not seem to be involved in coordination as
shown by the persistent appearance of "j)(C=S) in the region
1235-1240 cm in both the free and complexed ligand.
Moreover, the lanthanides being hard acids do not prefer
to bind with soft bases. It is therefore, concluded that
the barbituric acids coordinate only through the nitrogen
and oxygen atoms.
Absorption spectra
The absorption spectra of the complexes are
recorded in methanol. The intraligand transitions occur in
UV region. The sharp line due to Tf transition originating
with in the f configuration of lanthanide(IIl) ions are
effected by the influence of the ligand on complexation.
The shift of absorption bands to lower wave number is
103 usually of the order of few percent and is caused by a
decrease in interelectronic repulsion parameter in the
complexes. A red shift of f-f transitions would be observed
for these complexes as compared to the corresponding aquo
ions. Their red shifts have been ascribed to nephelauxetic
effect''° '''° , (1 -yS). The^ and (1 -^) values for Pr*^,
+3 +3 +3 Sm , Ho and Er complexes are presented in Table 5 «
The nephelauxetic ratio,/9 can be calculated from the relation,
n _ " Complex
S) aquo
tn 0) +J O 0) -H E t , (0 3 f-. +J a) -H ft X>
i-, bO CD C CQ
•H •o o O £
CQ E-(
• - d ^ ^ C • ^ CO
«w^ -O O -H
•H O +J CD CO U O
•H O f-.
•H D -P +J
:3 u CD CD
iH m 0) X: rH D, >^ 0) £ 2 -p
a; •« -H
^ Q
<*i. i n 1
T- i n
-P O "O 0) -H
VH O <H CD w
o O -H -H t^ -P 3 0) 4-> X -H D ^ CD t .
i H CO 0) cn x: ft U 0) o Z 'H
<H -a? o t© W T3 QJ C 3 to
l-{ CDr*>J
> XI
t
i n
0) rH J3 CO
£-1
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O
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m ON en o
CM 1 o T—
X o t ^
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E CO
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1 o T~
X ^f^
• o
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00 i>n
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t > CTs ON
O
CM 1 o r*~ X f n
o
o o
o
ON i n o o
m ON 0-'
o
CM 1 O T—
X ir-o
M l-H
t—1
o X
T-
o
I ^ o o
ON ON ON
o CM
1 o ~ X
o •
T—
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• o
CM CM o
• o
(JN ON ON
o
CM 1 o v X r—
o
o T—
o
CM CM O
O
ON ON ON
o
CM 1 o t—
X o — o
M 1—i t—1
u Cd
3^
34
Where -9 complex and -\> aquo are the energies of absorption
expressed in Kilo Kaisers. The nephelauxetic red shift
may be used, as a measure of covalency in the V L
bond. The positive values of bonding parameter for these
complexes indicate covalent bonding(Table-5). b* and B% are
expressed by the relations;
b^ = i (1 -^) *
S(%) = (1-^ /^ ) X 100
Proton llgand stability constants;
From the pH-metric titrations it has been found
that the acid ligand curve deviates from the pure acid curve
at pH = 2.5, 2.26 and 2.5 in BA, TBA and DBA respectively Fig.1
I I H H
(BA)
(DBA)
35
C7»
to Of
at
e I ex
t GQ
Acid alone
b Acid + Barbitunc acid
A Acid+Barbituric acid + m»tal ion
± _L X X ± 2 4 6
mis of NaOH
8
F I G . I T Y P I C A L T r T R A T f O N CURVES OF R A R E E A R T H ( I I I ) I O N C O M P L E X
3R
N* - N
A i
(TBA)
The proton ligand formation number nA were
calculated using lining and Rossotti equation(l), the proton H
ligand stability constant, pK^ were obtained(6.80, 6.'37 & 7.45) by
pointwise calculation using equation(2) and (3).
L (V^+V^) TL J
TL = ligand concentration
Y = number of dissociable protons
V = fixed volume 50 ml
V^= Volume of NaOH consumed in titrating pure acid,
Vp= Volume of NaOH consumed in titrating ligand + Acid
N = NaOH concentration
£ = Acid concentration
PK!J = pH + log (nA - 1/2-nA)
1 < HA < 2 (2)
pK2 = pH + log (nA / 1-nA)
1.0>HA (3)
3?
The highest nA value calculated at pH = 2.5 and 2o2 5
fall below unity clearly demonstrating the presence of only
one dissociable proton (0.93, 0.91 and 0.93).
Stepwise stability constant was calculated assuming
the absence of hydrolysis and the formation of polynuclear
species. The metal ligand titration curves deviate from
pure ligand curve at pH = 2.5 - 3.00, The metal-ligand
formation number, n was found, to be less than one which
suggested the formation of only 1:1 complexes. The values
of free ligand exponent pL were calculated at various n values.
Metal ligand formation curves were obtained by plotting
n versus pL (Table 6,7f Fig,2). From these curves, accurate
log K values was obtained by point wise calculation using
equation.
n = (V3-V2) (N° -H E^)
(V°+V2) nA X TM
J. anti
_
log Bn
(TL -
"x(
n
anti
. TM)
1 log
X
pH
yo
) X V° + "'1 PL = log^Q
TM = Metal ion concentration
V, = Valume of NaOH consumed in titrating acid + Metal +ligand
log K = PL + log n/1-n
A plot of log K^ vs e /r shows a roughly linear
relationship suggesting ionic character for metal ligand
bond (Fig.3).
:?8
<t e
Complex
P\, - A J an'^ vn lu f - ' at - r>Y, ^;0^'': a n r ')' ' I .
Lo- K
''O^n -7 c^'^r oc;' (
Laf^^T)
CP(ITI)
Pr(TTJ)
K'd(TIT)
sndii)
Eu(lII)
Gd(lll)
Tb(lII)
Ly(TTl)
Ho(lTI)
Er(lll)
Yb(lII)
'^J^Vj^.'^C
^.U9 + .'>0
^.'ji4+.?7
5.77^.28
4.21+.27
h. 26^.26
3.93+.20
4.32+.28
4.^1 + .30
A.27+.30
4.15+.25
4.65+.40
'..10+. 2 A
^.114-.28
^.^4+.26
3.38H:.?^
3.S1+.26
3.851.27
3.58+.24
3.77+.28
3.381.28
^.Q0+.26
3.761.26
4.02+.30
2.a«j-.26
".9I1.2S
.00_+.:'6
^c11l.24
3.37+.25
3.4^1.26
3.131-22
5.VV1.24
3.^41.28
3.44-f. 26
^.?7i.^A
3.5^+.25
4.72
4.74
4.-1
= .1"
5.72
5.7:,
5.34
5.8?
5.SC
= .81
5.5A
6.32
' i . 67
5
4.
4
c,
c:
3?
?4
."0
.26
./-^o
.19
J . , ' ,
'A.
A.
/^,
A.
/..
'^.
^
A
^
/
/-
A
- /
•- 2
^"7
73
70
39
83
34
84
. 59
Q2
39
T?ble 7 - Lo- K ann -AG at -) L n :/. ]<~)-
DBA Complex Log K
25°C 30 C 35^
-AG K Cal n.ol
-1
•pr -p 30 'C 3 ^ :
LB(TTI)
Ce(lTl)
Pr(lTl)
Nd(lll)
Sm(lll)
Eu(lTl)
Gd(lll)
Tb(IIl)
Dy(III)
Ho(TII)
Er(IIl)
Yb(III)
Lu(lII)
2.51+.13
2.58+.12
2.92+.10
3.03+.12
3.16+.13
3.20+.12
2.87+.10
2.97+.10
3.oo+.ir
3.19+.12
3.19+.13
3.20+.1^
3.25+.13
2.2»O+.10
2.42+.09
2.80+_. 12
2.95+.13
3.00_+.12
3.10+.13
2.75+.14
2.86_+.10
2.90+.13
3.00^^.10
3.06+.12
3.10^.'2
3.10+.13
2.35+.10
2.35+.10
2.70+.13
2.90+.12
2.95+.13
3.00^,14
2.65^.13
2.7C+.12
2.80+.10
2.95+.12
3.00^.12
^.•X4^.10
3.03+.1C
^.41
3.50
3.96
4.11
4.29
4.34
3.39
4.03
4.07
4.33
4.33
4.34
U.h^
3.31
^.3^
3.36
4.07
4.14
4.28
3.79
3.95
4.00
4.14
4.22
4.28
4.28
3.30
3.30
3.79
4.07
4.14
4.21
3.72
3.79
3.93
4.14
4.21
4.21
4.23
Contd....
