1

CHAPTER 1. INTRODUCTION

Complexes of transition metal ions with multidentate organic ligands have

been the subject of intensive research because they not only have interesting

spectral and magnetic properties, but they also possess a diverse spectrum of

biological activities [1-6]. These complexes often possess remarkable and unique

spectroscopic, photophysical and electrochemical properties which may be

exploited in sensory and diagnostic applications and there have been a number of

reviews [7-12] on the utilisation of transition metal complexes as ion and

molecular sensors. Based on the widely diverse coordination environment of the

transition metal complexes, and variation in the identities of the coordinating

ligands, synthesis of such complexes with desired molecular geometry can be

realized. It is well known that several metal chelates have been shown to inhibit

tumor growth [13] and some drugs even exhibit increased activity when

administered as metal complexes [14-16]. Thus, the study of the coordination of

transition metal ions with different types of ligands has been amplified by the

recent developments in the field of bioinorganic chemistry and medicines [17].

The rich diversity of transition metal coordination chemistry, therefore, provides

exciting prospects for the design of novel coordination ligands having unique

structures and valuable functional characteristics [18-24] and significant efforts

directed toward the design of specific architectures formed by the self-assembly

processes have been carried out in a number of fields of synthetic chemistry

[25-27]. In many cases, transition metal ions and their complexes play a central

role in controlling the reactivity and mechanism of the chemical reactions of

2

interest. The unique ability of transition metal ions and their complexes to control

the chemistry of environmental, industrial, and biological processes has increased

the importance of clarifying their mechanistic behavior in simple and complex

chemical processes.

While the knowledge of coordination chemistry is essential to the

understanding of the structural and functional features of various biomolecules

like metalloproteins, its medical application ranges from the development of MRI

contrasting agents, radiopharmaceutical chemotherapeutics to the treatment of

metal toxicity [17]. Studies on the complex formation of metal ions with a number

of biomolecules or biologically active ligands have, in fact, attracted a lot of

interest during the last few years because they act as models for the interactions of

metalloenzymes [28] and other complicated proteins [29] in the biological

systems. Thus, the bioinorganic chemistry of nickel is a topic of increasing

interest [30, 31] because the study of the interactions of Ni(II) with nucleotides

offers an unique opportunity for understanding various properties of Ni(II)

complexes such as the carcinogenicity of some nickel compounds [32] and the

antineoplastic activity recently detected in some nickel complexes [33].

Furthermore, development in the field of bioinorganic chemistry has also led

to an increased interest in complexes of N, O-donor ligands since it has been

recognized that many of these complexes may serve as models for biologically

important species having N and O as bonding sites [28]. Amino acids and their

derivatives are extensively studied as typical N, O-donor ligands. In the

N-protected amino acids, the introduction of a substituent such as acetyl, benzoyl

3

or benzylo carbonyl group directly on the amino group could reduce the ligand

field of the in-plane donor thus diminishing the affinity of the amino group for the

metal ion and permitting a variety of coordinating type. Aroyl hydrazones derived

from amino acids and N-protected amino acids are of special interest in that they

not only possess many potential donor sites but there is also possibility of keto-

enol toutomerism which may lead to varied bonding and stereochemical behavior

in the complexes in which they act as neutral or mononegative or even as

dianionic ligands depending on the aroyl substituents and the reaction conditions

[34, 35]. Their chemistry has also been intensely investigated owing to their

cooperative capability [36, 37], their pharmacological activity [38-40] and their

use in analytical chemistry as metal extracting agents [41]. The interest in the

study of these compounds arose from their tendency to form chelates with

transition metals, lanthanides, and main group metals, and their interactions have

served as model systems for the study of many biomolecules and metalloproteins.

To understand the complexation reactions of metals, complex formation

ability of the ligands and the activities of the complexes formed, it is necessary to

have a detailed knowledge about the thermodynamic and solution equilibria

involved in these reactions. The extent to which a ligand binds to a metal ion is

normally expressed in terms of the stability constants and the information about

the concentration of a metal complex in equilibrium mixture can be predicted on

the basis of their formation constants in solution. Most of the reported studies on

the formation and stability constants of the metal complexes are carried out in

aqueous or mixed aqueous organic solvent media. Although there are reports [42, 43]

4

on the effect of micelles in the reacting systems of many chemical reactions, not

enough attention has been given to understand the role of micelles in the metal

complexation reactions. Since micelles represent a multiphase system where a

species may be distributed in both the bulk aqueous phase and on the micelle’s

surface, study of the metal-ligand complexation reactions in micellar media would

assume a critical significance in view of the fact that reaction behavior observed at

surfactant interfaces are expected to be more representative of many biological

reactions than are reactions studied in dilute aqueous solutions [44].

An extensive literature survey reveals that there are a number of reports on the

synthesis, characterization and physicochemical properties of a number of metal

complexes of various N, O-donor ligands, and mention may be made here of only

the transition metal complexes of N, O-donor Schiff bases and determination of

stability constants of the transition metal complexes. Although an effort has been

made to make an exhaustive survey of the existing literature on the reports on the

study of the various physicochemical constants like stability constant and

thermodynamic parameters, only the abstracts that appeared in the last ten years in

the above fields and relevance to the present work are given below.

Binary and ternary Co(II), Ni(II), Cu(II) and Zn(II) complexes of the type MY

and MXY [X = N-(2-hydroxy-1-naphthylidene)-2,6-diisopropylaniline and Y = N-

(2-hydroxybenzylidene)-2,3-dimethylaniline] had been examined pH-metrically

[45] at 27±0.5oC and 0.1 M ionic strength in 75:25 % (v/v) 1,4-dioxane-water

medium. The values of stability constants for binary and ternary systems were

calculated.

5

Tayade et al [46] synthesized 2-amino-4-hydroxy-6-methylpyrimidine and

1-(4-hydroxy-6-methyl pyrimidino)-3-phenylthiocarbamide and the interactions of

Cu2+

, Cd2+

, Cr2+

ions with both the ligands were studied at 0.1 M ionic strength in

70 % dioxane-water mixture by Bjerrum method [47] as adopted by Calvin and

Wilson [48]. It is observed that these metal ions would form 1:1 and 1:2

complexes. The data obtained were used to estimate and compare the values of

proton-ligand stability constant (pK) and metal-ligand stability constants (log k)

and the effect of substituents were studied from estimated data.

Thermodynamic protonation constants of 5-aldehydosalicylic acid-aniline

Schiff base, and o-, m-, p-Toluidine Schiff bases with 5-aldehydosalicylic acid

were determined [49] by Calvin-Bjerrum pH titration technique [47, 48] as used

by Irving and Rossotti [50]. The thermodynamic formation constants of the

chelates of Cu(II), Co(II), Ni(II), Zn(II), Cd(II) and Mg(II) with these four ligands

were determined at four different temperatures in 50% (v/v)water-ethanol

mixture; the stabilities of complexes follow the Irving-Williams order [51].

Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes were

prepared [52] by template reaction of 5-acetyl 2,4-dihydroxyacetophenone

(H2-ADA) and ethylenediamine in the presence of metal ions and characterized

on the basis of elemental analyses, conductivity, magnetic moments, infrared and

electronic spectral data. The Schiff base was reported to bind to metal ions in

bis-multidentate ONNO mode leading to two dimensional Schiff base polymers.

All the complexes have been assigned octahedral stereochemistry.

6

Complexation of Cu(II) ion with dapsone in solution was studied

spectrophotometrically [53] at absorption maximum of 680 nm at temperatures

250C, 45

0C and 60

0C. The stoichiometry of the complex was determined using

mole ratio and Job’s continuous variation methods. The data showed that Cu(II)

and dapsone combined in 1:1 molar ratio at pH 7.4 with ionic strength maintained

at O.1 M using KNO3. The stability constants were 0.086 x 103, 0.090 x 10

3 and

0.137 x 103, 0.142 x 10

3 at 25

0C and 45

0C, respectively.

The complexation equilibria of L-norvaline (Nva) and ferulic acid (FA) were

studied [54] in aqueous solutions at 298 K and in fixed ionic strength (0.15

mol·dm−3

NaNO3) by means of potentiometry and spectrophotometry techniques.

The complexing capacities of Nva and FA with Fe3+

, Cr3+

and Cu2+

ions and their

overall stability constants in aqueous solutions were obtained by the

HYPERQUAD 2008 program [55] from the potentiometric data. The

concentration distributions of the various complex specia in solution were

evaluated and discussed. The spectroscopic UV−visible measurements were

carried out to give qualitative information about the confirmation of the

complexes formed in these solutions.

The complex formation between a new Schiff base and Ni2+

, Co2+

, Cu2+

, and

Zn2+

ions in ethanol, dimethylformamide (DMF), and acetonitrile (AN) was

studied [56] spectrophotometrically using rank annihilation factor analysis

(RAFA). According to molar ratio data and Job’s plots, the stoichiometry of

complexation between the Schiff base and the cations was 1:2, and that between

the Schiff base and Cu2+

in all solvents and Zn2+

in AN was 1:1. Formation

7

constants of these complexes were derived using RAFA on spectrophotometric

data. The effect of surfactants such as sodium dodecyl sulfate,

cetyltrimethylammonium bromide and Triton X-100 on the complex formation

constant of Cu2+

with the Schiff base in DMF was investigated.

A series of complexes of divalent transition metal ions with malonyl

bis(salicyloylhydrazone) (H4MSH) were prepared and characterized [57] with the

help of conductometric and potentiometric methods. The proton-ligand and metal-

ligand stability constants were obtained pH-metrically. The low molar

conductance values measured at 289 K for these complexes indicated their non-

electrolytic behavior. The elemental analyses of the complexes showed that the

complexes were 1:1 and 2:1 (M:L) stoichiometry with the existence of water,

chloride, acetone molecules inside the coordination sphere as evidence from the

IR spectral studies and UV–visible spectra of the complexes had been discussed.

Patil et al [58] synthesized a series of Co(II), Ni(II) and Cu(II) complexes of

the type ML2 with Schiff bases derived from methylthiosemicarbazone and

5-formyl-6-hydroxy coumarin/8-formyl-7-Hydroxy-4-methylcoumarin. The

complexes were non-electrolytes in nature. Based on the analytical, spectral (IR,

UV–Vis, ESR, FAB-mass and fluorescence), magnetic and thermal studies,

octahedral geometry for all the metal complexes was proposed in which ligand

was coordinated to metal ion through azomethine nitrogen, thione sulphur and

phenolic oxygen atom via deprotonation.

The condensation reaction of succinyldihydrazide with glyoxal in the presence

of divalent metal ions resulted [59] in the formation of the complexes of type

8

[M(C6H8N4O2)X2], [M = Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and X = Cl–, NO�

�,

CH3COO–]. The complexes were characterized based on elemental analyses,

conductivity measurements and electronic, NMR, infrared spectral studies. A six-

coordinated distorted octahedral geometry in which two nitrogen and two

carbonyl oxygen atoms were suitably placed for coordination toward metal ion,

had been proposed for all the complexes.

Cu(II), Ni(II), Co(II), Mn(II) and Fe(II) complexes with an asymmetric

tetradentate Schiff base derived from dehydroacetic acid, 4-methyl-o-

phenylenediamine and salicylic aldehyde were synthesized and characterized

[60] by elemental analysis, conductometry, magnetic susceptibility, UV–Vis, IR,

1H-NMR spectroscopy, powder X-ray diffraction analysis of samples and thermal

analysis, and screened for antimicrobial activity. The ligand behaved as a dibasic

tetradentate ligand towards the central metal ion with an ONNO donor atoms

sequence and formed 1:1 (metal:ligand) complexes. The physico-chemical data

suggested square planar geometry for the Cu(II) and Ni(II) complexes and

octahedral geometry for the Co(II), Mn(II) and Fe(II) complexes. The powder X-

ray diffraction data suggested a monoclinic crystal system for the Co(II), Mn(II)

and Fe(II) complexes.

