Organometallic Chemistry: Synthesis, Structure and

Applications of Organochalcogens (S, Se, Te), -mercury

A. Synthetic Metals: Synthesis and structural characterization of organosulfur

-donors and acceptors for structure-property correlation

B. Systematic study of intramolecularly coordinated

organochalcogens (Se, Te):

1. E···D secondary bonding by X-ray and NMR etc.

D

EX

D = N, O

E = O, S, Se, Te

X = E, Halogens, Organyl groups

2. Isolation of novel species which are otherwise unstable, show unusual reactivity

3. Hybrid multidentate ligands containing both “hard” and

“soft” donor atoms: chiral, macrocyclic ligands

4. Synthetic organochalcogens with Glutathione Peroxidase

(GPx)-like activity

5. Monomeric, volatile stoichiometric organometallic precursors for

MOCVD of Group II-VI semiconductors

C. Metal Metal interactions (Hg)

Synthetic metals and Superconductors

1973

TTF.TNCQ First Organic Metal

(TMTSF)2ClO4

First Organic Superconductor

Tc ~ 1 K

(BEDT-TTF)2[Cu{N(CN)2}Cl]

Tc 12.5-12.8 K

S

S S

S

CN

CN

NC

NC

TTF TCNQ

S

S S

SS

SS

S

BEDT-TTF

Se

Se Se

Se

TMTSF

Synthetic metals and Superconductors

Singh et al.

J. Chem. Soc., Chem. Commun., 1991, 952.

J. Chem. Soc., Perkin Trans I, 1991, 3341.

Chemistry and Industry, Applied Higlights, 1991, P805.

J. Chem. Soc., Perkin Trans I, 1992, 2913.

J. Org. Chem., 1995, 60, 508.

J. Chem. Soc., Perkin Trans I, 1998, 1769.

Synthesis and Structural Characterization of

BEDT-TTF type - Donors/Acceptors

S

S S

S

S

S

S

S

(CH2)n(CH2)n

n = 4, 5, 6, 12

Major findings

(a) Core C6S8 more planar

(b) Donor properties unchanged

(c) S...S nonbonded interactions decrease

(d) n = 6 onwards, isomers

S

S S

S

S

S

S

S

(CH2)n

(CH2)n

Phane type TTFs isolated

(i) C6S8 core not planar

(ii) Poor donors

1. C6S8 Core planar

2. Stacked uniformly along a axis

3. S S 3.686 Å

BEDT-TTF 3.686 Å (core tub-shaped)

TTF-6 Isomers

PM-3 computed parameters

Energy = 68.56 kcal/mol Energy = 79.42 kcal/mol

S

S

S

S

S

S

S

S

S

X

S

S

S

S

Ph3P

S S

S

S S

S

S

S

S

S

S

S

S

S

S

SS

S

X

CH3

X = Cl, Br

Functionalised TTFs

Singh et al. Tetrahedron 1997, 11627.

Benzene

Thio-Claisen Rearrangement

(BMeEDT-TTF)8/3(CuCl2)

Normalised resistance vs temperature plot

RT

/R (

290K

)

Substrates for Intramolecularly Coordinated Organochalcogens

Singh et al.

J. Chem. Soc., Dalton Trans., 1990, 907.

Inorg. Chem., 1992, 32, 1431.

Organometallics, 1995, 14, 4755.

J. Chem. Soc., Dalton Trans., 1996, 2718.

J. Chem. Soc., Dalton Trans., 1996, 1203.

Organometallics, 1996, 15, 1707.

Organometallics, 1997, 16, 563.

Organometallics, 1999, 18, 1986.

Chem. Eur. J., 1999, 5, 1411.

Tetrahedron: Asymmetry, 1999, 10, 237.

Chem. Commun., 2000, 143.

Organometallics, 2003, 22, 5069.

Organometallics, 2004, 23, 4199.