Table 7 - continued
40
TBA Complex
La(lll)
Ce(lll)
Pr(lll)
Nd(lII)
Smdll)
Eu(lll)
Gd(lII)
Tb(lII)
Dy(lll)
Ho(IIl)
Er(lII)
Yb(lII)
Lu(lll)
25°C
2.A51.10
2.91+.13
3.05+.10
3.10+.1A
3.16+.16
3.28+.13
2.96+.10
3.00+.10
3.19+.13
3.25+.1A
3.30+.16
3.47^.20
3.47+.13
Log K
30°C
2.30^.10
2.80+.14
2.95+.12
3.00+.13
3.05i.lO
3.15+.12
2.90+.16
2.90+.10
3.10+.12
3.15+.13
3.20+.14
3.40+.13
3.40_+. 10
35°C
2.20+.10
2.70+.13
2.85+.10
2.90+.14
3.00+.12
3.05+.12
2.85+.10
2.85+.13
3.05+.12
3.10+.14
3.15+.14
3.30+.12
3.35+.10
(K 25°C
3.32
3.95
4.14
4.21
4.29
4.45
4.02
4.07
4.33
4.41
4.48
4.71
4.7
-AG Cal mcl ')
30°C
3.17
3.86
4.07
4.14
4.21
4.35
4.00
4.00
4.28
4.35
4.42
4.69
4.69
35°C
3.08
3.79
4.00
4.07
4.21
4.28
4.00
4.00
4.28
4.35
4.42
4.63
4.70
I c
PL F I G . 2 . TYPICAL FORMATION CURVE OF
RARE EARTH ( I I I ) tON COMPLEX OF BARBITURIC ACID .
5.0
o o in
1-< iC
6 o
4.0
3.0
2.0
1.0
0.0
5.0
o %n CM 3.0
<
o o
2.0
1.0
0.0
• •
8.5 -L
9.0 9.5
( T B A )
10.0
_L 8.5 9.0 9.5
( D B A )
10.0
10.5
10.5
i?.
5.Or
o 4.0|-o in
^ 3.01-< =*= 2.0
6 o -• 1.0
0.0 6.5 9.0 9.5
eVr
• •
10.0 10.5
F I G . 3 . ( B A )
43
On the basis of stability constant the metal ions
may be arranged in the decreasing order Yb > Tb > Dy > Ho >
Eu > Sm > Er > Gd > Nd > Pr > Ce > La BA Complexes -
DBA Lu > Yb > Eu > Er > Ho > Sm > Nd > Dy>
Pr > Tb > Gd 7 Ce > La
TEA Lu > Yb > Er > Eu •> Ho > Dy > Sm > Nd >
Pr > Tb > Gd > Ce > La
CHAPTER - IV
CHARACTERIZATION AND TOXICITY OF LANTHANIDE
COMPLEXES WITH NITROGEN AND SULPHUR CONTAINING
SCHIFF BASES.
14
CHARACTERIZATION AND TOXICITY OF LANTHANIDE COMPLEXEb WITH
NITROGEN AND SULPHUR CONTAINING SCHIFF BASES. _ — •
Experimental
Materials and Methods;
Rare earth chlorides (reagent grade or May and Baker),
NaOH and NaClO,(Riedel);salicylaldehyde, thiophene, 2-
aldehyde and HCIO, (E.Merck); sulphainethoxazole(Roche) were
used as obtained. The IR spectra(600-4000 cm ) were run on
Beckman IR 20, The NMR spectra were recorded on a Varian A-60D
instrument in deuterated DMSO. The conductivity measurements
were made on an Elico conductivity bridge, type CM.82T. The
molecular weights were determined by the viscosity measurement
method in IMF using an Ostwald viscometer. The pH-metric
titrations were performed on an Elico pH-meter, model LI-10T.
All the calculations were made on a model VAX/lI-780 computer.
The estimation of sulphur was carried out by the usual
gravimetric method, while the metals were estimated by EDTA
titration using bromopyrogallcl red and Eriochrome Black-T
as indicators.
Synthesis of the Schiff Bases
Sulphamethoxazole(lO mmol, 2.22g) dissolved in
ethanol was mixed with salicylaldehyde (I)(10 mmol, 1.22 g)
and thiophene-2-aldehyde(lI)(10 mmol, 1.12 g). The resulting
mixture was refluxed on a water bath for 3 to A h to yield
45
coloured crystals or amorphous powders. These were filtered,
washed with ethanol and dried i^ vacuo.
Synthesis of the Complexes;
Ethanolic solutions (30 mmol 1.17 g, 1.1^ g) of the
Schiff bases I and II were mixed with 10 mmol of metal
chloride in the same solvent and stirred for 24 h until an
amorphous solid was obtained. This was kept overnight and
filtered. The complexes were washed with ethanol and dried
In vacuo.
For the determination of equilibrium constants
modified Bjerrum-Calvin pH-metric titration technique was
adopted .
All the solutions were prepared in carbon dioxide
free distilled water. The Schiff bases were dissolved in
the minimum amount of ethanol and 'the volume was made up with
water. Metal halide solutions were prepared in perchloric
acid to prevent hydrolysis.
Toxic Effects
Experiments were carried out on cockroaches
(Periplaneta americana). The concentrations of the Schiff
bases and their complexes were kept within the 6-10 ppm range.
Five insects were taken in each set and were kept under
constant observation. A control set was also run simulta
neously. The percent mortality after 96 h was noted.
4fi
The LD(-Q value was calculated in terms of probit.
Fungitoxicity was also evaluated against Aspergillus
niger and Aspergillus flavus. Aqueous solutions of 2-4% of
the Schiff bases and their complexes were sprayed on a
measured area of fungus colony. The results were compared
against a control set under the same experimental conditions.
The percent inhibition in growth was calculated.
47
Results and Discussion
The complexes were formed according to the reaction
3(C^6"l422°4^4) + WCI3 > (C^gH^3S2 0^N^)3M + 3HC1
^iC^^U^^Nj^S^O^) + MCI3 > (C^^H^^N^S^O^)^^! + 3HC1
The analytical data of the complexes(Table 8) showed the
formation of MLH^.2HpO complexes where M=lanthanide ion and
LH=Schiff base. The molecular weights determined by viscosity
measurements in IMF are close to the theoretical values. The
molar conductances of millimolar solutions of the complexes
in DMF lie in the range for non-electrolytes and suggest that
— 1 2 —1 they are covalent(45-55 ohm cm mol ).
NMR Spectra
The NMR spectra of I and II were recorded in
deuterated IMSO. Singlets observed at &10.26, & 3-33 and
510.50 in the Schiff bases are due to the NH, OCH, and OH
protons, respectively. The proton signal of the OH group in
I and the NH proton signal in the case of II disappear in
the complexes, showing the replacement of a proton by the
metal. The fine splitting of the ring proton persists at
S6.16-7.96 in both the Schiff bases and their complexes.
IR Spectra of Schiff Base I and its Complexes
The IR spectrum of the Schiff base shows a broad
band at 2750 cm due to an intramolecular hydrogen bonded
OH group which disappears on complexation. In such cases the •
-o
d)
CO C Q
tH «H •H ^ O
C O
(1)
o w
+J x; hO
•H
; CO
H =3 O
X3
CO - p C
•H O
Q^
bO C
•H +J rH 01
CD
CO Q
CO
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X a;
rH ft E O
u •H 0)
> . - p
CD TJ C C
< CO
CO I
CD
u CO
D -P O J C (U he rH -H O 0)
CO
2
48
O K> C\J O
\D O 00 CT.