A new series of homo- and heteropolynuclear Cu(II) complexes of N, N"-

bis[1-biphenyl-2-hydroxyimino-2-(4-acetylanilino)-1-ethylidene]diamines were

prepared and characterized [61] by different physichemical techniques. Homodi-,

homotrinuclear and heterodinuclear Cu(II) perchlorate complexes of tetradentate

Schiff bases which possess N4 donor sets derived from the condensation of

9

4-(arylaminoisonitrosoacetyl)biphenyl and diamine derivatives were synthesized

and characterized. Elemental analyses, stoichiometric and spectroscopic data of

the metal complexes indicated that the metal:ligand ratio of dinuclear Cu(II)

complexes were found to be 2:1 while this ratio was 3:2 in trinuclear Cu(II)

complexes and the metal complexes indicated that the metal ions are coordinated

to the oxime and imine nitrogen atoms. The extraction abilities of the novel

ligands were also evaluated in chloroform by using several transition metal

picrates such as Mn2+

, Co2+

, Ni2+

, Cu2+

, Zn2+

, Pb2+

, Cd2+

, Hg2+

. Both ligands

showed a high affinity to Cu2+

ions.

Potentiometric and spectrophotometric methods were employed to investigate

[62] the complexation reactions of the two novel tripodal ligands, cis,cis-1,3,5-

tris{(2-hydroxybenzilidene)aminomethyl}cyclohexane and cis,cis-1,3,5-tris{[(2-

hydroxyphenyl)ethylidene]aminomethyl}cyclohexane with H+ and Fe(III) at an

ionic strength of 0.1 M KCl and at 25 ± 1°C in aqueous medium. Three

protonation constants each for the ligands were determined and were used as input

data to evaluate the formation constants of the metal complexes. Formation of

metal complexes of the types FeLH3, FeLH2, FeLH, FeL and FeLH−1 were

depicted in solution.

A novel Schiff base was prepared [63] via condensation of 4-aminoantipyrine

and 2-aminobenzoic acid and characterized based on elemental analysis, mass, IR

and 1H NMR spectra. The molar conductance data revealed that all the metal

chelates prepared were non-electrolytes. IR spectra showed that the ligand was

coordinated to the metal ions in a uninegatively tridentate manner with NNO

10

donor sites of the azomethine-N, amino-N and deprotonated carboxylic-O.

Magnetic and solid reflectance spectra suggested that these complexes were

octahedral. The thermal behavior of these chelates showed that the hydrated

complexes lose water molecules of hydration in the first step followed

immediately by decomposition of the anions and ligand molecules in the

subsequent steps.

The formation constants of Cu(II), Ni(II), Co(II) and Mn(II) complexes of

3-[{3-(3’-chloro phenyl}-prop-2-enoyl]-4-hydroxy-6-methyl-2H-chromen-2-one

were studied [64] by using Irving- Rossoti method [50] at 30 ±1°C and 0.1 M dm-3

ionic strength using sodium nitrate as an electrolyte. The factors influencing

formation and stabilities of binary complexes were discussed.

The acid-base equilibria of Schiff bases containing cyclobutane and thiazole

functional groups and their CuII), Ni(II) and Zn(II) complexes were investigated

[65] pontentiometrically in 60 % dioxane-water media at 25.0 ± 1°C and ionic

strength 0.10 mol L-1

NaClO4. The values of the protonation constants determined

in this study, log KOH, log KNH(1) and log KNH(2), were related to the protonation of

the phenolate oxygen atom, the nitrogen atom on the thiazole ring and the imine

nitrogen atom, respectively. The variation of the protonation constants of the

Schiff bases was interpreted on the basis of structural factors. The Schiff bases

form stable complexes with Cu(II), Ni(II) and Zn(II) metal ions. Complex

stabilities follow the trend: Cu(II) > Ni(II) > Zn(II), which is in agreement with

the Irving-Williams series [51].

11

Shaker et al [66] prepared a bidentate Schiff base (L) by condensation of the

p-amino-2,3-dimethyl-1-phenyl-3-pyrozoline-5-on with salicylaldehyde in

methanol. Ethanolic solutions of the Schiff base and 8-hydroxyquinoline (Q)

reacted with aqueous solution of bivalent metal salts to give complexes of the

general formula [M(L)(Q)] where M=Fe, Co, Ni and Cu. The solid products had

been characterized using elemental analyses, magnetic susceptibility,

conductivity, FTIR and UV-Vis spectral data.

Protonation constants of Schiff bases derived from 2-hydroxy-3-methoxy

benzaldehyde and 2-aminopyridine, 2,3-diaminopyridine, 2,6-diaminopyridine, or

3-aminomethylpyridine were determined spectrophotometrically [67] in the 1:4

methanol/water. The effect of Cu(II) ions on absorption and emission spectra of

these ligands was examined in the buffered dioxane/water 1/1 system (pH 5.8).

Strong complexation of Cu(II) and formation of a 1:1 complex were observed for

the bis-Schiff base derived from 2,3-diaminopyridine. Cu(II) complex with the

base with 2-aminopyridine was isolated and characterized by elemental analysis,

magnetic susceptibility measurement, UV–Vis and IR spectrometry.

Synthesis of novel Ni(II) complexes with a new hydrazone derived from

isoniazid had been reported [68]. In the complexes [Ni(L)2X2] or [Ni(L)3](ClO4)2,

where L = N-isonicotinamidofurfuraldimine and X = Cl− or NCS

−, the hydrazone

behaves as neutral bidentate coordinating through the carbonyl oxygen and

azomethine nitrogen. On the basis of elemental analysis, molecular weight

determinations, magnetic susceptibility/moment, thermogravimetric,

12

electrochemical, and spectroscopic studies, the new complexes were characterized

with octahedral geometry.

Cu(II), Co(II), Ni(II), Cr(III), and Fe(III) complexes of a Schiff base derived

from the condensation reaction between leucine and 2-acetylpyridine were

prepared and characterized [69] by elemental analyses, spectral analyses (IR, UV),

thermal analyses (TGA), magnetic measurements, and molar conductivities. IR

spectra showed that the ligand acts as a neutral tridentate species coordinating to

Cu(II), Co(II), or Ni(II) through the pyridyl nitrogen, azomethine nitrogen, and

carbonyl oxygen. It had been suggested that the Schiff base can also act as a

mononegative tridentate ligand coordinating to Fe(III) or Cr(III) through the

pyridyl nitrogen, azomethine nitrogen, and carboxyl oxygen after displacement of

hydrogen from the hydroxyl group. The results suggest tetrahedral geometry

around Co(II) and Ni(II), octahedral geometry around Fe(III) and Cr(III), and

square-planar geometry around Cu(II).

Complexes of the type [M(apabh)Cl] and [M(Hapabh)(H2O)SO4], where

M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II); Hapabh = acetone p-amino

acetophenone benzoylhydrazone were synthesized and characterized [70].

Electronic spectra and µeff values suggested a square planar geometry for Co(II),

Ni(II) and Cu(II) chloro complexes and octahedral geometry for the sulfato

complexes. ESR data showed isotropic spectra for [Cu(apabh)Cl] and axial

spectra for [Cu(Hapabh)(H2O)SO4] and dx2

−y2 as the ground state for both Cu(II)

complexes. The ligand acts as tridentate monobasic in all chloro complexes

bonding through two >C=N- and a deprotonated enolate groups, whereas

13

tridentate neutral in all sulfato complexes coordinating through two >C=N- and a

>C=O groups. Thermal analysis (TGA & DTA) of [Ni(apabh)Cl] complex

indicated a multi-step exothermic decomposition pattern.

Coordination complexes of Co(II) and Cu(II) with Pyrrolyl-2-carboxaldehyde

isonicotinylhydrazone were synthesized and characterized [71] by elemental

analysis, conductance measurements, magnetic susceptibility measurements,

1H NMR spectroscopy, IR spectroscopy, UV-Vis absorption spectroscopy, ESR

spectroscopy and thermal analysis. IR spectra suggested that the ligand would act

as a dibasic donor coordinating through the azomethine nitrogen atom and enolic

oxygen atom. ESR and ligand field spectra suggested a tetrahedral geometry for

Co(II) complex and a square planar geometry for Cu(II) complexes.

Complexes of the type [M(apash)Cl] and [M(Hapash)(H2O)SO4], where

M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II); Hapash = acetone p-amino

acetophenone salicyloyl hydrazone were synthesized and characterized [72] by

elemental analyses, molar conductance, magnetic moments, electronic, ESR and

IR spectra, thermal studies (TGA & DTA) and X-ray diffraction studies. The

ligand coordinates through two >C=N and a deprotonated enolate group in all the

chloro complexes, whereas through two >C=N– and a >C=O group in all the

sulfato complexes. The electronic spectra suggested a square planar geometry for

Co(II), Ni(II) and Cu(II) chloride complexes and an octahedral geometry for the

sulfate complexes. ESR data showed an isotropic symmetry for [Cu(apash)Cl] and

[Cu(Hapash)(H2O)SO4] in solid state. The X-ray diffraction parameters for

[Co(apash)Cl] and [Cu(Hapash)(H2O)SO4] complexes were indexed for a

14

tetragonal and an orthorhombic crystal lattices, respectively. Thermal studies of

[Co(apash)Cl] complex showed a multi-step decomposition pattern. Most of the

complexes showed better antifungal activity than the standard miconazole against

a number of pathogenic fungi.

Saghatforoush et al [73] described the synthesis and characterization of two

new Zn(II) and Cd(II) complexes of the tetradentate dissymmetric Schiff base,

2-((E)-(2-(2-(pyridine-2-yl)ethylthio)ethylimino)methyl)-4-bromophenol,

prepared from 1-(2-pyridyl)-3-thia-5-aminopentane and 5-bromosalicylaldehyde.

The complexes were synthesized by treating an ethanolic solution of the ligand

with equimolar amounts of appropriate metal salts in 1 M methanolic solution of

NaOH or alternatively, by a more direct route in which the two reactants are

added to a solution of the ligand immediately after formation of the latter and

prior to any isolation. The complexes were characterized by elemental analysis,

FTIR, 1H-NMR, electronic spectra and molar conductivity. The probable

coordination geometries of Zn and Cd in these complexes with mixed N, S and O

donor atoms are tetrahedral - and octahedral-like, respectively. Both complexes

were found to be 1:1 electrolyte systems in acetonitrile.

Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes with a potentially

tridentate Schiff base, formed by condensation of 2-amino-3-carboxyethyl-4,5-

dimethylthiophene with salicylaldehyde were synthesized by Daniel and

co-workers [74] and characterized on the basis of elemental analyses, molar

conductance values, magnetic susceptibility measurements, UV–Vis and IR

spectral data.

15

Mn(II) and Co(II) complexes with 1-benzotriazol-2-yl-1-[(p-methoxyphenyl)-

hydrazono]propan-2-one (BMHP) were synthesized and characterized [75] by the

elemental analysis, magnetic and different spectral techniques. Proton dissociation

constant of the free ligand and the stepwise stability constants of its metal

complexes were determined potentiometrically in 0.1 M KC1 and 40% (v/v)

ethanol-water. The dissociation process was found to be non-spontaneous,

endothermic and entropically unfavorable. The values of (-∆G0) and (-∆H

0) were

in the order: Mn(II) < Co(II) < Ni(II) < Cu(II), in accord with the Irving-Williams

order [51]. The complexes were found to be stabilized by both enthalpy and

entropy changes and the results suggested that complexation is an enthalpy-driven

process. The distribution diagrams of the complexes in solution were evaluated.

El-Wahab [76] synthesized Co(II), Ni(II), Cu(II) and Zn(II) complexes of two

Schiff base ligands bearing organic acid moiety, N-(2-thienylmethylidene)-2-

amino-4-chlorobenzoic acid and N-(2-hydroxybenzylidene)-2-amino-4-

chlorobenzoic acid and characterized on the basis of analytical data, molar

conductance, IR, 1H NMR, UV–Vis, mass spectra, magnetic measurements,

thermal analysis and X-ray powder diffraction technique. The molar conductance

data revealed that these complexes were non-electrolytes. The ligands were

coordinated to the metal ions in a terdentate manner with ONO/ONS donor sites

of the carbonyl oxygen, azomethine nitrogen and phenolic oxygen or thiophenic

sulphur. An octahedral structure was proposed for the prepared metal complexes

and some ligand field parameters (Dq, B and β) in addition to CFSE were

calculated. The thermal stability of the metal complexes was also evaluated.

16

Jeragh and co-workers [77] synthesized and characterized the Schiff base,

3-(3-hydroxypyridin-2-ylimino)-1-phenylbutan-2-one (HPIB). The proton-ligand

dissociation constant of HPIB and the stepwise stability constants of Cu(II),

Ni(II), Co(II), and Mn(II) complexes were also determined potentiometrically in a

40 % (v/v) ethanol-water mixture in the presence of 0.100 M KCl under nitrogen

at different temperatures. The stabilities of the complexes follow the order:

Cu > Ni > Co > Mn. The dissociation constants of HPIB and the stability

constants, log K, of its metal complexes and the corresponding thermodynamic

parameters were derived and discussed. The proton-ligand dissociation was found

to be nonspontaneous, endothermic, and entropically unfavorable. The different

thermodynamic parameters suggested that the complex formation was an

enthalpydriven process. The speciation of the complexes was determined.