Organometallics, 2006, 25, 382

Chemm. Commun., 2010, 46, 1130

Dalton Trans., 2010, 39, 2010

Dalton Trans., 2011, 40, 4489

Organometallics, 2011, 30, 534

Dalton Trans., 2012, 41, 10714

G

G = NMe2, Cl,OH, SPh

N

Me H

O

N

R1

R2

R1 = H, R2 = HR1 = H, R2 = EtR1 = Me, R2 = Me

O

N

NR*

NHR

O

Fe

CHO

Br

N

O

N

NN

N

O

Se

NO

Se

N

O

Se

Bi

N

O R

R´

SeX

N

O R

R´

BiCl3

n-BuLi

N

O R

R´

ELi

N

O R

R´

E

N

OR

E

N

O R

R´

Li

Hg

N

O

E

N

O

E M

N

O

N

O

E

N

O

Se

N

O

Se Hg

E(dtc)2

R = R´ = Me

R = Et, R ´ = H

E powder

[O]/H2O

R = R´ = Me (E = Se)

E = Se; E = Te

R = R´ = Me R = Et, R ´ = H

R = R´ = Me; E = Se R = Et, R ´ = H; E = Se R = R´ = Me; E = Te

R = R´ = Me; E = Se R = Et, R ´ = H; E = Se R = R´ = Me; E = Te

R´

R = R´ = Me

R = R´ = Me (E = Se)

E = Se; M = Zn E = Se; M = Cd E = Se; M = Hg

E = Te; M = Zn E = Te; M = Cd

R = R´ = Me

Br2 or I2

(E = Se)

R = R´ = Me; X = Cl R = R´ = Me; X = Br R = Et, R ´ = H; X = Br R = R´ = Me; X = I R = Et, R´ = H; X = I

A Typical Sequence of Reactions

Attempted synthesis of [8-(dimethylamino)-1-naphthyl]selenenyl(II) triflate

Se-N 1.862(5)

Se-C(9) 1.887(6)

Se O(2) 2.585(5)

N Se BrAgOTf, 0 oC

MeOH

XN Se OTf

N N

Se

Se

OTf

OTf

1. Coupling of naphthalene rings

2. Demethylation

3. Highly conjugated and blue color

van der Waals radii (Å)

O 1.52

Se 1.90 3.42

300 400 500 600 700 800

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Ab

so

rba

nce

Wavelength(nm)

pH 5.75

pH 6.06

pH 6.71

pH 7.15

pH 7.64

pH 8.50

pH 9.41

pH 9.93

pH 10.53

300 400 500 600 700 800

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Ab

so

rba

nce

Wavelength(nm)

Compound(20 M)

Compound (20 M)+base(30 M)

Compound (20 M)+base(30 M)+ acid(30 M)

pH titration studies of dication (pH sensor ?)

Possible mechanism

SanjioOrganochalcogens with two coordinating heteroatoms

13

Singh et al.,

Angew. Chem. Int. Edn., 2004, 43, 4513

J. Org. Chem. 2005, 70, 3693.

Significant Torsion Angles (˚) (Ar)

C6-C1-C2-C3 10.1(5)

C2-C3-C4-C5 -7.3(5)

C5-C6-C1-C2 -11.8(5)

All Torsion angles ( ˚ ) (Ar) ~ 0.0

C1-C6-C5-C4 0 .00

C1-C2-C3-C4 0.00

First example of coordinated RSeBr: Observation of aryl ring strainSelvakumar

Singh et al. Chem. Eur. J., 2010, 16, 1057614

Antioxidant enzymes

Catalase is a hemeprotein – Catalyzes the disproportion of H2O2

Superoxide dismutase: Cu-Zn-SOD, Fe-SOD, Mn-SOD– Catalyzes the disproportionation of HO2

Sulfiredoxine is a cysteine containing enzyme - Reduction of H2O2

Glutathione peroxidase is a selenocysteine containing enzyme - Reduction of H2O2

ROOH + 2GSH ROH + GSSG + H2OGPx

In 1973, Flohe & Rotruck discovered the antioxidant enzyme glutathione peroxidase (GPx)

In GPx-catalytic triad involves Sec, Trp and Glnresidues at the active side

Established as the 21st proteinogenic amino acid

Sec-codon UGA

Uniqueness of selenium

Sec least abundant in proteins

In adult human, 140 g S and only mg quantities of Se

Selenium more polarizable, nucleophile, lower redox potential

Flohe, L. Biochim Biophys Acta 2009, 179,1389-1403; Bock, A.; Forchhammer, K.; Heider, J.; Leinfelder, W.; Sawers, G.; Zinoni, F. Mol. Microbiol.

1991, 5, 515-520.