> » - •
ON 00 m o o f ^
00 0> i n r\j
o < r
C T i O O V-
c\i a\
o < r
LfAvD
CO o> m v D
LTAvO
o o o o-
LA r-
^
T3
-P CD
O rH CO o X) a :3 o
en
u
bO
•H +> -P C (U O S O .
u o
vXlvO
o < r
O O
CM K>i
- ; t< r
o o
i n o
< } - < t
O O
c ^ o CM f A
< f < t
O O
o t n CM CM
<(--cf
CM l A L A l A
^~ ^
O K>
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l A a\ 00 CO
V - T—
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< r <j-
0 - 4 -o o C\J CM
o - d -o o
< r< r
o ^
CM CM
00 CM CT\0
r A - d -
covo CM f A
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l A v D
t A t A N.^'
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-d- l A
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t A t A s ^
lACM 00 ON
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r A f A ^- '
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CM CM
O l A
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r A f A x«^
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CM CM
o < r rAr<^,
CM CM
rAK - \ V—^
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CM CM
r A C ^ CM CM
CM CM r— ^ -
CMMD
r A r A ^-^
rACO
CM CM
l A t > -CM CM
CM CM r— r—
CM l A
f A rA ^-^
o o
CM CM
O l A CM CM
CM CM T— T—
o < r
rA rA ^ ^
O f A o o CM CM
X3 CO
en
l A — CM
^-^ -d-
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PC CM
to ^
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r A T ~
DC VD T—
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X CM
TJ 2
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<r 2
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- d o
hA
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cr^o^ O v - O v - o ^ •<-•<- c\jKN r<~\r<> r<>r<-\ r<><r [v_ [.^ rorov KA K> toifoy rovK>i foro K>r<^ r^vfo, rovro
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o m c\j h- •s-in o -^ moo CM o- moo o<r o-v-^n^n CT^CTI o^o^ cr»(T> coco vo>X) mm mm <}-m m m r-T- T- r- T - T - r - r - r - ^ r - v - ^ ^ r- T -C\J OJ CMCVJ CM CM CM CM CM CM CM CM CM CM CM CM CM CM
-4-<t-
mcr>
(\J CM
CM 0 0
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CT>CM
mvo CM CM
m m 04 CM
o<r mm CM CM
CO CM
-J m CM CM
^f^^<-^
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mm
CM m cr><t mm mm
CM-J-
<t-<r mm
t N O m < j -
mm mm mm
mco m^m mm
mcc mm mm
CM m m~3-
00 00
mm
moo mm 00 00
mm
CM m mm coco mm
T- m CM CM
00 00
m m
moo coco ( N O mm
o m
mm
CMVX)
mm
m o mvn
mm
CU
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m o
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2 CM r—
X, <t T—
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CU CO CO
X)
VH VH •H Xi o CO
o CM CM
O CM
rc CM •
CO - 4
m m
o m CO -:t
Z
T—
a: <j-r—
O
o m CM
o CM
as CM •
CD O m m
o m CO <t
2
T—
K -4-T—
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m m CM
o CM
X CM
• U a, m m
o m CO
< } •
2
<r— X.
<f T -
o
o <r CM
o CM
x CM •
13 2
mi
m O
m CO - ^
2
T—
DC -J-—
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m m CM
O CM
a: CM •
n o
m m
o m CO
<r 2 :
X—
X -d-T—
c_>
<t •4-CM
O CM
K CM
« > ,
Q
m m O mi
CO
<r 2
— •X.
<t If—
u
m <r CM
O CM
X CM
• O X
m\
m o
m CO
<r 2
X—
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o
m <r CM
o CM
X CM
• ^ 1
w m m
o m CO
<r 2
^^ X <r V -
CJ
43
50
- (C-0) mode appearinr at 1280 cm is insensitive to
coordination. Our observations are consistent with those of
Kulkarni et al''° Table-9 .
A strong band in the range 1625-1535 cm , assigned
to the azomethine group(H-C=N), has been observed to be
positively shifted after complexation(Table 9 ) . TheT^(NH)
mode at 3150 cm does not appear to be involved in coordina
tion as its position remains unaltered. The sulphur atom
has been found to be inactive as the characteristic band
remains lonchanged. The-S> (C-C), "P (C-N) and ring vibrations
at 1095, 1170 and 1560 cm , respectively, also appear in
the same region of the spectrum for the Schiff base and the
complexes. Some new bands of medium intensity at 3^00(^(0H))
and 1600 cm~ ( S(H-OH)), together with a very wide band at
1140 cm"\ 880 cm"^ and 600-620 cm"'' in the spectra of the
complexes of the Schiff bases have been reported to be due
to coordinated water. These observations are in agreement
l6 with those reported earlier
It is ascertained that the Schiff base coordinates
through the azomethine nitrogen and the phenolic oxygen; the
presence of two molecules of water renders the metal to be
eight-coordinated.
IR Spectra of Schiff Base II and its Complexes
A strong band at 3150 cm in the spectrum of the
Schiff base is assigned to -D(N-H) Table-9 which disappears
51
?
X)
C o o
2; II
0 1
K
to ^^ in C\J ^
CO
0 <r VO
LTv <!• <X)
0 <f ^
0 <r vD
0 <r vO
in <f vO
0 ^ vO
lA
<r \D
in ( \ j
^
to
in
in
o
7*
3: I
7
o in
CM
CO
O CO o
w to to CO to to to to CO
in 00 0 m
0 CD 0 fn
0 CO 0 m
0 00 0 «>
0 CO 0 m
in CO 0 m
0 00 0 m
0 CO 0 m
0 ro 0 K>
^ ^ s
<r z <r 0 C\J
CO -J-—
x MD T ~
0
, — N
M
<U CO CO
XI
v <H • H
x: 0
en
0 fN
X CM
t
CO H J
rn <r
2 <r 0 C\i
rX) K\ r—
X. VD r—
0
0 ( N
X ( N
• QJ 0
K>
-d" 2
-d-0
C\J CO
hn T—
X. VD V -
0
0 CN
X CM
• {-,
a, rn <r
2 <r 0 C\i
CO
^^ V -
X VD r -
0
0 CM
X CM
« T3 2
t n
-a-2
< } •
0 C\]
CO m —
tc VD T—
0
0 r j
I CM
• T3 C5
tn
<J-2
-3-0
CM CO m —
X VD — U
0 CM
X <N
• >> P
m -3-
2 <r 0 CM
CO m T—
X VD r -
0
0 CM
X CM
• 0 DC
K>i
o-2 <r 0 CM
CO fn T -
X VD ^
a
0 CM
X CM
• u w
hr\
•^ 2 <)-
0 00
CO rn T ~
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0
m 0
fn CO <(•
2 CM T—
X <t X—
u
,—\ M M
0) CO CC
X3
«H t H • H
x: 0 CO
0 CM
X CM
• CO
H J
m —
K> 0
m CO -d-
2 r— T—
rc <r X—
0
52
2 II
o 1
X. v-x
CO ^^ o •J-vO
• ITN C\) VO
W v . ^ o <r v£)
• i n <\j vD
en ^.x o <}• vO
• i n C\J vD
w -
O <f vD
• i n C\J VD
M >- i n
<r vD
« i n CM vD
CO v_^ o <r v£)
• i n CM vo
w N « ^
i n <J-KD
« i n CM VD
?
I
o 7
I
7
dj 3 C •H +J c o o c
I 0)
rH X)
CD
o r I CM
• 0) u
m / ^
m o
tn en
cr z
x~ X. <t T -
o
o <N X CM
• u a. rn
^ • ^
m o
rn CO <r
s ^
X <r T—
o
o CO X r j
« n s: m — tn
O rn
CO <r
z T—
a: <f T "
t_)
O (NJ
r. CN •
13 O
rn - m
o fn
CO <r
s T -
K <r r—
O
o CM X CNJ «
>, Q
fn ^^
fn O
K\ CO <t
2 ^—
X -d-r—
CJ
o CM X CM
t
o X
m • ' - ^
m o
m CO
<r 2
^ K
<r T—
o
o CM X CM
• JH
w hn ^ • ^
tn o
m CO <t
z ^
X <t —
o
53
in the complexes, inferring; the replacement of an amino
hydrogen by a metal atom. The complexes show one more band
in addition to a single azomethine absorption band in the
Schiff base at 1525 cm . The other frequencies are
insignificant and occupy the same positions in the free and
chelated ligand.
On the basis of IR studies it is found that the
coordination occurs through the azomethine nitrogen and the
amino nitrogen atom together with two molecules of water,
rendering the metal eight-coordinated.