The solid complexes of Mn(II), Fe(III), Co(II) and Cu(II) with Schiff bases

derived from 3-acetyl-6-methyl-(2H)-pyran2,4(3H)dione (dehydroacetic acid) and

3-chloroaniline and 3-aminophenol, were synthesized and characterized [78] by

elemental analysis, conductometry, thermal analysis, magnetic, IR, NMR, UV-Vis

spectral studies and X-ray powder diffraction. From the analytical data, the

stoichiometry of the complexes was found to be 1:2 (metal:ligand). The low

conductance values suggested that the complexes were non-electrolytes. IR

spectral data showed that the ligand behaved as a dibasic bidentate ligand with N,

O-donor ligand towards metal ions. The powder X-ray diffraction study suggested

that the complex had monoclinic crystal system with P2/m space group. The

17

physico-chemical data indicated that all the complexes possess octahedral

geometry. They were also screened for antifungal activity.

A chiral Schiff base N-(S)-2-(6-methoxylnaphthyl)-propanoyl-N ′-(2-

hydroxylbenzylidene) hydrazine (H2L) had been synthesized [79]. Reaction of

H2L with Cu(OAc)2·H2O led to the formation of a metal complex

{[CuL]·H2O·2DMF}∞. In the complex, the potential dinegative tridentate

L2−

ligand acting as tetradentate bridging ligand coordinate to two metal ions so as

to form a novel infinite metal–organic coordination chain structure. The

enantiomerically pure ligand H2L presents two different sets of signals in the 1H

NMR spectrum either in chloroform solution or in dimethylsulfoxide solution,

showing the presence of both (E) and (Z) isomers. The X-ray structural

investigations of H2L revealed that it is the fully extended E-configuration in the

solid state.

Complexes of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) with 4-[2'-hydroxy

salicylidene 5' (2"-thiozlylazo] chlorobenzene were synthesized and characterized

[80] by elemental analysis, molar conductance, magnetic susceptibility, spectral

studies, IR, electronic, ESR and X-ray diffraction studies. The metals coordinate

with Schiff base nitrogen atom, azo nitrogen atom and phenolic hydroxyl oxygen

atom of the ligand. The ONN donor ligand acts as a tridentate ligand in all

complexes. The spectral analysis indicated tetrahedral geometry for Co(II), Ni(II),

Zn(II) and Cd(II) complexes while distorted tetrahedral geometry for Cu(II)

complex. The X-ray powder diffraction of some complexes suggested tetragonal

18

crystal system. The ligand and complexes had been screened for their

antimicrobial activity against some bacterial and fungal activity.

Stability constants of some metal complexes of 1-Phenyl-2-[2-hydroxy-3-

sulfo-5-nitrophenylazo] butadione-1,3 synthesized from benzoylacetone were

determined [81] by potentiometric and conductometric titrations. The stability of

these complexes decreased in the following order: Fe > Cu > UO2 > Ni > Co > Zn

> Cd > Mn > Mg > Ca.

Equilibrium studies [82] of the Schiff base complex systems viz. Co(II),

Ni(II), Cu(II) and Zn(II)-vanillin (van) (A) and -L-valine (val)/L-glutamine

(gln)/L-glutamic acid (glu)/L-histidine (his) (B) demonstrated the presence of

MAB, MA2B or MA2B2 complexes. The stability constant values in the M(II)-van-

val/gln/glu systems indicated that the Schiff base ligand (AB) was tridentate in its

M(AB) complexes, while it was tetradentate in the M(II)-van-his systems. The

results showed that the MA2B and MA2B2 complexes can best be represented,

respectively, as M(AB)A and M(AB)2.

Al-Kandary and co-workers [83] reported synthesis and characterization of

Zn(II), Cd(II), Pb(II), Hg(II) and phenylmercury(II) complexes of 4-amino-6-

hydroxy-2-mercapto pyrimidine (AHMP) on the basis of elemental analyses, IR

and 1H NMR measurements. The stoichiometry of the complexes was found to be

1:2 except for the phenylmercury(II) complex where the ratio was 1:1. In these

complexes, the ligand was bonded to the metal through its sulfur atom. The

potentiometric results showed the formation of both 1:1 and 1:2 complexes and

the corresponding stability constants were determined for both Zn2+

and Cd2+

ions.

19

The high insolubility of Hg(II), phenylmercury(II) and Pb(II) complexes

prevented the determination of their stability constants. The concentration

distribution of the complexes in solution was evaluated. The effect of temperature

on the dissociation constant of AHMP and the formation constants of both the

Zn-AHMP and Cd-AHMP complexes were studied and the thermodynamic

parameters were calculated.

A new dipodal ligand, N,N′-bis{2-[(2-hydroxybenzylidine)amino]ethyl}

malonamide (BHAEM) was synthesized [84] by Schiff base condensation of

N,N′-bis(2-aminoethyl)malonamide with two equivalent of salicylaldehyde and

characterized on the basis of elemental analyses and various spectral data. The

complexation reaction of the ligand with H+, Co

2+, Ni

2+, Cu

2+and Zn

2+ in solution

was investigated by spectrophotometric and potentiometric method. Two

protonation constants of BHAEM assigned for two hydroxyl groups of aromatic

ring were determined and its hydrolysis mechanism was proposed through

potentiometric result. In presence of metal ions, BHAEM shows different

coordination properties. All metal ions form ML type complex where the ligand

coordinates to the metal ion through two N-amine and two O-phenolate groups. In

addition, Ni2+

and Cu2+

form additional complex species of the type MLH−1 and

MLH−2, respectively due to ionization of amide protons.

Schiff bases derived from the condensation of 3-hydrazino-6-

methyl[1,2,4]triazin-5(4H)one and aromatic aldehyde derivatives formed [85]

Co(II) and Ni(II) complexes. The structural formulae, the mode of bonding,

and geometry of the complexes were characterized by elemental and thermal

20

analyses as well as IR, electronic spectra, molar conductance and magnetic

moment measurements.

Esin et al [86] determined the stoichiometric protonation constants of

L-tyrosine, L-cysteine, L-tryptophane, L-lysine, and L-histidine, and their methyl

and ethyl esters in water and ethanol–water mixtures of 30, 50, and 70%(v/v)

ethanol, potentiometrically using a combined pH electrode system calibrated as

the concentration of hydrogen ion. Titrations were performed at 25∘C and the

ionic strength of the medium was maintained at 0.10 mol⋅L−1 using sodium

chloride. Protonation constants were calculated by using the BEST computer

program [87]. The effect of solvent composition on the protonation constants is

discussed. The log10 K2 values of esters generally decreased with increasing

ethanol content. However, the log10 K1 values of the esters of L-tyrosine,

L-cysteine, and L-tryptophane were found to increase with increasing ethanol

content in contrast those of L-lysine and L-histidine esters.

Protonation constant of an unsymmetrical Schiff base, salicylidene(N-

benzoyl)glycyl hydrazone (SalBzGH), and formation constants of its complexes

were determined [88] potentiometrically at different temperatures in aqueous

dioxane medium. Complexes of SalBzGH with VO(IV), Mn(II), Co(II), Ni(II),

Cu(II), Zn(II), Cd(II) and Hg(II) had been prepared. Elemental analyses,

pH-metric, molar conductance, magnetic susceptibility, electronic, IR, ESR, XRD

(powder) and NMR studies was carried out to study the coordination behaviour of

SalBzGH toward these metal ions. pH-metric and 1H NMR studies showed the

presence of two dissociable protons in the ligand. IR and NMR spectra suggested

21

the tridentate nature of the ligand, coordinating as a uninegative species in the

Mn(II) complex and as a dinegative species in all the other complexes. Presence

of two different conformers of the ligand at room temperature and stabilization of

a single conformer upon complex formation was established from 1H NMR

spectra of the metal-free ligand, Zn(II) and Hg(II) complexes recorded at 296 K.

Electronic and ESR spectra indicated highly distorted tetragonal geometry for

VO(IV) and Cu(II) complexes. XRD powder patterns of the Zn(II) complexes

were indexed for an orthorhombic crystal system.

Reddy et al [89] synthesized Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)

complexes of a dibasic bis-chelating ligand, 5-acetyl 2,4-dihydroxy acetophenone

semicarbazone (H2-ADAS) and characterized on the basis of their elemental

analyses, conductivity, magnetic moments, IR and electronic spectral data. Metal

to ligand ratio in all the chelates had been found to be 1:1. The Schiff base

behaves in a dibasic pentadentate manner with OO and ONN donor atoms. All the

complexes had been assigned octahedral stereochemistry. The ligand H2-ADAS

forms polymeric metal complexes with first row divalent transition metal ions.

Complexes of Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and UO2(VI) with N-(2-

pyrdylidene)-benzothiazole-2-ylacetohydrazone were prepared [90] in ethanolic

solution and characterized by physical and spectral methods. IR, electronic, TGA,

and ESR spectra of the complexes, as well as IR, 1H NMR and mass spectra of the

ligand had been obtained. IR spectra showed that the ligand coordinates as an

anionic tridentate ligand via the azomethine nitrogen, pyridyl nitrogen and enolic

oxygen. A tetrahedral structure was proposed for Co(II) and Ni(II) complexes

22

while an octahedral structure was suggested for the Fe(III) complexes. All Cu(II)

complexes had square-planar geometry.

Golcu et al [91] reported the synthesis and potentiometric studies of Cd(II)

and Cu(II) complexes of 4-[(4-bromo-phenylimino)-methyl]-benzene-1,2,3-triol,

4-[(3,5-di-tert-butyl-4-hydroxy-phenylimino)-methyl]-benzene-1,2,3-triol, 3-(p-

tolyl imino-methyl)-benzene-1,2-diol, 3-[(4-bromo-phenylimino)-methyl]-

benzene-1,2-diol, and 4-[(3,5-di-tert-butyl-4-hydroxy-phenylimino)-methyl]-

benzene-1,3-diol. The structure of the ligands and their complexes was

investigated using elemental analysis, FT-IR, UV–Vis, 1H and

13C NMR, mass

spectra, magnetic susceptibility and conductance measurements. In the complexes,

all the ligands behaved as bidentate ligands, oxygen in the ortho position and

azomethine nitrogen atoms of the ligands coordinate to the metal ions. The keto-

enol tautomeric forms of these Schiff bases had been investigated in polar and

non-polar organic solvents. Protonation constants of these Schiff bases and

stability constants of their Cu(II) and Cd(II) complexes were determined in 50 %

DMSO–water media at 25.00 ± 0.02°C under nitrogen atmosphere and ionic

strength of 0.1 M sodium perchlorate. All the Schiff bases had been observed to

possess two protonation constants. The variation of protonation constant of these

compounds was interpreted on the basis of structural effects associated with the

substituents. Cu2+

and Cd2+

ions formed stable 1:2 complexes with these bases.

Co(L)2, Ni(L)2, Cu(L)2 and Zn(L)2 complexes were synthesized [92] from

p-aminoacetophenoneoxime and 5-Chlorosalicylaldehyde and Co(AcO)2.4H2O or

Ni(AcO)2 or Cu(AcO)2.H2O or Zn(AcO)2.2H2O in 1:2 molar ratio, employing a

23

template approach. Based on elemental analyses, molar conductivity and magnetic

susceptibility data, IR, 1H and

13C NMR and UV-Vis spectra, as well as thermal

analyses (TG), a tetrahedral geometry for the complexes was determined. The data

showed that the ligand coordinates to the metal ion via –C=N- and –C-O- groups.

Omar and Mohamed [93] reported the synthesis and characterization of

Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Pd(II) and UO2(II) chelates

of 1-(2-thiazolylazo)-2-naphthalenol (TAN). The dissociation constants of the

ligand and the stability constants of the metal complexes were calculated

pH-metrically at 25°C and 0.1 M ionic strength. The solid complexes were

characterized by elemental and thermal analyses, molar conductance, IR, magnetic

and diffuse reflectance spectra. The molar conductance data revealed that the

chelates are non-electrolytes. IR spectra showed that the ligand was coordinated to

the metal ions in a terdentate manner with ONN donor sites of the naphthyl OH,

azo N and thiazole N. An octahedral structure was proposed for Mn(II), Fe(III),

Co(II), Ni(II), Zn(II), Cd(II) and UO2(II) complexes and a square planar structure

for Cu(II) and Pd(II) complexes. The thermal behaviour of these chelates showed

that water molecules (coordinated and hydrated) and anions were removed in two

successive steps followed immediately by decomposition of the ligand molecule

in the subsequent steps.