Initial Reduction Rates (ν0) of H2O2 (3.75 mM) with PhSH (1 mM) in methanol in the presence of various selenium catalysts (0.01 mM)

Catalysts ν0 M min-1

0.55 (0.18)

3.39 (0.37)

3.16 (0.52)

3.83 (0.32)

5.78 (0.79)

28.38 (3.88)

Catalysts ν0 M min-1

36.10 (0.12)

574.01 (23.98)

466.49 (28.26)

Inactive Catalysts

[R, S; R, S] (+)

[S, R; S, R] (-)

GPx-Like Activity of Chiral Ferrocenyl Selenium Derivatives

Strong Se N interaction

Does not favor selenol formation

Thiol exchange occurs

Weak Se N interaction

Favors selenol formation

No thiol exchange

Intramolecular Interaction and Thiol Exchange

Mugesh, G.; Singh, H. B. Chem. Soc. Rev. 2000, 29, 347−357.

Mugesh, G.; Panda, A.; Singh, H. P.; Punekar, N. S.; Butcher, R. J. Chem. Commun. 1998, 2227−2228.

Mugesh, G.; Panda, A. Singh, H. B.; Punekar, N. S.; Butcher, R. J. J. Am. Chem. Soc. 2001, 123, 839−850.

ROOH

ROH

H2O

ESe

ESeOH

ESeSG

GSH

GSH

GSSG

H+

O

O

O

O

Li

n-BuLi

Li

O

BrCH2OH

CH2OH

O

O

SeHCl

Se

O

O

O

O

R

R

NH2

MeCNNH2

HH

Se

N

N

R

Se

N

NH

NaBH4

H

EtOHSe

N

N

R

Se

N

N

R

Ether

Se(dtc)2

R = CH2CH2 and

CH2CH2NHCH2CH2

Selenaazamacrocycles

1) Template free synthesis

2) [2+2] condensation without

recourse to high dilution

3) Good yield

4) Hybrid ligands

Se-Se: 3.808 Å

Se-N(1A): 3.010 Å

Se-N(1B): 3.555

C(1A)-Se-C(1B): 98.03(10)

O

O

O

O

Li

n-BuLi

Li

O

BrCH2OH

CH2OH

O

O

SeHCl

Se

O

O

O

O

R

R

NH2

MeCNNH2

HH

Se

N

N

R

Se

N

NH

NaBH4

H

EtOHSe

N

N

R

Se

N

N

R

Ether

Se(dtc)2

R = CH2CH2 and

CH2CH2NHCH2CH2

Selenaazamacrocycles

NHH

HNNH NHNH N

HN

Se

N

Se

HN

Hg

Hg(PF6)2Se

NH

Se

HNH

NH

NH2

H2NNH2

(CF3COO-)6Se

NH2

Se

H2NH2N

(ii) (CF3COO-)2, (excess), MeOH

(i) Hg(CH3COO)2, NH4PF6, MeOH, reflux, 30 min.

(i)

(ii)

Reactions of Selenaazamacrocycles

Hg-Hg1: 2.5358(8)

Hg- N(1B): 2.468(8)

Se….Se: 11.1962

Se….Hg#1: 5.8185

Singh et al.

Chem. Commun., 143, 2000

Chem. Commun., 322-323 (2004)

Inorg. Chem. 43, 8532-8537 (2004)

J. Chem. Soc. Dalton., Trans., 1203,(1996)

NMe2NMe2Fe

O

N

O

N

Single source precursors for Group 12-16 semiconductors

M(ER)2

M E

Zn S

Cd Se

Hg Te

ME (Binary, Ternary

combinations)Metal

Chalcogenolates

Polymeric

Insoluble

Low volatility

Strategies: a) Use of bulky R groups

b) Adduct formation with neutral ligands

R =, ,

O

NE

-Li

+

O

N

O

N[O]

E M E

O

N

E Hg

MCl2

O

N

O

N

Hg

E

MeOH

O

N

O

N

E

EE = S, Se, and Te

E = S and Se

i) n-BuLi ii) E powder

Zinc, Cadmium and Mercury Chalcogenolates

Mass Spectroscopy

Zn(RSe)2+

m/e = 572

Zn2(RSe)3+

m/e = 890

Cd(RSe)2+

m/e = 619

Cd2(RSe)3+

m/e = 985

Hg(RSe)2+

m/e = 709

(no peak corresponding

to dimer)

M(SeR)2

TGA/TDA

Zn(SeR)2

Cd(SeR)2

Zn(SeR)2

ZnSe + R2Se

CdSe + Se

Hg + R2Se2

~300oC

~300oC

~300oC

[RSeR]+

+ MSe

Monomeric,

hydrocarbon soluble,

Crystalline

O

N

E Zn

O

N

E

E = O, S, Se, Te

P21

Chiral space group

1. Enantiomerically pure, interconversion between (P) and (M) helix

slow at room temperature

2. Thiolato- both pure enantiomers and recemic forms isolated

3. Zinc phenolate- -550C AB quartret

4. Zinc tellurolate- -600C AB pattern resolved

Singh et al.