Electronic Spectra
The electronic spectra were recorded in DMF. The
sharp lines due to an f-f transition originating within the
4f^ configuration of the lanthanide(IIl) ions are affected
by the ligands on complexation. The shift of the absorption
band to a lower wave nuniber(nephelauxetic effect), denoted by (1- B ) ,
is usually of the order of a few percent. A general red
shift of the f-f transition would be observed for these
104 complexes with respect to the corresponding aquo ions
The ^ values below one reflect the covalent nature of the
bond between the metal and the Iigand(Table 10). The value
of the i id(ITl) complexes is higher than that for the Pr(IIl)
complexes, indicatinr the nepheiauxetic effect is more
pronounced at the be' lnninr of the ' f group than with later
numbers. I'he positive vaiu.n- of the bonding parameter, b* and
54
Sinha's covalency parameter also support the covalent bonding.
The bands of the electronic spectra alongwith their
assignments are given in Table 10. These absorption spectra
of rare earth metal complexes arise from electronic transiti-
105 ens within the hf levels ' . The absorption bands of
Pr(lll), Nd(lII), Ho(IIl) and Er(lll) in the visible region
appear due to transitions from the ground levels H,, ^q/pj
IQ and I c/p respectively to the excited J level of the 4f
configuration.
Proton - Ligand Stability Constant
The proton-ligand formation numbers n. for the Schiff
bases I and II were calculated using the Irving and Rossotti
equation. The proton-ligand stability constants(pK ) were
obtained by the pointwise calculation method. The acid
ligand curves in all cases deviated from the pure acid curve
at pH=2.5. The highest n. values obtained were 0.91 and 0.9^
for I and II, respectively, showing the presence of only one
dissociable proton, although the Schiff base I contains two
protons.
Metal - Ligand Stability Constants
In order to prevent polymerization, very dilute
solutions were used. The raetal-ligand titration curves
deviate from the pure ligand curve at pH=2.5-3.5. The
maximum n values in most of the curves are below unity and
0) 0) CO
CQ
V H
V H
•-H x; o
CO
«H O
w (U X <u H (X e o o
+
U
w -o c CD
+ O
+
2
+
a,
o
CO - p CD
Q
iH
CD
o CO
o
o ^( -p o 0
w
o I
0)
CD
C CO
M
>
CO
cu
bO-H JH CO 0 ^ c •
-*>» ^
^
I
CO CU X OJ
s o
K-\
CO (U X Q) t-f ft E O O
CU to CD
Xi
<H
•H
o CO
X
i n
(7>
'N
i n
tn
o
c^ c\j — o «
o
o X CA
C cm
rn
O Cvl
CO
m
cJ~
CO M
i n
Y i n
u. -4-
-4-X
m
>'' C\J
Q r-
CM
cn M
<r
^r CM
" • ^
i n CD
<r
CM
i n V -
f — 1
-d-
>K CNJ
> m en
<t
55
IS o o o
• o
o
' ^ <r
o CM
CO rn
U
i n
i n
o o o fr\
• r-
O o 00 o
• o
o t^ CB o>
o o c o • o
t>-co T—
o • o
rn 0> CTN <T>
o o o o • rn
c T ~
oo -• o
o o c cr^ o
U3 o> CM O
o
CO ^ ' 'J O X
CM 0)
o m
' ^
o CM
C/7 rn
r-O
ft B O U n I—t
CU CO CO
^
«H •H -C
o CO
CTi
o CN
X CM
a.
o rn
CO <r
2
o
CM
o CN
CN
2
m m
o CO
2
i n
o o «• o • CM
O
o o — •
o o o OD
cn
o <r o -J-
• o o •J-<r o • o o o C3 0^
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o CM C^
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a^ o
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o
56
hence only log K. WRS obtained(Table 11) using the equation
log K = pL + log ^ _" -
This infers the formation of a 1:1 complex. The
free ligand exponent pL values were calculated at various n
values and the metal-ligand formation curves were constructed
by plotting n against pL values, yielding the values of the
formation constant log K (Table 11), It has been observed
that log K is inversely proportional to temperature. The
values for free energy(-AG) were also calculated using the
equation(Table 11)
-AG = RT in K
A plot of log K versus e /r shows a roughly linear
relationship, suggesting an ionic character for the metal-
ligand bond while the solid complexes appear to be covalent.
Toxic Effects
The ability of the Schiff bases I and II to exhibit
insecticidal activity is shown in Table 12 and a comparative
study is made with their complexes. It is evident from
Table 12 that the toxicity of the Schiff bases is significantly
enhanced when complexed Fig.4,5
The antifungal activities of the Schiff bases and
their complexes were evaluated against A flavus and A. niger
in the 2-h% concentration range. It is demonstrated from
percent inhibition data that the Schiff base complexes of
II are more toxic than those of I (Table 12).
51
Tabl9-11 Metal-Ligand Stability Constants at 25, 50 and 35 C.
Complexes
( ^ 1 6 " 1 3 " 2 V 4 ^
ic^^H^^s^c^n^)
iC^^H^^S^O^^^]
(C^gH^3S20^N^>
iC^^H^^S^O^N^]
( C l 6 « 1 3 V 4 \ ^
(Cl6"l3VA>
( C 1 6 " 1 3 V 4 \ >
(^^4^11^3303 :
(C,z,H,iN^S303:
( S 4 » 1 1 ^ S 3 0 3 :
( C i 4 " l l V 5 ° 3 ' ( S 4 " l l \ S 3 0 3 :
(S4"llV303:
(S4"llV303;
( ^ 1 4 ^ - 1 1 ^ 3 0 3 :
La
Ce
P r
Nd
Gd
Dy
Ho
Er
La
)Ce
IPr
)Nd
)Gd
)Dy
IHo
)Er
Log K
25°C
3.82+0.11
4.08+0.20
4.22+0.10
4.50+0.17
4.46+0.34
4 .58+0.15
4.67+0.31
4.65+0.14
4.60+0.26
4.94+0.20
5.16+0.26
5.16+0.20
4.90+0.16
5.21+0.20
5.21+0.16
5.21+0.08
0 30°C
3.31+0.20
3.93+0.22
4.07+0.28
4.27^0.19
4.18+0o29
4.29+0.14
4.45+0.15
4.32+0.30
3.94^0.20
4.00+0.15
4.10+0.15
4.36+0.26
4,25+0.16
4.42+0.15
4.60+0.15-.
4 .67+0.15
35°C
3.20+0.40
3.43+0.35
3.63+0.44
4.02+0.17
3.91+0.55
4.10+0.21
4.13+0.29
4.13+0.19
3.39+0.10
3.82+0.20
4,07+0.26
4.14+0.16
3.96+0.26
4.16+0.26
4.20+0.16
4.40+0.16
-A G 25°C
5.19
5.54
5.73
6,06
6.11
6.22
6.34
6.31
6.25
6.71
7.02
7.02
7.09
7.09
7.09
7.09
,K Cal
30°C
4:57
5.42
5.62
5.89
5.77
5.92
6.14
5.96
5.45
5.53
5.67
5.93
6.00
6.00
6.35
6.45
mol-^}
35°C
4.49
4 .83
5.10
5.49
5.10
5.65
5.80
5.80
4.60
5.20
5.72
5.80
5.85
5.85
5.91
6.18
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-4- 0-^<-D CO o < r T-^ O CM-d-m o LPioo • • • • 1 -3" m m m •^"^ v . " - ^ ^ - v ^ " ^ <!- < r O < ! • ' X l 00 00 o - d - ^ m>o o CM <r ^ m o mco • • • • • -4" <f m m t n
K\o • m o
r o ^ ^ O O O mro f - - cD ^ ^ ^ •^^^>v--v. O f < ^ 0 O O CM rovmc^CD
c^<f o m o c^co cr^a^o • e • • •
cvi ovj CM CM r<>
X CU
r H ft E O
U
y ^ ^
-3 -
o <r
2 CM
CO
<r — D: ^ x~-
O s « ^
,_- u
<J-
• O-
C^ m-ct UD KO f<y-:t T-
<r mcM<r oov j mco 1
• • • • -J- m v m m " - " » » ^ ~ ^ ^ " ^ ^ ^ ^ — V
<t o Kxrv£) C 0 v £ ) r<><l- T -UD -cl" m C\j -3-m c^ CM mvco • • • • • -ct -J- m m i m
O <!• O
• \ o o o o l ^ ' v D t ^ C O ^
• ^ ^ * ^ * ' N . ' N » t<^0 O O O f o , < } - v O C^OO
c^<r o m o t^CO CTvCTvO • • • • •
CM CM CM CM KA
X CU
rH ft E O
O
^^ r<
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W
<r 2
CM r—
P: - J -
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58
59
Schiff base I
3 0
— X -
i* 0
^x-
5 0 6 0
T
7 0
Probl ts
Fig. A Probi t ki l l curve for Cockroach
60
30 40 60 50
Probits
Fig.5. Probit kill curve for Cockroach
CHAPTER - V
mYSICOCHEMICAL AND PESTICIDAL STUDIES OF
LANTHANIDE COMPLEXES WITH SCHIFF BASES
DERIVED FROM ALDEHYDE AND DITHIOCARBAMATE
DERIVATIVES.
fil
PHYSICOCHr.FICAL ANL PILSTJCIDAL STULIES OF L >;THANID£
COMPLEXES WITH SCHIFF BASES DERIVED FROM ALDEHYDE AND
DITHIOCARBAMATE DERIVATIVES
EXPERIMENTAL
The rare earth salts(May and Baker), NaOH, NaClO^
(Riedel), HCIO,, Benzoyl chloride, 4-N,N-dimethyl amino
benzaldehyde(E.Merck), sulphanilamide(Wilson), CS^CBDH)
and Thiophene 2-aldehyde (Koch light) were used as such.