Garg and co-workers [94] prepared and characterized the complexes of Cu(II),

Ni(II), Co(II), and Zn(II) with 2-[2-(6-methylbenzothiazolyl)azo]-5-

dimethylamino benzoic acid by elemental analysis, vibrational spectra, magnetic

susceptibility measurements, conductance measurements and EPR spectra.

24

Stability constants had been evaluated potentiometrically. Electronic spectra,

magnetic susceptibility measurements and molecular modeling studies support a

distorted square planar geometry around the metal ions. Vibrational spectra

indicated the coordination of the azo group, nitrogen of benzothiazole, the

carboxylate anion and the acetate ion on complexation with the metal ion. All

complexes were found to be monomers.

The stability of the complexes followed the order: Cu(II) > Ni(II) > Co(II) > Zn(II).

The binary and mixed-ligand complexes formed between ligands (histidine (His),

histamine (Him) and glycine (Gly)) and some transition metals (Cu(II), Ni(II) and

Zn(II)) were studied potentiometrically [95] in aqueous solution at (25.0 ± 0.1)ºC

and ionic strength 0.10 M KCl in order to determine the protonation constants of

the free ligands and stability constants of binary and ternary complexes. The

complexation model for each system has been established by the software

program BEST [87] from the potentiometric data. The most probable binding

mode for each binary species of histidine and for all mixed species was also

discussed based upon derived equilibrium constants and stability constants related

to the binary species. The ambidentate nature of the histidine ligand, i.e. the

ability to coordinate histamine-like, imidazolepropionic acid-like and glycine-like

modes was indicated from the results obtained. The concentration distributions of

various species formed in solution were also evaluated. In terms of the nature of

metal ion, the complex stability followed the trend: Cu(II) > Ni(II) > Zn(II), which

was in agreement with the Irving-Williams order [51].

25

4-Acrylamidobenzenesulfonylazide (ABS) was synthesized [96] and

characterized by elemental analyses and IR spectroscopy. Proton-monomeric

ligand dissociation and metal-monomeric ligand stability constants of ABS with

some metal ions were also determined potentiometrically in 0.1 M KCl and a 50

% (v/v) ethanol–water mixture. In the presence of 2, 2'-azobisisobutyronitrile as

an initiator, the dissociation and stability constants of ABS were determined in its

polymeric form (PABS). The influence of temperature on the dissociation of ABS

and the stability constants of its complexes in monomeric and polymeric forms

were precisely studied. The pKH value of PABS was found to be higher than that

for ABS, indicating that the vinyl group in the monomeric form decreases the

electron density and hence reduces the N bond H bond strength. The stability

constants of the metal complexes with the polymeric form were higher than those

of the monomeric form. This revealed that the ligand in a polymeric form could be

considered as a better complexing agent.

Hankare et al [97] synthesized and characterized Mn(II), Co(II), Ni(II), Cu(II),

Zn(II), Cd(II) and Hg(II) complexes of a Schiff base obtained by condensation of

5-(2'-thiazolylazo) salicylaldehyde and p-methoxy aniline by elemental analysis,

magnetic susceptibility, molar conductance, IR, electronic spectra, ESR and

thermal analysis (TGA). The ONN environment of the metal ion was realized in

the complexes by involvement of the -N=N- group in coordination. The analysis

of magnetic moment and electronic spectral data indicated tetrahedral geometry

for the complexes except Cu(II) complex which had a distorted tetrahedral

geometry.

26

Kabir et al [98] determined the stability constants (∆ log K) of the ternary

Cu(II) and Ni(II) complexes of folic acid and some amino acids such as

tryptophane, tyrosine, dipicolinic acid and adenosine triphosphate by

pontentiometric method and their redox behavior had been examined by cyclic

voltammetric method. A statistical increased in the value of mixed ligand

formation constants was observed by small negative or positive value of ∆ log K.

The pontentiometric and cyclic voltammetric study showed that Ni(II) complexes

were more stable than Cu(II) complexes.

Dogan and co-workers [99] determined the stoichiometric protonation

constants for some -amino acids (glycine, L-alanine, L-methionine,

L-phenylalanine, and L-threonine), the Schiff bases derived from them and

2-hydroxy-1-naphthaldehyde, along with the stoichiometric stability constants of

Schiff base–Mn(III) complexes. These equilibrium constants were determined

potentiometrically using a combined pH electrode system calibrated in

concentration units of the hydrogen ion at 25°C, and at an ionic strength of 0.10

mol-dm-3

NaCl in 30 and 50 % dimethyl sulfoxide–water mixtures. The

calculations of these constants were carried out using the PKAS and the BEST

[87] computer programs. In addition, the effects of solvent composition and

structures on the protonation and the complex formation constants were

investigated. The mole ratio of Mn(III) to amino acid-Schiff bases was also

determined and it was found that the complexes were of the MnL2 type.

The protonation constants of a number of mono-substituted anilines were

determined [100] potentiometrically in 0, 20, 30, 40, 50, and 60 % (v/v) dioxane –

27

water mixtures at (25.00 ± 0.02)0C at an ionic strength of 0.1 mol·dm

-3 in sodium

perchlorate. The data from the potentiometric titrations were evaluated using the

BEST [87] computer program. The trends in the values of the protonation

constants of anilines were explained in terms of the nature of substituent and the

solute–solvent and solvent–solvent interactions. Furthermore, the effects of the

substituents on the basicity of aniline, the additivies of these effects, and the

applicability of the Hammett equation to the behavior of these substituents are

discussed.

Formation and protonation constants of seventeen Schiff bases-derived from

2-hydroxyaniline with some substituted benzaldehydes, and the stability constants

of Cu(II) complexes of these Schiff bases were determined [101]

potentiometrically in 20, 40, and 60%(v/v) dioxane–water media. The data from

the potentiometric titrations were evaluated with the BEST [87] computer

program. For all Schiff bases studied, it was observed that the log KOH values

related to the protonation equilibria of the phenolic oxygen increase while the log

KNH values related to the protonation equilibria of the azomethine nitrogen

decrease with increase in the dioxane content. The variation of these constants

was discussed on the basis of specific solute–solvent interactions and structural

changes of Schiff bases from water to the dioxane–water media. The titrimetric-

pH investigation of substituted benzilidene-2-hydroxyaniline systems had also

revealed the formation of stable mono-Schiff base complexes with Cu+2

ion.

The proton dissociation constant of 5-(40-sulfonylazidophenylazo)-3-phenyl-

2-thioxothiazolidin-4-one (SPT) and the stability constants of its complexes with

28

some metal ions were calculated [102] potentiometrically in 0.1 M KCl and 40 %

(v/v) ethanol–water mixture. The order of stability was found to be Mn < Co < Ni

< Cu < Zn. The effect of temperature on the dissociation of SPT and the stability

of its complexes were studied. The corresponding thermodynamic functions were

derived and discussed. The dissociation process is unspontaneous, endothermic,

and entropically unfavorable. The formation of the metal complexes was found to

be spontaneous, endothermic and entropically favorable.

Raman et al [103] carried out the synthesis of Cu(II), Co(II), Ni(II) and Zn(II)

chelates with a new Schiff base derived from benzil-2,4-dinitro-phenylhydrazone

with aniline. Microanalytical data, molar conductance, and magnetic susceptibility

values have been obtained, and IR,1H NMR,

13C NMR, UV-Vis, CV and EPR

spectral studies have been carried out to suggest tentative structures for the

complexes.

Ni(II) and Cu(II) complexes with Schiff bases 4-dimethylaminobenzylidene-4-

chloroanilinc (DABCA)/4-dimethylaminobenzylidene-4-bromoaniline(DABBA)

/4-dimethylamino benzylidene-3-nitroaniline (DABNA) of general formula

ML(H2O)2Cl2.2H2O and MLCl2(H2O)2.2H2O have been synthesized [104].

Coordination of azomethine nitrogen in the Schiff base to the metal has been

proposed. Ligand field parameters of some of the complexes have been calculated.

The dissociation constant of 4-sulfamethoxazoleazo-3-methyl-2-pyrazolin-5-

one and metal-ligand stability constants of its complexes with Mn2+

, Co2+

, Ni2+

and Cu2+

ions have been determined [105] potentiometrically in 0.1 M KCl and

40 % ethanol-water mixture. The order of the stability constants of the complexes

29

decreases in the sequence Cu > Ni > Co > Mn. The effect of temperature was

studied and the corresponding thermodynamic parameters (∆G, ∆H, and ∆S) were

derived and discussed. The dissociation of the ligand and the formation of the

metal complexes were spontaneous, endothermic, and entropically favourable.

Mukherjee et al [106] investigated the complex formation equilibria of Co(II),

Ni(II), Cu(II) and Zn(II) with anthranilic acid N, N-diacetic acid (H3ada) in the

absence and presence of 1,10-phenanthroline (phen), bipyridine (bipy),

ethylenediamine (en), glycinate (gly-) and oxalate (ox

2-) (B) in aqueous solution at

25′ 1°C at a fixed ionic strength 0.1 M (NaNO3) pH-metrically and indicates the

formation of simple binary complexes M(ada) and M(B) and ternary complexes

M(ada)(B). M(ada)(B) complexes are formed according to equilibria M(B) +

adaH M(ada)(B) + H, with B = phen and bipy, and M(ada) + BH M(ada)(B) + H,

with B = en, gly- and ox

2- ligands.

A tripodal tetraamine ligand N{(CH2)3NH2}{(CH2)2NH2}2 (pee), has been

investigated [107] as an asymmetrical tetraamine chelating agent for bivalent Co,

Ni, Cu, Zn and Cd metal ions. The protonation constants for this ligand and the

formation constants for its complexes have been determined potentiometrically in

0.1 M KCl at 25°C. The successive protonation constants (log Kn) are: 10.22,

9.51, 8.78 and 1.60 (n = 1-4). One complex with formula M(pee)2 (M = Co, Ni,

Cu, Zn and Cd) is common to all five metal ions and the formation constant (log

βML) is: 12.15, 14.17, 16.55, 13.35 or 9.74, respectively. In addition to the simple

complexes, Co, Cu and Zn also give hydroxo complexes, and Cu and Ni give

complexes with monoprotonated pee. [Zn(pee)](ClO4)2 and [Cd(pee)Cl](ClO4)

30

complexes were isolated and are believed to have tetrahedral and trigonal-

bipyramidal structures, respectively.

Merce et al [108] reported the stability constants of the complexes Al(III),

Cd(II), Gd(II) and Pb(II) with vitamin D3 in a 30/70 % v/v water-ethanol medium

at 25.0°C. The logarithms of the overall stability constants are: 1 = 12.4 ± 0.5,

7.6 ± 0.3, 9.33 ± 0.07, and 9.1 ± 0.5, respectively, whereas the logarithms of 2

are 24.4 ± 0.5 (Al3+

), 14.3 ± 0.3 (Cd2+

), and 15.4 ± 0.5 (Pb2+

). Gd3+

ion forms only

the 1:1 complex. These values are compared to those reported previously and

correlations are established between the stability constants and physical

properties, such as the ionization energy.

Acid-base equilibria and metal ion chelating tendency of 3-(acetophenone

hydrazone)-6-phenylpyridazine (AHP) and its para-substituted derivatives

(XAHP), X = NH2, Cl, Oil and OMe were potentiometrically investigated [109] in

75 % (v/v) dioxane-water at 298 K and 0.1 M KNO3. For the same metal ion, the

order of stability decreases in the sequence: NH2AHP > OHAHP > OMeAHP >

AHP > CIAHP, which is the same order of decreasing the electron-repelling

property of the substituent (X) and consequently the basicity of the ligands. The

thermodynamic parameters have been evaluated.

Kubicek et al [110] synthesized bis(aminomethyl)phosphinic acid,

(NH2CH2)2PO2H (HL), using a new procedure and studied its coordination ability

towards Co(II)/(III), Ni(II), Cu(II) and Zn(II) both in solution and in the solid

state. Because of the presence of two nitrogen atoms, the ligand exhibits a higher

overall basicity than common (aminoalkyl)phosphinic acids. Consequently, the

31

values of the determined stability constants are comparable with those found for

(aminoalkyl)phosphonic acids. NMR titrations of Zn(II) point to the interaction of

phosphinate with the metal ion in a strong acid solution. The X-ray structures

show several coordination modes in the solid state. In Co(II)/(III), Ni(II), Cu(II)

complexes, the central ion is octahedrally coordinated with two phosphinate

oxygen atoms, two molecules of water and two chlorides in all-trans arrangement.