Sulphur and chlorine were estimated gravimetrically as
barium sulphate and silver chloride respectively. The IR
spectra(200-4000 cm ) were recorded on 621 Perkin Elmer
spectrophotometer as KBr disc and nujol mull. The NMR
spectra were recorded on a varian A-60D instrument in
deuterated EMSO and UV/Visible spectra were recorded on a
Pye Unicam PU-8800 spectrophotometer. The conductivity
measurements were made on an Elico conductivity bridge
type CM-82T. pH-metric titrations were done on an Elico
pH-meter model L^-10T. All the calculations were done on
a computer model VAX/11-780.
Synthesis of Schiff bases;
The sodium salt of sulphanilamide dithiocarbamate
was prepared by treating etbanolic solution of sulphanil-
imide(3.44 g. ) with CSpC1.526e)and adding under vigorous
SCHEME
6?.
H2N—<^ y — SO2 — NH2 * CS2 + NaOH
H,N-V/ ^ SO. N I H
S +
C ' ^ e Na + H2O
coci
\
ULc=N^^^ H
S O 2 - N — C
H S^CO
® ^ ^ ^
CH
CH3
H I C = N // W S O 9 -
> ' ^ ^ ^ ^
N—C I H
S
S^CO
® ' ^ ^
63
stirring a concentrated aqueous sodium hydroxide(0.80 g)
solution. A yellow product appeared when the mixture was
cooled to about 15°C. The solid was dissolved in 40%
ethanol and benzoyl chloride(2.8 g;.) was slowly added with
constant stirring which yielded S-benzoyl sulphanilamide
dithiocarbamate. It was dissolved in 100 ml ethanol in a
round bottom flask. To this solution was added thiophene
2-aldehyde(2.24 g )(A) or 4-N,N-diraethyl aminobenzaldehyde
(2.80 gm) (B). The resulting mixture was refluxed on
waterbath for two hours. On cooling to about 15 C the
Schiff base crystallized out. It was filtered, washed and
dried in vacuo.
Synthesis of complexes
A mixture of methanolic solution of rare earth
chloride and Schiff base (A,B) in 1:2(M:L) ratio was stirred
for 24 hrs. It was kept overnight in a refrigerator to
yield an amorphous powder. It was washed with alcohol and
dried in vacuo.
For determination of stability constants pH-metric
titration technique was employed. All solutions were
prepared in carbondioxide free double distilled water. In
order to prevent the hydrolysis of the M(III) chloride
dilute solution was prepared in HCIO,. The experiments were
carried out at 25°C, 30°C, 35°C and 0.1M ionic strength.
64
Toxicity studies
Equal number of cockroaches were taken in five
cages and acclamatised. They were allowed to feed on
Schiff bases mixed in a palatable base in different
concentrations ranging from 5-9 ppm (W/W). A control set
was also run simultaneously and test insects were kept
under observation. The % mortality was recorded after
96 hrs. The LD^Q was calculated in terms of probit. To
investigate the fungitoxicity two separate sets of
experiments were done on A. flavus, A. niger along with a
control set. A 2-k% solution of the Schiff bases and
their complexes were sprayed on a measured area of fungus
colony. The results were compared against a control set
under the same experimental conditions.
65
RESULTS AND DISCUSSION
The NMR spectra were recorded in deu1;erated DKSO.
A singlet at 9.^ and ^10.26 in the Schiff bases is due
to CH and NH protons, respectively. The NH proton signal
disappears in the case of complexes indicating the substi
tution of hydrogen by metal. A fine splitting of ring
protons occurs both in the Schiff bases and their complexes
in the range of<S6.8 - 8,0.
A single crystal of the complexes could not be
obtained due to their insolubility although some of them
are sparingly soluble in methanol and nitrobenzene. IR
spectra of Schiff bases exhibit two characteristic bands in
the region 1615-1635 and 3300-3400 cm"\ attributed to-9(C=N)
and'^(N-H), respectively. In the present case a strong band
appears in 1615-1665 cm region assigned to^(C=N) of
azomethlne- coupled with carbonyl group Table-14 . The
unaltered position of^HCN and "> CO even after metallation
infers to the non involvement of this group in coordination.
The complexes are formed by substitution of amino hydrogen
by metal and, therefore, -0 NH also disappears. However, no
distinction may be made between-0 C-N and' ^ C=N as they fall
in the same region of the spectrum. The "5 C=S and C-S may
be identified as they are separated by over 300 cm . The
former band appearing exactly at 1060 cm" undergoes a
negative shift of 30-40 cm after coordination while the
66
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69
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m CO
m S o CM
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2M eg
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CM ^ - N
CM CD
m CO
m ss o CM
:c m CM
CJ v«x
0 X
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r-i
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CM O
m CO
m 2
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X m CM
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CM O
f n CO
m 2
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X m CM
u v ^ XI >-
70
latter remains unaffected Table-1A .
A broad and weak band at 3^00 cm and a sharp band
at 1600 cm~ are assigned tcVOH and SOH, respectively. In
addition, these are followed by weak bands at 1140, 880 and
500-620 cm . These are also due essentially to coordinated 16
water molecules (Table-14).
The electronic spectra of the complexes recorded in
methanol showed absorptions largely in the UV region. The
spectra of only Pr , Nd , Ho and Er complexes were
recorded because they absorb in the visible region(Table-15).
The sharp f-f bands are shifted red with respect to aquo ions.
104 105 These red shifts have been ascribed to nephelauxetic effect '
and result from the changes in the interelectronic repulsion
parameters. The nephelauxetic effect found to be below unity
indicates covalent nature for th^ M-L bond. This is further
104 supported by Sinha covalency parameter and bonding parameters
and b*. The absorption bands of Pr(lll), Nd(lll), Ho(lII) and
Er(III) in the visible region are due to the transition from
the ground level ^H^, IQ/2' S '" 15/2 ^° ^^ excited J
level of 4f configuration, respectively.
Magnetic moment of the complexes has been calculated
10'7 Table-13 by Evans method using the expression
^eff - 0-0618 ( - S ^ )*
CQ
06
CO 0) X OJ
rH p. e o o
w -a
o
•o 2
cu u o
CO 4-> CD
Q . - t CO
o
p. en o c o t^ -p o cu
rH
w
in
I a;
CO E-t
^
PQ
0) CO
CO
VH
<H •H
o CO
0) > 0)
5
Hcv 43
CQ.
CU
> 0)
o
00 O
00
o o
CM Q-
in c^
\o
o
o
CO
o o
<
cu to CO
Xi
=H tH •H
x: 0 CO
^ fct;
>. bO tn QJ C
w
M
0 C\J
• r -
0 l A C\J
• 0
00 00 CTi
• 0
CM T—
0
• 0
0 0
0
r o
C\J
— • 0
[>-ON
• 0
ON CM 0
• c\j cvi 0 • ^ " *
ON cr> 00
•<A
o •
• ^
CM ON 0
• 0
00 ON
• 0
t~-r -0
i \ i < L i n
ITN
4^ NJ "v" 4' ^ CM CM
c^ ON in
<t <t in
i n c~~-- : t 00 CM C ^
m
o CM
CM
O in
in
<3-
ON
CM O
CM O
C\J
<J- ON ON 3 : M M h
KN -d- <f -J-
CM
ON
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M in
CM CM "^J
M
T3
2
I—I
O X,
m CO
in
0 v£)
0
0
i n 0
• 0
CT> ON
tn 0
r—
CM ON
0 •
0
CM 00 ON
o tM
in
4 ' ^ N K N^ Np NK
0
• 0 CM
0 CJN
• 0 CM
ON
0
i n «
C7N
-4-
0
• CM
i n
in
0 i n
• i n
CO
i n •
M
u w
71
72
where f = oscillator frequency expressed in MHZ
T = absolute temperature
M = molarity of the solution
Af = difference in frequency between two signals.
The observed magnetic moment for these ions, at room
temperature, are quite comparable with those of an
octahedral lanthanide ion indicating that the Af
electrons do not participate in bond formation. This is
due to the effective shielding of 4f electrons from external
forces. The following structure has been proposed for the
complexes.
N
N S S N
The metal may attain an octahedral geometry through
chlorine bridging leading to the formation of a dimer. It
seems fairly reasonable because chlorine orbital may overlap
with the vacant metal orbital which synergises the M-L bond.
73
The proton ligand formation number, nA for the Schiff QQ
bases were calculated using Irving and Rossoti Method ^ .
The proton ligand stability constant, pK were obtained by
pointwise calculation. The acid ligand curves deviated from
the pure acid curve in all cases at pH=2.!?. The highest nA
values were obtained at 0.91 and 0.9A for A and B, respect
ively showing the presence of only one dissociable proton.
The deviation of the metal ligand titration curve
commences at pH=2,5 - 3.0. The maximum n values in all
cases were below unity and hence only log K^ were obtained
showing the formation of only 1:1 complex (Table 16). The
metal ligand formation curves were constructed by plotting
n against pL.Log K was obtained by pointwise calculation
using the equation-
Log K = PL + log (n/1-n)
It has been observed that log K is inversely proportional
to temperature.
It is concluded that the solid complexes are formed
in 1:2 ratio having an octahedral geometry while in solution
they have 1:1 ratio where presumably the octahedral
stereochemistry is maintained by the association of solvent
molecules.
The toxicity of the compounds was determined against
several sets of insects and fungi. The percent mortality
m
CD
VH
•H
o CO
«H
o w 0) X 0) H P, e o o
(0
u
I
u o
U o o
o o in
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of the insects was plotted against concentration of the
compounds in ppm(w/w) which gave a sigmoid curve. The data
pertaining to percent kill were transformed into probit,
A plot of probit against log concentration X 100 yielded LDc^
(Table 17 Fig.6,7). It has been observed that the Schiff
base is less effective as an insecticide than their metal
derivatives. In the case of the fungi the area of the fungus
colony in the control and the treated set was measured after
96 hrs and % inhibition in growth of the fungi was calculated
(Table-17). All the compounds tested against fungi appeared
to be growth inhibitor precluding the formation of spores
and further development of fungus colony.
76
Table 17 - % Mortality and LD^Q of cockroaches with a corresponding
concentration of the Schiff bases and its complexes.
Ligand/Complex
Schiff base(A)/
Complexes
Schiff base(B)/
Complex
A. flavus
Log cone. in ppmXIOO
2.69
2.77
2.8A
2.90
-2.95
2.69
2.77
2.84
2.90
2.95
Schiff base(A)/Complex
Schiff base(B)/Coraplex
A. niger
Schiff base(A)/Complex
Schiff base(B)/Complex
% Mortality ligand/ complex
33/40
50/60
70/70
80/80
100/100
20/33
33/40
50/60
70/70
80/80
Probit value
4.6684/4.7467
5.0000/5.2533
5.5244/5.5244
5.8416/5.8416
-
4.1584/4.5684
4.5684/4.7467
5.000/5.2533 5.5244/5.5244
5.8416/5.8416
% Inhibition Data
LD^Q in ppm
ligand/ complex
5.88/5.37
6.91/6.38
Concentration % Inhibition
2.0
3.0
4.0
2.0
3.0
4.0
2.0
3.0
4.0
2.0
3.0
4.0
70/75
75/80
80/84
75/80
80/85
85/90
70/80
75/80
80/85
75/80
80/90
85/95
10
A (Shif f base)
7/
o o
X
£ Q. ex. c c o
c o c o o C7> O
50
Probits
Fig. 6. Probit kill curve for Cockroach
n
B(Shiff base)
o o
6
c o
m c &> o c o o en o
50
Probits
Fig.7. Probit kill curve for Cockroach
CHAPTER - VI
SYNTHESIS CHARACTERIZATION AND TOXICITY OF
LANTHANIDE COMPLEXES WITH SCHIFF BASES -
DERIVED FROM S. BENZOYL DITHIOCARBAZATE AND
ALDEHYDE.
79
SYNTHESIS CHARACTERIZATION AND TOXICITY OF LANTHANIDE
COMPLEXES WITH SCHIFF BASES DERIVED FROM S. BENZOYL
DITHIOCARBAZATE AND ALDEHYDE.
EXPERIMENTAL
Materials and methods;
The rare earth chloride (May and Baker), NaOH, KOH
and NaClO^(Riedel), HC10^(E.Merck), hydrazine hydrate
(Fluka AG ), Carbon dlsulphlde(A.R.), 0.hydroxy benzaldehyde,
thlophene 2-aldehyde, N,N'-dimethyl amino benzaldehyde(B.D,H.)
were used as such.
Sulphur was estimated gravlmetrlcally as barium
sulphate. The l.r. spectra were recorded on Perkln Elmer 621
spectrophotometer as KBr disc and UV/Vls spectra were recorded
on Pye unlearn PU 8800 spectrophotometer. Conductivity
measurements were done on an Ellco conductivity bridge type
CM-82T in nitrobenzene. The pH metric titration was done on
Elico pH-meter model LI-10T(accuracy+^ .05 pH unit) using a
glass calomel electrode assembly in an inert atmosphere. All
the calculations were done on a computer model VAX/11-780.
Synthesis of the llgand;
S. benzoyl dlthiocarbazate was synthesized by the
already
were prepared.
84 method already reported and subsequently their Schiff bases
8«
Typical synthesis of Schiff base;
To 0.02 mole of dlthiocarbazate in 100 ml ethanol was
added 0.02 mol of aldehyde viz. 0-hydroxy benzaldehyde, N,N'-
dimethylaminobenzaldehyde, thlophene 2- aldehyde in a 250 ml
flask. The resulting mixture was refluxed on a water bath for
30 minutes. It crystallised soon after standing at room
temperature. It was washed with ethanol and recrystallized
from benzene.
Synthesis of the complexes M(L),.(HpO)p.
The typical method of synthesis is detailed below.
A mixture of methanolic solution of rare earth chloride
and ligands viz.(S.benzoyl.N-(N-0 hydroxy benzaldehyde) dithio-
carbazate(Ll) S.benzoyl N-(N,N-dimethylaminobenzaldehyde) di-
thiocarbazate(Lp) N-(N-thiophene 2-aldehyde) dithiocarbazate(L,)
in 1:3(M:L) ratio was stirred for 24 hrs and kept at 10-15°C for
12 hrs. It yielded an amorphous powder which was washed with
alcohol and dried in a vacuo.
The stability constants were determined at three
different temperatures (25, 30, 35°C).
Toxicity Studies
To investigate the toxicity of the compounds,
experiments were done on cockroaches (Periplaneta americana).
Five different sets of experiments in varying concentrations
of the compounds ranging from 5-9 ppm were carried out.
81
The number of individuals in each case were kept constant.
A control set was also run simultaneously and the percent
mortality recorded after 96 hrs.
To evaluate the fungitoxicity, fungi were inoculated
and grown in presterilised petridishes of known dimension.
One to two percent solution of the compound was then
sprayed on the fungus colony and observation was made after
96 hrs. A comparison of the treated set was made with that
of untreated. From the area of the fungus colony the per
cent inhibition in growth was evaluated.
?>2
RESULTS AND DISCUSSION
NMR spectra;
The NMR spectra of the Schiff bases were scanned in
deuterated TMSO. It exhibits singlet of -CH=N at 9.3 and
CH, singlet at 53*1 ppm. The singlet due to the ring protons
and the benzoyl ring proton appear in S6.7 -S8«2 ppm and
S7.5 -S8.0 ppm, respectively. The down field shift of -CH=N
proton signals in Ln(lll) complexes supports coordination
through the nitrogen atom.