Participation of the donor groups in crystals isolated from neutral solutions

depends on the metal ion. In the zinc(II) complex, two phosphinate oxygen atoms

and two amine nitrogen atoms (trans to each other) of two different ligand

molecules are coordinated in an equatorial plane and two amino groups of the two

other ligand molecules are bound in axial positions. Thus, each molecule of the

amino acid forms a five-membered N, O-chelate to one Zn+2

ion and the other

amino group is bound to the neighbouring ion creating an infinite chain. Ni forms

a trans-O,O -[Ni(H2O)2(L-N,N)2] complex in which the metal ion is chelated by

four amine nitrogen atoms forming two six-membered chelates in an equatorial

plane and the octahedron is completed with two water molecules at the apical

positions. The phosphinate group is not coordinated. The above results point to a

relatively low coordination ability of the phosphinate group; however, due to its

low pKA, it is able to bind metal ions at lower pH than other coordinating groups

do.

Garg et al [111] carried out the chemical-speciation and molecular modelling

studies for accessing the interactions of metal ions with some amide containing

ligands by using the BEST program [87] and method of Bjerrum and

32

Calvin [48,49] as modified by Irving and Rossoti [51] has been used to find out

the values of stability constants. The order of stability constants is found to be

fairly in agreement to Irving-Williams order [52]. Molecular modelling studies

have been carried out to determine the ideal site for metal binding to the ligands

PCPAH and PCBAH.

Weyhermüller and co-workers [112] described the ligating properties of a

tridentate ligand, methylamino-N,N-bis(2-methylene-4,6-dimethylphenol), H2L,

with [O,N,O]-donor atoms and characterized its complexes [Fe(III)2L3] (1),

[Fe(III)L2]− (1a), [Mn(IV)L2] (2), [Mn(III)L2]

− (2a), and [Cr(III)L2]

− (3) by

various physical techniques, including IR, MS, UV–Vis, electrochemical, EPR,

Mössbauer and magnetic susceptibility measurements. Complex 1 contains a

dinuclear Fe2L3 unit with two different 5- and 6-coordinated Fe(III) centers. The

overall geometry around the Mn(IV) ion in 2 and the Cr(III) ion in 3 is best

described as a distorted meridional octahedron with two trans-positioned nitrogens

of the aminebis(phenolate) ligand. The isoelectronic [Cr(III)L2]−

(3) and

[Mn(IV)L2] (2) with distinctive metal–ligand covalent binding characteristics have

been used as probes for comparison of EPR spectra. Complex 2 containing

Mn(IV) with its higher ionic charge and covalency has a significantly larger zero-

field splitting parameter D than that of Cr(III) in 3. That the electrochemical

oxidations are ligand-centered, i.e. formation of phenoxyl radicals from the

coordinated phenolates, except for the Mn(III) compound 2a, where the first

oxidation occurs at metal center generating Mn(IV) species 2, have been shown

by voltammetric methods.

33

PS-LCuDMF, PS-LNi3DMF, PS-LCo3DMF, PS-LFeCl2DMF, PS-LZnDMF,

PS-LCdDMF, PS-LMn3DMF, PS-LMoO2DMF, PS-LZr(OH)

22DMF and PS-

LUO2DMF (DMF = dimethylformamide compounds were synthesized [113] by

the reaction of metal salt/metal coordination compound with the polystyrene

supported Schiff base (PS-LH2) obtained by the reaction of chloromethylated

polystyrene, 3-formylsalicylic acid and ethanolamine compounds and

characterized by elemental analyses, IR, electronic, ESR spectral and magnetic

susceptibility measurements. The Cu(II), Ni(II), Co(II), Fe(III) and Mn(II)

compounds are paramagnetic while the Zn(II), Cd(II), Zr(IV), Mo(VI) and U(VI)

compounds are diamagnetic. The magnetic and ESR data indicate the

magnetically dilute nature of the metal centres. The shifts of the

v(C=N)(azomethine), ν(C-O)(phenolic) and ν(C-O)(alcoholic) stretches have been

monitored to find out the donor sites of PS-LH2. A square planar structure for

PS-LCuDMF; a tetrahedral structure for PS-LZnDMF and PS-LCdDMF; an

octahedral structure for PS-LNi3DMF, PS-LCo3DMF, PS-LFeCl2DMF, PS-

LMn3DMF, PS-LMoO2DMF and PS-LUO

2DMF have been suggested for the

compounds. PS-LZr(OH)22DMF is pentagonal bipyramidal.

A new ligand, N-isonicotinoyl-N'-thiobenzoylhydrazine (HINTB), has been

prepared [114] by the reaction of isonicotinic acid hydrazide and carboxym ethyl

dithiobenzoate. The addition complexes [M(HINTB)2Cl2] [M=Co(II), Ni(II),

Zn(II)], [Cu(HINTB)Cl2], M(HINTB)2(CH3COO)2 [M=Co(II), Ni(II)] and

deprotonated complexes [Cu(INTB)(CH3COO)] and [Zn(INTB)2] also have been

prepared and characterized by elemental analyses, magnetic susceptibility,

34

electronic, NMR and IR spectral data. The room temperature ESR spectra of

[Cu(HINTB)Cl2] and [Cu(INTB)(CH3COO)] are characteristic of monomeric and

dimeric species, respectively.

Hacht et al [115] performed a quantitative study of Zn(II) and Cu(II) complex

formation with orotic acid under physiological conditions (37°C; 0.15 mol-dm-3

NaCl) using the glass electrode potentiometric technique. Several species have

been identified within the pH range 2–10 for the metal-to-ligand concentration

ratios investigated. Three mononuclear complexes, ML, ML2, and ML2H-1, have

been characterized with both metals. In addition, the polynuclear species M3L2H-2

has been found with Cu(II). Formation constants for all these species have been

calculated with the help of the SUPERQUAD computer program [116]. UV

absorption and IR spectroscopic measurements combined with speciation

calculations have been used to confirm corresponding structures.

2-Acrylamidosulphadiazine (ASD) was synthesized [117] and characterized

by elemental analyses, IR and 1H NMR spectra. Proton-monomeric ligand

dissociation and metal-monomeric ligand stability constants of ASD with some

metal ions were determined potentiometrically in 0.1 M KCl and 40 % (v/v)

ethanol-water mixture. In the presence of 2,2′-azobisisobutyronitrile as initiator,

the dissociation and stability constants of ASD were determined in polymeric

form (PASD). The influence of temperature on the dissociation of ASD and the

stability constants of their complexes in monomeric and polymeric forms were

critically studied. The pK2H value of PASD was found to be higher than ASD, this

means that the vinyl group in the monomeric form decreases the electron density

35

and hence reduces the N–H bond strength. The stability constants of the metal

complexes in polymeric form are higher than those of the monomeric form. This

is quite reasonable because the ligand in a polymeric form is considered as a better

complexing agent.

Proton-ligand dissociation and metal-ligand stability constants of

cinnamaldehyde anthranilic acid (CAA) with some transition metal ions were

determined potentiometrically [118] in 0.1 M KCl and 50 % (v/v) ethanol–water

mixture. The effect of temperature on the dissociation of CAA and the stability of

its complexes were studied in monomeric and polymeric forms. The

corresponding thermodynamic functions were derived and discussed. The

dissociation process is non-spontaneous, endothermic and entropically

unfavourable. Formation of the metal complexes was spontaneous, endothermic

and entropically favourable.

The equilibria involved in the formation of Mn(II), Fe(II), Co(II), Ni(II),

Zn(II) complexes with different ligands like (1) di-N-phenyl pyromellitic di-

imide, (2) di-N-pyridyl pyromellitic di-imide, (3) N-2,thiazolin O-amino

benzamide, (4) 4-oxo-4(2-thiazolin) amino butanoic acid (5) 4-oxo-4(2-thiazolin

amino butenoic acid), (6) 3-hydroxy pyridine 2-carboxamide were studied by pH

titration technique [119] at different ionic strength, different percentages of

solvent and different temperatures. The stability constants of the binary complexes

have been evaluated by Irrving and Rossotti’s method [50]. The variation of the

stability of binary metal complexes is discussed in terms of the effect of (1) ionic

36

strength (2) dielectric constant (3) temperature and (4) correlation of stabilities of

metal complexes.

Matho and Chandra [120] isolated the complex compounds of pyridine-3-

carboxylic acid hydroxy methyl amide, LH with Ni(II), Cu(II), Fe(II) and Cr(III)

and characterized on the basis of their elemental analysis, IR, magnetic and

electronic studies. The tridentate character of the ligand and the presence of

intrahydrogen bonding in it are evidenced from the IR spectral study. It forms

complex with Cu(II) and Cr(III) after losing one proton (H+) from its imidolic

form at pH 8 but no proton is lost in the formation of Ni(II) and Fe(II) complexes

at pH = 6. The complexes are tetrahedral except Cu(II) complex, which is square

planar. All complexes are paramagnetic.

Deepa et al [121] carried out synthesis and characterization of a series of

transition metal complexes of N-methyl and N-ethyl acetoacetanilide isonicotinyl

hydrazones (L1H2 and L

2H2 respectively) by using elemental analysis, magnetic

susceptibility measurements and UV-VIS, IR,1H NMR spectral studies. IR

spectral studies revealed that the ligand behaves as tridentate di- or mono-anions

co-ordinating through the anilide oxygen and isonicotinyl carbonyl oxygen and

azomethine nitrogen atoms. Thermogravimetric studies of Mn(II), Co(II), Ni(II)

and Cu(II) complexes of N-methyl acetoacetanilide (L1H2) were also carried out.

Antifungal studies of L2H2 and Mn(II), Co(II), Ni(II) and Cu(II)andZn(II)

complexes of both the ligands were also carried out.

Equilibrium-based computer models on eight Schiff base complex systems,

viz. Co(II)/Ni(II)/Cu(II)/Zn(II)-2-pyridinecarboxaldehyde(A)-L-threonine (thr)

37

and L-glutamin (gln) (B) systems demonstrated [122] the formation of Schiff base

complexes having the stoichiometry MAB, MA2B and Ma2B2. The Schiff base

(AB) binds the metal ion in a tridentate manner. Tetrahedral geometry for CoAB

and NiAB, square-planar geometry for CuAB and octahedral geometry for

M(AB)2 complexes are indicated.

Transition metal complexes of furfurylidene(N-benzoyl)glycyl hydrazone,

FBzGH, of the formulae [M(FBzGH)2Cl(H2O)]Cl (M = Mn, Cu, Zn, Cd, Hg),

[Co(FBzGH)2]Cl2·H2O and [Ni(FBzGH)2Cl2]·H2O were isolated [123] from acidic

solutions and the complexes [M(FBzG)2 (H2O)2] (M = Co, Ni, Cu), from neutral

solutions. Elemental analyses, molar conductances, magnetic susceptibilities,

electronic, pH-metric, ESR, IR, and NMR studies had been carried out on these

complexes to illuminate the ligational behavior of FBzGH toward the divalent

metal ions. Formation constants of the metal chelates were determined

pH-metrically in aqueous-dioxane. Bidentate nature of the hydrazone coordinating

as a neutral species in the adducts and as a uninegative one in the neutral

complexes was suggested. 1H NMR spectra indicated the presence of two different

conformers of the ligand at room temperature even after complexation which

would coalescent at a temperature higher than 340 K indicating that one of the

conformers was stabilized. A highly shielded chemical shift value of 113

Cd NMR

showed a strongly bound but weakly coordinated Cd2+

ion.

38

The literature survey reveals the following noteworthy points:

1. There are reports on the synthetic, magnetic and spectral studies of

transition metal complexes of a number of hydrazones in aqueous and

organic media.

2. Amidst the abundant literature on the transition metal complexes of

various N, O-donor ligands, a considerable number of reports appear on

the determination of the stability constants and thermodynamic parameters

of the transition metal complexes. However, most of the studies reported

were carried out in aqueous and/or mixed solvent media.

3. There are a few reports on the complexes of N-benzoylglycine hydrazide

and its hydrazones with transition metal ions [88, 123, 124-129] and

lanthanide ions [130-138].

4. There is no report in the literature till date on the complexation reactions,

stability constants and thermodynamic data of the transition metal

complexes of Schiff bases derived from N-benzoylglycine hydrazide in

aqueous, organic and/or aqueous-micellar media.

We have, thereof, synthesized two novel Schiff bases from the condensation

of N-benzoylglycine hydrazide with two carbonyl containing compounds,

4-dimethylaminobenzaldehyde and 3-aminoacetophenone, and carried out a

detailed study on the interactions of the transition metal ions with the two bases

employing potentiometric titration and various physico-chemical techniques.

Proton - ligand and metal - ligand formation constants of the bases and their

39

Ni(II), Cu(II) and Cd(II) complexes along with the thermodynamic parameters

associated with the protonation and complexation reactions have been evaluated.

The studies have been carried out in both aqueous and micellar media containing

nonionic and ionic surfactants and the effect of the micelles on the reactions are

being studied. The Cu(II), Ni(II) and Cd(II) complexes are also isolated and

characterized. Studies have also been made on the spectral properties of the

complexes. Results of the investigations are described in the following chapters.

40

References

1. Y. L. Angelique and J. M. Thomas. Metal complexes as enzyme inhibitors.

Chem. Rev., 99:9, 2711 -2734 (1999).

2. D. R. Richardson and P. V. Bernhardt. Crystal and molecular structure of

2-hydroxy-1-naphthaldehyde isonicotinoyl hydrazone (NIH) and its

iron(III) complex: an iron chelator with anti-tumour activity. JBIC, 4, 266-

2 (1999).

3. Y. Zheng-Yin, Y. Ru-Dong, L. Fa-Shen and Y. Kai-Bei. Crystal structure

and antitumour activity of some rare earth metal complexes with schiff

base. Polyhedron, 19, 2599-2604 (2000).

4. J. L. Buss, J. Neuzil and P. Ponka. Oxidative stress mediates toxicity of

pyridoxal isonicotinoyl hydrazone analogs. Archives of Biochemistry and

Biophysics, 421, 1-9 (2004).

5. L. Sommer, W. P. Maung-Gyee and D. E. Ryan. Heterocyclic hydrazones

of o-hydroxyaldehyde as analytical reagents. Ser. Fac. Sci. Natur. Univ.

Purkynianae 2:6, 115-128 (1972).

6. H. Shargi and M. A. Nasser. Schiff-base metal(II) complexes as new

catalysts in the efficient, mild and regioselective conversion of 1,2-

epoxyethans to 2-hydroxy-ethyl thiocyanates with ammonium thiocyanate.

Bull. Chem. Soc. (Jpn), 76, 137-142 (2003).

7. P. D. Beer. Charged guest recognition by redox responsive ligand systems.

Adv. Mater., 6, 607-609 (1994).

41

8. F. C. J. M. Van Veggel, G. Chiosis, B. R. Cameron and D. N. Reinhoudt.

Preorganized metalloreceptor: Selective receptor for NH3. Supramolecular

Chem., 4, 177-183 (1994).

9. T. Nabeshima. Regulation of ion recognition by utilizing information at

the molecular level. Coord. Chem. Rev., 148, 151-169 (1996).

10. J. W. Canary and B. C. Gibb. Selective recognition of organic molecules

by metallohosts. Prog. Inorg. Chem., 45, 1-81 (1997).

11. J. M. Gray. Metallacrown ethers: Unique inorganic ligands. Comments

Inorg. Chem., 17, 95 (1995).

12. V. L. Pecoraro, A. J. Stemmler, B. R. Gibney, J. J. Bodwin, H. Wang, J.

W. Kampf and A. Barwinski. Metallacrowns: a new class of molecular

recognition agents. Prog. Inorg. Chem., 45, 83-177 (1997).

13. F. B. Dwyer, E. Mayhew, E. M. F. Roe and A. Shulman. Inhibition of

landschuetz ascites tumor growth by metal chelates derived from 3,4,7,8-

tetramethyl-1,10-phenanthroline. Brit. J. Cancer., 19, 195-199 (1965).

14. M. J. M. Campbell. Transition metal complexes of thiosemicarbazide and

thiosemicarbazones. Coord. Chem. Rev., 15, 279-319 (1975).

15. D. R. Williams. Metal, ligands and cancer. Chem. Rev., 72, 203-213

(1972).

16. A. Furst and R.T. Haro. Survey of metal carcinogenesis. Prog. Expt.

Tumor Res., 12, 102-133 (1969).

42

17. V. W. W. Yam and K. K. W. Lo. Recent advances in utilization of

transition metal complexes and lanthanides as diagnostic tools. Coord.

Chem. Rev., 184, 158-240 (1999).

18. G. B. Gardner, D. Venkataraman, J. S. Moore and S. Lee. Spontaneous

assembly of a hinged coordination network. Nature, 374, 792-793 (1995).

19. D. Venkataraman, G. B. Gardner, S. Lee and J. S. Moore. Zeolite-like

behavior of a coordination network. J. Am. Chem. Soc., 117, 11600-11601

(1995).

20. O. M. Yaghi, G. Li and H. Li. Selective binding and removal of guests in a

microporous metal-organic framework. Nature, 378, 703-706 (1995).

21. T. L. Hennigar, D. C. MacQuarrie, P. Losier, R. D. Rogers and M. J.

Zaworotko. Supramolecular isomerism in coordination polymers:

Conformational freedom of ligands in [Co(NO3)2(1,2-bis(4-pyridyl)

ethane)1.5]. Angew. Chem., Int. Ed. Engl., 36:9, 972-973 (1997).

22. S. Z. Vatsadze, V. N. Nuriev and N. V. Zyk. Synthesis of azoles with two

pyridine substituents at carbon atoms and their use in coordination

chemistry. Chem. Heterocycl. Compd., 41:9, 1091-1101 (2005).

23. S. Kitagawa, R. Kitaura and S.-i. Noro. Functional porous coordination

polymers. Angew. Chem., Int. Ed. Engl., 43, 2334-2375 (2004).

24. C. Janiak. Engineering coordination polymers towards applications.

Dalton Trans., 14, 2781-2804 (2003).

25. P. Nguyen, P. Gomez-Elipe and I. Manners. Organometallic polymers with

transition metals in the main chain. Chem. Rev., 99:6, 1515-1548 (1999).

43

26. B. Olenyuk, S. Leininger and P. J. Stang. Self-assembly of discrete cyclic

nanostructures mediated by transition metals. Chem. Rev., 100, 853-907

(2000).

27. G. F. Swiegers and T. J. Malefetse. New self-assembled structural motifs

in coordination chemistry. Chem. Rev., 100, 3483-3537 (2000).

28. M. N. Hughes. The Inorganic Chemistry of Biological Processes, 2nd

edn.,

John Wiley & Sons: New York. (1981).

29. J. A. Cowan. Inorganic Biochemistry: An Introduction, Wiley-VCH: New

York, (1997).

30. H. Sigel and A. Sigel Eds. Metal Ions in Biological Systems, Marcel

Dekker, Inc: New York, 23 (1988).

31. J. R. Lancaster. The Bioinorganic Chemistry of Nickel. VCH Publishers:

New York, (1988).

32. E. L. Andronikashvili, V. G. Bregadze and J. R. Monaselidze. Interactions

between nickel and DNA considerations about the role of nickel in

carcinogenesis. Met. Ions Biol. Syst., 23, 331-357 (1988).

33. R. Chandra, R. Beri and A. Sarkar. Antitumor activity of some metal

complexes: effect on hepatic DNA, RNA, and protein synthesis in rats

bearing transplanted tumors by Dalton's lymphoma cells. J. Inorg.

Biochem., 48:1, 1-14 (1992).

34. E. W. Ainscough, A. M. Brodie, A. J. Dobbs, J. D. Ranford and J. M.

Waters. Antitumour copper(II) salicylaldehyde benzoylhydrazone (H2sb)

complexes: physicochemical properties and the single-crystal X-ray

44

structures of [{Cu(H2sb)(CCl3CO2)2}2] and [{Cu(Hsb) (ClO4)

(C2H5OH)}2] and the related salicylaldehyde acetylhydrazone (H2sa)

complex, [Cu(Hsa)Cl(H2O)]·H2O. Inorg. Chim. Acta., 267, 27-38 (1998).

35. Z. L. Lu, W. Xiao, K. B. Yu, L. R. Deng, S. Kang, C.Y. Su and J. Liu.

Bivalent transition metal complexes of 4, 5-diazafluorene-9-one

benzoylhydrazone (HL) and the characterization of weak interaction in

CoL2(H2O)2. J. Mol. Struct., 553, 91-99 (2000).

36. M. B. Hursthousse, S. A. A. Jayaweera and A. Quick. Crystal and

molecular structure of [acetone benzoyl hydrazonido (1-)-N'O] dichloro-

oxo (triphenylphosphine) - rhenium(v). J. Chem. Soc., Dalton Trans., 279

(1979).

37. Y. M. Liang, C. M. Liu, Y. X. Ma and Q. S. Li. Formylferrocene 5-

phenyloxazole-2-carbonylhydrazone bivalent transition metal complexes.

Transition Met. Chem., 23, 97-99 (1998).

38. R. Haran, J. Gairin and G. Commenges. Gallium-71, carbon-13 and

hydrogen-1NMR studies of the interactions of pyridoxal 5′-phosphate

isonicotinyl hydrazone with gallium in aqueous solution. Inorg. Chim.

Acta., 46, 63-67 (1980).

39. T. Rudolph and J. P. Phillips. Heterocyclic hydrazones from 8-

quinolinols. Anal. Chim. Acta., 34, 235-237 (1966).

40. R. K. Parashar, R. C. Sharma, A. Kumar, and G. Mohan. Stability studies

in relation to IR data of some schiff base complexes of transition metals

45

and their biological and pharmacological studies. Inorg. Chim. Acta., 151,

201-208 (1998).

41. M. Gallego, M. Garcia-Vargas and M. Valcarcel. Pyridine-2-carbaldehyde

2-hydroxybenzoylhydrazone as a selective reagent for the extraction and

spectrophotometric determination of iron(II). Analyst, 104, 613-619

(1979).

42. T. Soldatovic, V. Vasic and Z. D. Bugarcic. Effects of micelles on the

complex formation of [PtCl(dien)]+ with biologically relevant ligands.

Bull. Chem. Soc. Jpn. 79:12, 1889-1893 (2006).

43. M. J. Rosen. Surfactants and interfacial phenomena. 2nd

edn., Wiley

Interscience: New York, (1998).

44. S. E. Price, D. Japper, P. Lorenzo, J. E. Saaveda, J. A. Hrabie and K. M.

Davies. Micellar catalysis of nitric oxide dissociation from

diazeniumdiolates. Langmuir, 19, 2096-2102 (2003).

45. A. K. Mapari and K. V. Mangaonkar. Stability constants of mixed ligand

complexes of transition metal(II) ions with N-(2-Hydroxy-1-

naphthylidene)-2,6-diisopropylaniline as primary ligand and N-(2-

Hydroxybenzylidene)-2,3- dimethylaniline as secondary Ligand. E-

Journal of Chemistry, 8:1, 123-126 (2011).

46. D. T. Tayade, D. A. Pund, R. A. Bhagwatkar, D. B. Rathod and N. A.

Bhagwatkar. pH metric studies of interaction of synthesized ligands 2-

amino-4-hydroxy-6-methylpyrimidine and 1-(4-hydroxy-6-

methylpyrimidino)-3-phenylthiocarbamide with Cu(II), Cd(II), Cr(II)

46

cations at 0.1 M ionic strength. International Journal of Chemistry, 3:1,

36-41 (2011).

47. J. Bjerrum. Metal ammine formation in aqueous solution. P. Hasse and

Son: Copenhagen, 63 (1941).

48. M. Calvin and K. W. Wilson. Stability of chelate compounds. J. Am.

Chem. Soc., 67, 2003-2007 (1945).

49. B. M. Kalshetty, R. C. Sheth, R. R. Chavan and M. B. Kalashetti. Role of

temperature on stability constants of metal complexes in 50% (v/v) water-

ethanol solution. International Journal of Applied Biology and

Pharmaceutical Technology, 2:1, 97-101 (2011).

50. H. M. Irving and H. S. Rossotti. The calculation of formation curves of

metal complexes from pH-titration curves in mixed solvents. J. Chem.

Soc., 2904-2910 (1954).

51. H. M. Irving and R. J. P. Williams. The stability of transition-metal

complexes. J. Chem. Soc., 3192–3210 (1953).