The Schiff bases under consideration exist in
tautomeric forms- (C and D)
R-C=N-N-cf' - > R-C=N-N = C " ^ ' ' V C=0 ' V C = 0
R=(Ll) OH
8?.
The thione form tautoraerises to thiol fcrm which is
relatively more stable and dominant. The L behaves as
uninegative tridentate- while L2 and L3 are uninegative
bidentate ligands.
The complexes are formed by substitution of H by
lanthanide ions leading to the formation of HCl in the
solution according to the equation.
MCI, + 3(L-H) > ML^ + 3HC1
The absence of chlorine has been checked by a negative test
in the complexes. The replacement of H is further supported
by the absence of characteristic N-H stretching frequency at
3100 cm in the complexes. The molar conductance of
-1 2 millimolar solution of these complexes (1.0 - 7.20 ohm cm
mole ) in nitrobenzene indicated them to be covalent in
nature (table-18).
The complexes display bands at 3^00 cm and 1600
due to'^(OH) and ,5 OH. In a recent communication Ruano
and coworkers have noted two additional bands at 1150 and _-|
1100 cm for coordinated water molecules. In the present _1
work this has been observed as split band in 1100-1175 cm
range suggesting the presence of bonded water molecules.
Two strong bands at 1715 cm"'', 1050-1060 cm"^ in the IR
spectra of Schiff bases have been assigned to~^(C=0) and
-? (C=S), respectively. The former band remained uneffected
after complexation showing the non involvement of (0=0) group
8S
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while the latter shows a negative shift oi 20-40 cm
suggesting the coordination through sulphur atom. A strong
— 1 band at l520Hh5 cm in the free ligand assigned toV (C=N)
stretching frequency is shifted to lower wave number in the
complexes(Table-19). It is due to the electronic drift from
nitrogen atom to the central metal ion.
Electronic spectra:
The electronic spectra of complexes were run in
methanol. The intraligand transition occcur below 380 n.m.
and have not been discussed. The sharp line due to f~f
transition originating within the configuration of
lanthanide ions are influenced by the ligand after complexa-
tion. A red shift of the f-f transition is observed for the
105 1 CP complexes with reference to the corresponding aquo ions '
Nephelauxetic ratio, has been calculated from the relation.
^ = — - — H '>5comp/-%) aquo " n=1
The covalency parameter, and bonding parameter, b*
have also been calculated from the relation
%S= ( " ) X 100
b^ = ^ ( 1 -/S )i
The positive value of the b* reflects covalent character for
the metal ligand bond. The presence of sulphur atoms
8 a Table 19 - IR spectra of Schiff base complexes ol (L1, L2 and
L3) and their assignment.
•S)NH S) C=S S) C=N
^15^12°2^2^2 ''°° ° *-* '' ^
Schiff base L1)
" 15 11* 2 2 2 3^^ •^^2'^
^15^11°2^2^2^3^®*^"2^
^15"l1°2^2^2^3^^*^"2^
C^^H^^O2N2S2)^Nd.2H2O
^15^11 °2^2^2 3" ^ • "2°
C^5H^^02N2S2)3Dy.2H2C
C^^H^^O2N2S2)5H0.2H2O
^15^11^2^2^2^ 3 ' 2*
^15"l1°2^2^2^3^^*^"2^
C, H^^02N2S2)3LU.2H2C
C^yH^^O N3S2 3100 1050 1615
Schiff base Lp)
C^yH^gO N3S2)3La.2H20 - 1030 1605
C^yH^gO N3S2)3Ce.2H20 - 1020 I6OO
C^yH^gO N3S2)3Pr.2H20 - 1030 I6OO
C yri O N3S2)5Nd.2H20 - 1025 I6OO
Contd,
1020
1020
1020
1030
1030
1025
1030
1020
1030
1025
1030
1030
1602
1610
1600
1602
1610
1600
1600
1610
1600
1610
1610
1610
91' Table 19 - continued
-ONH -S) C = 3 ^ C = N
1050
1025
1020
1025
1030
1025
1020
1025
1600
1600
1610
1605
1600
1600
1602
1600
(C^^H^g^O N^S2)3Sm.2H20
(C^^H^^O N3S2)3Gd.2H20
(C^^H^gO N3S2)3Tb.2H20
(C^^H^gO N3S2)3Dy.2H20
(C^^H^gO N332)3Ho.2H20
(C^^H^gO N3S2)3Er.2H20
(C^^H^gO N3S2)3Yb.2H20
(C^^H^gO N3S2)3Lu.2H20
C^3H^Q0 N2S3 3100 1060 1620
(Schiff base L^)
(C^^HgO N2S3)3La.2H20
(C^3HQ0 N2S3)3Ce.2H20
(C^3H^0 N2S3)3Pr.2H20
(C^gH^O N2S3)3Nd.2H20
(C^3HgO N2S3)33m.2H20
(C^^HgO N2S3)3Gd.2H20
(C^3HgO N2S3)3Tb.2H20
(C-13H5O N2S3)3Dy.2H20
(C. ,Ho0 N' S^)^Ho.2HoO 1 3 9 2 3 3 2
(C^ HQO N2S^)3Er.2H2C
(C^3HgO N2S3)3Yb.2H20 .
(C^3Hg0 N2S3)3Lu.2H20
1020
1030
1025
1020
1030
1030
1025
'.030
1025
1020
1020
1030
1605
1602
1605
1600
1610
1605
1600
1610
1605
1610
1600
1605
91
synergises the covalent nature of the metal ligand bond
which is evident from b* and 1 - values. It is believed
that this is due to the d orbital of sulphur which promotes
the overlap of ligand orbitals with those of metal. The
absorption bands of the compound and free aquo ions in the
present work appear in the same region as reported by
104 105 Sinha ' . The absorption spectra of Lanthanide ions
arise from electronic transition within 4f levels. They
are normally forbidden but are allowed only when the
degeneracy is lifted up in the Af orbitals by external
crystal field. The absorption bands in the visible region
in the case of Pr(IIl), Nd(IIl), Ho(lll), Er(IIl) appear , 5 4 5
due to the transition from ground level ( H. , IQ/2» - R
15/2^ to the excited J levels (Table-20) of 4f configuration.
Magnetic moments:
The magnetic moment(Table-18) of the complexes at •1 I J y
room temperature has been calculated by Evtan method
employing the expression
Agff = 0.0618 i^- . -^ )*
where
f = oscilator frequency expressed in MHZ
T = absolute temperature
M = molarity of the solution
Af = The difference in frequency between the two
reference signals.
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93
The/t ff values dc not deviate substantially from van
Vleck values. The 4f electrons do not take part in the
bond formation probably due to effective shielding from
2 2 external forces by the overlap of 5S , 6p shell. The
magnetic moment for free lanthanide ions are not appreciably
different from the compiex ions. In the present work too,
they are invariably within the range of paramagnetic
lanthanide ions.
Proton ligand stability constants
The deviation of acid ligand curve from the pure
acid curve(at pH 2.5) indicates only the dissociation of
proton while the proton ligand formation nxmber, nA, gives
the total number of dissociable protons. Since the nA value
falls below xrnity it indicates the presence of only one
dissociable proton. The proton ligand stability constants
pK , for L1, L2, L3 are 7.0 - 6.95, 5.58, respectively.
Metal-ligand stability constaiit;
The formation of polynuclear species and the
hydrolysis of the metal was prevented by taking dilute
solution in HCIO/. The metal ligand titration curve deviates
from pure ligand curve at pH=2.5 - 3.0 showing the formation
of only one species (Table-21) in solution.
The rare earth ions have weaker complexing tendency
as compared to transition metal ions owing to their larger
Si
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9?
hydrated radii and non-availability of the orbitals for
covalent bond formation. Since the formation of 1:2/1:3
complex in solution is prevented the metal ion may attain
110 its coordination number by association of solvent molecules
Toxicity:
It is evident from LD^Q (Table 22 fig.8,9,10 ) that
complexes are more toxic than the free Schiff bases. The
magnitude of per cent growth inhibition of fungi by the
complexes is relatively less significant though the order of
the toxicity essentially remains the same (table 23). It is
obvious that metallation enhances the pesticidal activity of
the Schiff bases. It is believed that these Schiff bases
act as contact poison.
96
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Probits
Fig.8. Probit kill curve for Cockroach
1(U
L2 (Ligand )
10
30
L2 (Complex)
40 60 50
Probits
Fig.9. Probit kill curve for Cockroach
in?
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Probits Fig.10. Probit kill curve for Cockroach
CHAPTER - VII
STUDIES ON COMPLEXES OF LANTHANIDE(III)
WITH SUBSTITUTED THIAZOLIDIN-4-ONES.
STUDIES ON COMPLEXES OF LANTH/iNIDb( III) WITH SUBSTITUTED
THIAZOLIDIN 4-ONES.
EXPERIMENTAL
All the chemicals were used as receivedo The IR
spectra(200-4000 cm ) were recorded on Beckman spectro
photometer as KBr disc and nujol mull. The NMR spectra,
in deuterated DMSO was recorded on Perkin Elmer instrument
Varian A60 D, UV/vis spectra were recorded on Pye Unicam
PU 8800 spectrophotometer. The conductivity measurements
were made on Elico conductivity bridge type CM-82T. The
pH-metric titrations were done on Elico pH-meter model
LI-10T Calculations were done on a computer, Digital
VAX-11/780.
Synthesis of the ligands;
Cyclopentanone, methyl propyl ketone, hexyl methyl
ketone, (0,05 mol), mercapto acetic acid(0.l4 mol) and
ammonium carbonate (0.15 mol) dissolved in dry benzene
were refluxed for about sixty hrs. The resulting benzene
solution was washed thrice with water, 1M NaOH and finally
with water. It was dried over anhydrous sodium sulphate.
Benzene was removed through suction when it yielded
crystalline product.
10 SCHEME
( N H 4 ) CO3 >.2NH3 + C O 2 + H 2 O
0 = C - C H 2 S H 1
OH
H - 1 - - ' N - H 2
I - H , 0
0 = C - C H 2 - S H
: N H 2
0 = C - C H 2 - S H /
H2N* , 0 ' \ /
c / \
R R
i O r C - C H o - S l H i
HN jflOH
\ 7-c
/ \ R R ( I ) Cyclopentanc
( l I ) M e t h y l , P r o p y l ( I I l ) H e x y l , M e t h y l
I — H 2O
O r C - C H 2 I I
HN S
\ / C
/ \ R R
Synthesis of the complexes
A typical preparation of the complexes is outlined
below.
Thiazolidin-4-ones(0.03 mol) dissolved in 20 ml of
ethanol was mixed with lanthanide (III) chloride at room
temperature(0.01 mol). The resulting mixture was
continuously stirred and kept overnight at 15°C. An
amorphous solids thus obtained was filtered, washed with
ethanol and dried in vacuo.
Toxicityt
Five sets of experiments were done. The insects
(cockroaches) were fed on the compounds in varying
concentration ranging from 1-5 ppm. Standard method of
evaluation was adopted. Fungitoxicity was also evaluated
98 by agar plate method .
10, .
RESULTS AND DISCUSSION
The thiazolidinones are negatively charged bidentate
ligands. Analytical result suggests the formation of
M(L),.2HpO type complexes (Table 24). The molar conductance
of their millimolar solution in methanol indicated their
— 1 2 —1 covalent nature(40-55 Ohm Cm mole ).
NMR spectra;
The spectra of the complexes scanned in EMSO, d^ have
been compared with those of ligands. The NH proton signals
of the secondary and primary amines are dependent on the
extent of exchange rate. If the rate of exchange is slow
the NH peak broadens and the protons are decoupled from the
nitrogen atom and the CH protons. However, it gives a broad
singlet corresponding to NH proton in §9.0 -§9.1 region
which does not appear in the complexes showing the replace
ment of amino proton. The CHp proton signals in the case
of ligands and their complexes is observed in the range
83.4 -S3.7. Other protons are also observed in the range
So.7 -&3.5.
IR spectra;
The thiazolidin-A-ones under question have apparently
three coordination sites. However, for steric reasons all
the sites may not be prone to coordination. A strong"^(N-H)
band (3150 cm ) in free ligand disappears in the IR spectra
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110
of the complexes showing replacement of aminohydrogen by
metal ions which is further supnorted by a negative test
of chlorine in the complexes.
MCI, + 3LH ) M(L)^ + 3HC1
On passing from free to complexed ligand there is
a small negative shift inS)(C=0) as a consequence of
coordination followed by a decrease in CO double bond
character. The absorption bands observed at 3350-5^00 cm
and 1600 c.rT have been assigned to-OCOH) and8(H-0H)
respectively. In addition, broad bands observed at 1145-
1150 and 800 cm have also been ascribed to coordinated
water molecules. These results are in consonance with 1 fi
those reported earlier supporting the presence of two
molecules of water which render the metal ions eight
coordinated.
_i A weak band at 290 cm in the far IR region of the
complexes has been assigned toS^CM-N). The metal oxygen
frequency occurring at 390 cm in the complexes, indicates
that coordination occurs through carbonyl oxygen and
nitrogen (Table-25).
Electronic spectra
The electronic spectra of the complexes were
recorded in methanol. The intraligand transition occurs
mainly in UV region and hence they have not been discussed.
Only Pr" , Nd" , Ho"*" and Er" ^ have been found to absorb
in the visible region. The nephelauxetic effect ' ^ is
M
111
(\i
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0)
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o I
7
o ON f ^
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O cr> K>
o 0 ^ r<
O cy\ f<-\
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O
a> ro
O 0> K>
o o^ K^ 1
o o o o o CTi CTi Cr> C7^ (T> hr> rTA N-> K ^ h O
M
W <U X
a, s o o m di C o I
<!• I C
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2
9
O 11
O
o
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o ON CM
O Ch C\J
o ON C\J
n ON CM
o <J\ CM
o cr\ CM
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o a^ CM •
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o ON CM
o UN CM
o (J\ CM
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o o t-
lf\ CTv VD
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112
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f V C V C V C V J f V C X J C X J C V O J
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11^
very small showing weak metal-ligand interaction. Normally
the electronic transition of the aquo ion is red shifted
with reference to the complexed ion followed by an increase
in intensity of the transition (Table-26). These results
are consistent with those reported for the lanthanide
104 109 complexes ' . The absorption bands in the visible
region emerge due to the transition from ground levels( H,, 4 5 4 . 4 IQ/^, IQ and I-IK/O) " ^ " ^ excited J levels of f
configuration.
The positive value of bonding parameter y3 , b* and
Sinha ' covalency parameter,S^ refer to covalent
bonding. The spectra of lanthanide ions may be used as
probes of local microsymmetry of the environment of the ion.
The large spin orbit coupling split the free ion terms into
multiplets of given J values; this is due to the local
crystal field and reflect directly symmetry of the compovinds,
Magnetic moment
Magnetic moment of the complexes has been calculated
107 by Evans method based on NMR spectroscopy using the
expression;
>^eff = O-O Q ( - ^ ^ -IT ^^
The observed magnetic moment for these ions are quite
1 Gil comparable with those of octa coordinated lanthanide ions
indicating that Af electrons do not participate in bond
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formation. This is due to effective shielding of 4f
electron from external forces Table-24 ,
Stability constant
The nA value below unity shows the presence of only
99 one dissociable proton in solution - . In order to prevent
polynuc^ear species very dilute solutions of the rare earth
salts were used. The metal ligand formation number, n were
also below xmity and, therefore, only log K was obtained.
It is observed (Table-27) that log K is inversely
proportional to temperature. It is concluded that solid
complexes are formed in 1:3 ratio having octahedral geometry
while in solution they have 1:1 ratio where the octahedral
stereochemistry may be attained by the association of solvent
molecules.
Toxicity:
96 The sulphur compounds have inherent pesticidal
property and hence it seemed essential to investigate their
toxicity against insects and fungi. The insecticidal
activities of thiazolidin-4-ones and their complexes in term
of LDcQ is given in Table-28. On the basis of the mortality
data the thiazolidin-4-ones may be arranged in the ascending
order of their toxicity.
Ill ^ . II < I
All thiazolidin-4-ones and their complexes have been
screened for their antifungal activities. It has been noted
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which is exactly the reverse to those found for insects.
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Fig.n.Probit kill curve for Cockroach
70
10
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I I ( Lagand )
o o X
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Fig.12.Probit kill curve for Cockroach
12
I I I (Ligand)
50
Probits
Fig.13. Probit kill curve for Cockroach
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