52. P. S. Reddy, P. V. Ananthalakshmi and V. Jayatyagaraju. Synthesis and

structural studies of first row transition metal complexes with tetradentate

ONNO donor schiff base derived from 5-Acetyl 2,4-

dihydroxyacetophenone and ethylenediamine. E-Journal of Chemistry,

8:1, 415-420 (2011).

53. A. C. Tella, J. A. Obaleye and G. K. Obiyenwa. Spectrophotometric study

of stability constants of dapsone- Cu(II) complex at different temperatures.

Journal of Pharmacy Research, 4:1, 241-244 (2011).

47

54. A. E. Angkawijaya, A. E. Fazary, E. H. M. Taha and Yi-Hsu Ju. Iron(III),

chromium(III), and copper(II) complexes of L-norvaline and ferulic acid.

J. Chem. Eng. Data, 56:3, 532-540 (2011).

55. P. Gans, A. Sabatini and A. Vacca. Investigation of equilibria in solution.

Determination of equilibrium constants with the HYPERQUAD suite of

programs. Talanta, 43:10, 1739-1753 (1996).

56. A. Afkhami, H. Keypour, F. Khajavi, and M. Rezaeivala. Application of

rank annihilation factor analysis to the spectrophotometric determination

of the formation constants of complexes of a new schiff base and some

transition metals in different media. J. Chem. Eng. Data, 55:11, 4725-4731

(2010).

57. E. I. Askar, H. Shokry and D. Al. Hashmy. Potentiometric and

conductometric studies of malonyl bis(salicyloylhydrazone) and divalent

metal complexes. Journal of Saudi Chemical Society, 14, 175-182 (2010).

58. S. A. Patil, V. H. Naik, A. D. Kulkarni, and P. S. Badami. DNA cleavage,

antimicrobial, spectroscopic and fluorescence studies of Co(II), Ni(II) and

Cu(II) complexes with SNO donor coumarin Schiff bases. Spectrochim.

Acta. A: Mol. Biomol. Spectrosc., 75:1, 347-354 (2010).

59. D. P. Singh, V. Malik, R. Kumar and K. Kumar. Synthesis and spectral

study of biologically active macrocyclic complexes of divalent transition

metal ions. Koord. Khim., 36:3, 221-226 (2010).

60. A. S. Munde, A. N. Jagdale, S. M. Jadhav and T. K. Chondhekar.

Synthesis, characterization and thermal study of some transition metal

48

complexes of an asymmetrical tetradentate Schiff base ligand. J. Serb.

Chem. Soc., 0:0, 0–11 (2010).

61. B. Dede, F. Karipcin and M. Cengiz. Synthesis, characterization and

extraction studies of N,N"-bis[1-biphenyl-2-hydroxyimino-2-(4-

acetylanilino) -1-ethylidene]-diamines and their homo and heteronuclear

copper(II) complexes. Journal of Chemical Sciences, 121:2, 163–171

(2009).

62. B. K. Kanungo, M. Baral, S. K. Sahoo and S. E. Muthu. Synthesis,

spectroscopic and theoretical studies of two novel tripodal imine-phenol

ligands and their complexation with Fe(III). Spectrochim. Acta. A: Mol.

Biomol. Spectrosc., 74:2, 544-552 (2009).

63. M. M. Omar, G. G. Mohamed and A. A. Ibrahim. Spectroscopic

characterization of metal complexes of novel Schiff base. Synthesis,

thermal and biological activity studies. Spectrochim. Acta. A: Mol. Biomol.

Spectrosc., 73:2, 358-369 (2009).

64. K. B. Vyas, G. R. Jani and M. V. Hathi. Potentiometric studies on

transition metal complexes of substituted derivative of coumarin-part 1. E-

Journal of Chemistry, 6:4, 1121-1124 (2009).

65. Y. Altun, F. Koseoglu, H. Demirelli, I. Yilmaz, A. Cukurovali and N.

Kavak. Pontentiometric studies on Ni(II), Cu(II) and Zn(II) metal

complexes with new Schiff bases containing cyclobutane and thiazole

groups in 60% dioxane-water mixture. J. Braz. Chem. Soc., 20:2, (2009).

49

66. S. A. Shaker, Y. Farina and A. A. Salleh. Synthesis and characterization of

mixed ligand complexes of 8-hydroxyquinoline and o-

hydroxybenzylidene-1-phenyl-2,3-dimethyl-4-amino-3-pyrazolin-5-on

with Fe(II), Co(II), Ni(II) and Cu(II) ions. Eur. J. Sci. Res., 33:4, 702-709

(2009).

67. N. Galic, Z. Cimerman and V. Tomisic. Spectrometric study of tautomeric

and protonation equilibria of o-vanillin schiff base derivatives and their

complexes with Cu(II). Spectrochim. Acta. A: Mol. Biomol. Spectrosc.,

71:4, 1274-1280 (2008).

68. S. Prasad and R. K. Agarwal. Nickel(II) complexes of hydrazone of

isoniazid and their magneto-spectral, electrochemical, thermal and

antimicrobial investigations. International journal of inorganic chemistry

Research Letters in Inorganic Chemistry, 2008 (2008).

69. N. M. Hosny and F. I. El-Dossoki. Schiff base complexes derived from 2-

acetylpyridine, leucine, and some metal chlorides: Their preparation,

characterization, and physical properties. J. Chem. Eng. Data, 53:11,

2567-2572 (2008).

70. V. P. Singh and A. Katiyar. Synthesis, spectral characterization and

antimicrobial activity of some transition metal(II) complexes with acetone

p-amino acetophenone benzoylhydrazone. Pestic. Biochem. Physiol., 92:1,

8-14 (2008).

71. S. H. Guzar and J. I. N. Qin-han. Synthesis, Characterization and spectral

studies of new cobalt(II) and copper(II) complexes of pyrrolyl-2-

50

carboxaldehyde isonicotinoylhydrazone. J. Appl. Sci., 8:13, 2480-2485

(2008).

72. V. P. Singh, A. Katiyar and S. Singh. Synthesis, characterization of some

transition metal(II) complexes of acetone p- amino acetophenone

salicyloyl hydrazone and their anti microbial activity. BioMetals, 21:4,

491-501 (2008).

73. L. A. Saghatforoush, A. Aminkhani, S. Ershad, G. Karimnezhad, S.

Ghammamy and R. Kabiri. Preparation of zinc(II) and cadmium(II)

complexes of the tetradentate schiff base ligand 2-((E)-(2-(2-(pyridine-2-

yl)-ethylthio)ethylimino)methyl)-4-bromophenol (PytBrsalH). Molecules,

13, 804-811 (2008).

74. V. P. Daniel, B. Murukan, B. S. Kumari and K. Mohanan. Synthesis,

spectroscopic characterization, electrochemical behaviour, reactivity and

antibacterial activity of some transition metal complexes with 2-(N-

salicylideneamino)-3-carboxyethyl-4,5-dimethylthiophene. Spectrochim.

Acta, Part A: Mol. Biomol. Spectrosc., 70:2, 403-410 (2008).

75. A. El-Dissouky, N. M. Shuaib, N. A. Al-awadi, A. B. Abbas and A. El-

Sherif. Synthesis, characterization, potentiometric and thermodynamic

studies of transition metal complexes with 1-benzotriazol-1-yl-1-[(p -

methoxyphenyl) hydrazono]propan-2-one. J. Coord. Chem., 61:4, 579-594

(2008).

76. Z. H. Abd El-Wahab. Mononuclear metal complexes of organic carboxylic

acid derivatives: Synthesis, spectroscopic characterization, thermal

51

investigation and antimicrobial activity. Spectrochim. Acta, Part A: Mol.

Biomol. Spectrosc., 67:1, 25-38 (2007).

77. B. Jeragh, D. Al-Wahaib, A. A. El-Sherif and A. El-Dissouky.

Potentiometric and thermodynamic studies of dissociation and metal

complexation of 4-(3-Hydroxypyridin-2-ylimino)-4-phenylbutan-2-one. J.

Chem. Eng. Data, 52, 1609-1614 (2007).

78. V. G. Mane, V. N. Patange and B. R. Arbad. Synthesis, structural and

thermal characterization and antifungal study of manganese(II), iron(III),

cobalt(II) and copper(II) complexes of N,O donor ligands. J. Indian Chem.

Soc., 84:11, 1086-1091 (2007).

79. L. Wu, G. Qiu, H. Teng, Q. Zhu, S. Liang and X. Hu. Potential tridentate

salicylaldehyde hydrazone of arylalkanoic acid coordinate to copper(II)

acting as dinegative tetradentate ligands. Inorg. Chim. Acta, 360:9, 3069-

3074 (2007).

80. L. V. Gavali and P. P. Hankarep. Synthesis and characterization of the

complexes of some transition metals with 4-[2’-hydroxy salicylidene -5’

(2” -thiazolyazo]Chlorobenzene. Journal of Physical Sciences, 11, 147-

155 (2007).

81. S. R. Gadzhieva, F. M. Chyragov and K. T. Makhmudov. Complexation of

copper(II) with azo derivatives of benzoylacetone. J. Anal. Chem., 62:11,

1028-1031 (2007).

52

82. M. S. Nair, S. S. Kumari and R. S. Josyphus. Schiff base complexes of

some metal ions with vanillin and amino acids. J. Indian Chem. Soc., 84,

739-741 (2007).

83. J. Al-Kandary, F. Mandani, A. Al-Jimaz, A. El-Sherif and Md. Shoukry.

Synthesis and thermodynamic investigation of 4-Amino-6-hydroxy-2-

mercapto pyrimidine (AHMP) complexes with some selected divalent

metal(II) ions. J. Solution Chem., 6:2, 247-257 (2007).

84. S. K. Sahoo, S. E. Muthu, M. Baral and B.K. Kanungo. Potentiometric and

spectrophotometric study of a new dipodal ligand N,N′-bis{2-[(2-

hydroxybenzylidine)amino]ethyl}malonamide with Co(II), Ni(II), Cu(II)

and Zn(II). Spectrochim. Acta. A: Mol. Biomol. Spectrosc., 63:3, 574-586

(2006).

85. A. H. Osman. Synthesis and characterization of cobalt(II) and nickel(II)

complexes of some schiff bases derived from 3-hydrazino-6-methyl[1,2,4]

triazin-5(4H)one. Transition Met. Chem., 31:1, 35-41 (2006).

86. C. Esin, G. Aysegul, D. Alev and K. Esma. The determination of

protonation constants of some amino acids and their esters by

potentiometry in different media. J. Solution Chem., 35:1, 5-19 (2006).

87. A. E. Martell and R. J. Motekaitis. Determination and use of stability

constants. 2nd

edn., VCH: New York, 49 (1992).

88. R. K. Lonibala, T. R. Rao and R. K. B. Devi. Protonation constant of

salicylidene(N-benzoyl)glycyl hydrazone and its coordination behaviour

towards some bivalent metal ions. J. Chem. Sci. 118:4, 327-334 (2006).

53

89. P. S. Reddy, B. Satyanarayana and Jayatyagaraju. Synthesis and structural

studies on divalent transition metal complexes of 5-acetyl 2,4-dihydroxy

acetophenone semicarbazone. J. Indian Chem. Soc., 83:12, 1204-1207

(2006).

90. H. M. El-Tabl and F. A. El-Saied. Synthesis, magnetic and spectral studies

of Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and uranyl complexes of N-(2-

pyrdylidene)-Benzothiazole-2-Ylacetohydrazone. Synth. React. Inorg.

Met-Org. Nano-Met. Chem., 35, 245-252 (2005).

91. A. Golcu, M. Tumer, H. Demirelli and R. A. Wheatley. Cd(II) and Cu(II)

complexes of polydentate schiff base ligands: Synthesis, characterization,

properties and biological activity. Inorg. Chim. Acta, 358:6, 1785-1797

(2005).

92. E. Canpolat. Synthesis and characterization of a new 5-Chlorosalicyliden-

p-aminoacetophenoneoxime and its complexes with Co(II), Ni(II) and

Zn(II). Russ. J. Coord. Chem., 31:11 (2005).

93. M. M. Omar and G. G. Mohamed. Potentiometric, spectroscopic and

thermal studies on the metal chelates of 1-(2-thiazolylazo)-2-naphthalenol.

Spectrochim. Acta, Part A: Mol. Biomol. Spectrosc., 61:5, 929-936 (2005).

94. B. S. Garg, R. K. Sharma and E. Kundra. Copper(II), nickel(II), cobalt(II)

and zinc(II) complexes of 2-[2-(6-methylbenzothiazolyl)azo]-5-

dimethylamino benzoic acid: Synthesis, spectral, thermal and molecular

modelling studies. Transition Met. Chem., 30:5, 552-559 (2005).

54

95. A. Yuksel and K. Fitnat. Stability of Copper(II), Nickel(II) and Zinc(II)

binary and ternary complexes of histidine, histamine and glycine in

aqueous solution. J. Solution Chem., 34:2, 213-231 (2005).

96. B. J. A. Jeragh and A. El-Dissouky. Potentiometric and thermodynamic

studies of 4-Acrylamidobenzenesulfonylazide and its metal complexes in

monomeric and polymeric forms. J. Solution Chem., 33:5, 427-435

(2004).

97. P. P. Hankare, L. V. Gavali, V. M. Bhuse, S. D. Delekar and R. S.

Rokade. Synthesis and characterization of tridentate Schiff's base derived

from 5-(2'-thiazolylazo)salicylaldehyde and p-methoxy aniline and their

Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) complexes. Ind. J.

Chem., Sect.A: Inorganic, physical, theoretical & analytical. 43:12, 2578-

2581 (2004).

98. M. A. Kabir, M. M. Huque and M. R. Ullah. Studies on formation

constants of some transition metal complexes containing folic acid as a

primary ligand and some amino acids as secondary ligands. J. Indian

Chem. Soc., 81, 65-67 (2004).

99. A. Dogan, I. Sakiyan and E. Kilic. Potentiometric studies on some -amino

acid-schiff bases and their manganese(III) complexes in dimethyl sulfoxide–water

mixtures at 25°C. J. Solution Chem., 33:12, 1539-1547 (2004).

100. H. Demirelli and F. Koseoglu. Solvent and substituent effects on the

protonation of anilines in dioxane–water mixtures. J. Solution Chem., 33:12,

1501-1515 (2004).

55

101. H. Demirelli, F. Koseoglu and N. Kavak. Potentiometric studies of

copper(II) complexes of some substituted benzylidene-2-hydroxyanilines

in dioxane–water media. J. Solution Chem., 33:11, (2004).

102. A. T. Mubarak. Potentiometric and thermodynamic studies of 5-(4′-

Sulfonylazidophenylazo)-3-phenyl-2-thioxothiazolidin-4-one and its metal

complexes. J. Solution Chem., 33:2, 149-155 (2004).

103. N. Raman, S. Ravichandran and C. Thangaraja. Copper(II), cobalt(II),

nickel(II) and zinc(II) complexes of Schiff base derived from benzil-2,4-

dinitrophenylhydrazone with aniline. J. Chem. Sci., 116:4, 215-219 (2004).

104. T. Vivek, S. Rashmi and A. P. Mishra. Synthesis of some schiff base

complexes of nickel(II) and copper(II) derived from p-

dimethylaminobenzaldehyde. J. Indian Chem. Soc., 81, 147-149 (2004).

105. A. A. Al-Sarawy. Potentiometric and thermodynamic studies of 4-

Sulfamethoxazoleazo-3-methyl-2-pyrazolin-5-one and its metal

complexes. Chem. Pap., 58:2, 109-112 (2004).

106. G. N. Mukherjee, S. Bandyopadhyay and A. Das. Complex formation of

some 3d-metal(II) ions with anthranilic acid N, N-diacetic acid in the

absence and in the presence of some typical bidentate (N,N), (N,O) and

(O,O) donor ligands. J. Indian Chem. Soc., 80:1, 7-10 (2003).

107. K. Hassan, D. Masoud, S. Sadegh and P. W. Kevin. Potentiometric

determination of the formation constants for complexes of 3,2', 2"-

triaminopropyldiethylamine with cobalt(II), nickel(II), copper(II),zinc(II)

and cadmium(II). Transition Met. Chem., 28:4, 425-429 (2003).

56

108. A. L. R. Merce, L. S. Yano, M. A. Khan, X. D. Thanh and G. Bouet.

Complexing power of vitamin D3 toward various metals. Potentiometric studies of

vitamin D3 complexes with Al3+

, Cd2+

, Gd3+

, and Pb2+

ions in water–ethanol

solution. J. Solution Chem., 32:12, 1075-1085 (2003).

109. H. S. Seleem. Stability constants and thermodynamics of complexation of

Schiff base hydrazones derived from 3-hydrazino-6-phenylpyridazine and

acetophenone derivatives. J. Indian Chem. Soc., 80:6, 622-625 (2003).

110. V. Kubicek, P. Vojtisek, J. Rudovsky, P. Hermann and I. Lukes.

Complexes of divalent transition metal ions with

bis(aminomethyl)phosphinic acid in aqueous solution and in the solid

state. Dalton Trans., 3927- 3938 (2003).

111. B. S. Garg, R. K. Sharma, R. Shrestha, S. Mittal and M. Sarbhai. Metal-

pyridyl carboxy propanamide (PCPAH) and metal-pyridyl carboxy

benzamide (PCBAH) interactions; Stability constant, chemical-speciation

and molecular modelling studies. Indian J. Chem., 41A:8, 1625-8(Sc)

(2002).

112. T. Weyhermuller, T. K. Paine, E. Bothe, E. Bill and P. Chaudhuri.

Complexes of an aminebis(phenolate) [O,N,O] donor ligand and EPR

studies of isoelectronic, isostructural Cr(III) and Mn(IV) complexes.

Inorg. Chim. Acta, 337, 344-356 (2002).

113. A. Syamal, D. Kumar, A. K. Singh, P. K. Gupta, Jaipal and L. K. Sharma.

Synthesis and characterization of a chelating resin containing ONO donor

tridentate Schiff base and its coordination compounds with copper(II),

57

nickel(II), cobalt(II), iron(III), zinc(II), cadmium(II), manganese(II),

molybdenum(VI), zirconium(IV) and uranium(VI). Indian J. Chem.,

41A:7, 1385-1390 (2002).

114. N. K. Singh and D. K. Singh. Synthesis, spectroscopic characterization,

and biological activity of N-isonicotinoyl- N'-thiobenzoylhydrazine

complexes of Co(II), Ni(II), Cu(II) and Zn(II). Synth. React. Inorg. Met-

Org. Nano-Met. Chem., 32:2, 203-218 (2002).

115. B. Hacht, H. Tayaa, A. Benayad and M. A. Mimouni. Potentiometric and

spectroscopic investigation of copper(II)– and zinc(II)–orotate complex equilibria

under physiological conditions. J. Solution Chem., 31:9, 757-769 (2002).

116. P. Gans, A. Sabatini and A. Vacca. Superquad: An improved general

program for computation of formation constants from potentiometric data.

J.Chem. Soc., Dalton Trans., 1195-1200 (1985).

117. R. M. Issa, A. Z. El Sonbati, A. A. El Bindary and H. M. Kera. Polymer

complexes XXXIV. Potentiometric and thermodynamic studies of

monomeric and polymeric complexes containing 2-

acrylamidosulphadiazine. Eur. Polym. J., 38:3, 561-566 (2002).

118. Z. El-Sonbati, A. A. El-Bindary and N. A. El-Deeb. Polymer complexes

XXXII: Potentiometric and thermodynamic studies of cinnamaldehyde

anthranilic acid and its metal complexes in monomeric and polymeric

forms. Reactive and Functional Polymers. 50:2, 131-138 (2002).

58

119. S. Kantaiah and P. Lingaiah. Stability constants of binary metal complexes

of Mn(II), Fe(II), Co(II), Ni(II), Zn(II) with ‘N’-‘O’ donor ligands. Acta

Cienc Indica- Chem., 28:1, 9-24 (2002).

120. C. B. Matho and S. Chandra. Complex compounds of pyridine-3-

carboxylic acid hydroxy methyl amide with Ni(II), Cu(II), Fe(II) and

Cr(III). Acta Cienc Indica- Chem., 27:4, 151-4 (2001).

121. K. P. Deepa, K. K. Aravindakshan and F. Suharaf. Synthesis,

characterization and antifungal studies of trans. metal complexes of N-

methyl and N-ethyl acetoacetanilide isonicotinyl hydrazones. Asian J.

Chem., 13:4, 1549-59. (2001).

122. M. S. Nair and S. T. David. pH-metric and electronic spectral studies on

schiff base complex formation with some 3d-metal ions. J. Indian Chem.

Soc., 78, 308-309 (2001).

123. R. K. Lonibala, N. I. Devi R. K. B. Devi and T. R. Rao. Ligational

behaviour of furfurylidene (N-benzoyl)glycyl hydrazone towards some

transition metal ions. Synth. React. Inorg. Met.- Org. Chem., 31:1, 179-194

(2001).

124. R. K. Lonibala and T. R. Rao. Synthesis and characterization of the

complexes of some transition metals with 2-Acetyl Pyridine (N-benzoyl)

glycyl hydrazone. Proc. Indian Acad. Sci. (Chem. Sci.), 111:5, 615-616

(1999).

59

125. P. S. S. J. Sastry and T. R Rao. Coordinating behaviour of a tridentate

Schiff-base in its normal and hemi-acetal forms towards some 3d-metal

ions. Proc. Indian Acad. Sci. (Chem. Sci.), 107:2, 101-108 (1995).

126. R. K. Lonibala and T. R. Rao. X-Ray diffraction study of Zn(II)

complexes of 2-acetylpyridine(N-benzoyl)glycyl hydrazone. Cryst. Res.

Technol., 26, K77-K81 (1991).

127. T. R. Rao, Mamta Sahay and R. C. Aggarwal. Synthesis and

characterisation of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes of

acetone (N-benzoyl)glycyl hydrazone, Indian J. Chem., 24A, 79-81

(1985).

128. T. R. Rao, M. Sahay and R. C. Aggarwal. Synthesis and structural studies

of some bivalent 3d metal complexes of o-hydroxyacetophenone(N-

benzoyl)glycyl hydrazone. Synth. React. Inorg. Met.-Org Chem., 15, 175-

186 (1985).

129. T. R. Rao, M. Sahay and R. C. Aggarwal. Synthesis and structural studies

of some first row transition metal complexes of N-benzoylglycine

hydrazide. Synth. React. Inorg. Met.- Org. Chem., 15:2, 209-222 (1985).

130. P. A. Kumar and T. R. Rao. Studies on some rare earth metal complexes:

Ten-and six-coordinated complexes of an unsymmetrical aminoacid

derivative. Proc. Indian Acad. Sci. (Chem. Sci.), 109, 89-97 (1997).

131. G. Singh, P. A. Kumar and T. R. Rao. Studies on some lanthanide(III)

complexes of heterocyclic ligands. Coordinating behaviour of pyridoxal

60

(N-benzoyl)glycyl hydrazone in its hemiacetal form. J. Chem. Research

(M), 0861-0866 (1994).

132. T. R. Rao and G. Singh. Synthesis and spectral studies of some 4f-metal

complexes. Spectrochim. Acta. 47A:6, 727-736 (1991).

133. T. R. Rao and G. Singh. Spectral studies of N-benzoylglycine hydrazide,

acetone(N-benzoyl)glycyl hydrazone and their Ce(III) and Y(III)

complexes. Asian J. Chem., 2, 111-118 (1990).

134. T. R. Rao and G. Singh. Complexes of some lanthanides with the Schiff

base derived from 2-acetylpyridine and N-benzoylglycine hydrazide.

Indian J. Chem., 29A, 154-157 (1990).

135. T. R. Rao and G. Singh. Synthesis and spectral studies of lanthanide metal

complexes of acetone- (N-benzoyl)glycyl hydrazone. Svnth. React. Inorq.

Met.-Orq. Chem., 19, 263-278 (1989).

136. T. R. Rao, G. Singh and I. A. Khan. Coordinated lanthanide metal

complexes of N-benzoylglycine hydrazide. Transition Met.Chem., 14:1,

15-18 (1989).

137. T. R. Rao and G. Singh. Synthesis and structural studies of some trivalent

lanthanide metal complexes of o-hydroxyacetophenone (N-benzoyl)glycyl

hydrazone. Proc. Indian Acad. Sci. (Chem. Sci.)101, 219-226 (1989).

138. T. R. Rao and G. Singh. Synthesis and spectral studies of o-

hydroxyacetophenone (N-benzoyl)glycyl hydrazone and some of its

lanthanide(III) complexes. Transition Met. Chem., 14:6, 471-477 (1989).