Polyhedran (Report), 1996, 15, 745

J. Chem. Soc., Dalton Trans., 1996, 461.

Inorg. Chem., 1998, 37, 2663.

Eur. J. Inorg. Chem., 1999, 1229.

J. Organomet. Chem., 1999, 577, 293.

Eur. J. Inorg. Chem., 2001, 669.

24

Macrocycles with multiple sites of Lewis acidity

Important features of metallamacrocycles

1. Catalytic activation of electron rich organic and inorganic

substrates

2. Anion transport

3. Selective molecular recognition

4. Sensors

Important features of mercury metallamacrocycles

1. Due to relativistic effects, capable of exhibiting Metal….Metal

interactions between closed shell ions/atoms

2. Linear geometry leads to large cavities

Metallamacrocycles

25

IR 199Hg NMR

1640 cm-1 -690 ppm

1632 cm-1 -683 ppm

1640 cm-1 -683 ppm

IR 1662 cm-1

199Hg NMR -749 ppm

Significant bond distances Å

Hg(1)-C(1A) 2.112(11)

Hg(1)-C(1B) 2.148(12)

Hg(1)-N(1B) 2.65(2)

Hg(1)-N(1A) 2.70(2)

Hg(1)-Hg(2) 4.992(2)

Significant bond angles (° )

C(1A)-Hg(1)-C(1B) 175.2(7)

C(16A)-Hg(2)-C(16B) 175.1(7)

26

Complexation with Cu(I) ion

IR 1627 cm-1

199Hg NMR

-558 ppm

IR 1640 cm-1

199Hg NMR -690 ppm

ΔE value 0.078 V

-538 ppm

27

Cu1-Hg1 2.92, Cu1-Hg2 2.91 Å

Hg1-Hg1# 3.20 Å

Cu1-N1 2.06, Cu1-N2 2.07 Å

Hg1-Cu1-Hg2 177º

Cu1-Hg2-Hg2# 154.4º

Crystal structure of Cu(I) Complex, showing Hg•••Cu,

heterometallic and Hg•••Hg homometallic d10•••d10 interaction

Covalent radii of

Cu = 1.17 Å and Hg = 1.44 Å

Sum of van der Waal’s radii

Hg = 1.75 + Cu = 1.40 = 3.15 Å

For Hg (1.75 + 1.75) = 3.50 Å Singh et al., Angew. Chem. Int. Ed. 2005, 44, 1715.

28

Selected bond lengths (Å)

and angles (º):

Hg-Hg 3.37

Hg∙∙∙N 2.66

Hg-O 2.07 Å

C-Hg-O 178.49

Hg-O-Hg 109.32º

IR 1622 cm-1

199Hg NMR 1044 ppm

Synthesis of Hydroxo-Bridged Mercury Complex

Singh et al., Organometallics 2010, 29, 4265.

29

Synthesis of novel Pd complex exhibiting

Hg···Pd···Hg interaction (d10-d8-d10)

30

Hg1-Pd 3.1020(3)

Hg2-Pd 3.2337(3)

Hg1-N1A 2.6662(19)

Hg2-N1B 2.647(2)

Pd-N2A 2.1611(18)

Pd-N2B 2.1602(19)

Hg1-Pd-Hg2 162.898(7)

C1A-Hg-Cl1 165.58(7)

C1B-Hg-Cl2 169.14(7)

Helical structure of Pd complex skeleton

Space filling model

Bond length in (Å) and bond angle in (°)

Singh et al., Angew. Chem. Int. Ed. 2009, 48, 1987.

Sagar

Ph.D. Students

1. Pawan K. Khanna (July 1984-1989)

2. N. Sudha (July 1985 - July 1989).

3. S. Kalyan Kumar (Jan 1986 - Dec. 1991).

4. A. Regini (Jan. 1987 - Jan. 1992).

5. K. Rani (Jan. 1988-1993).

6. Rupinder Kaur (July 1991 to Jan. 1996).

7. Saija C. Menon (July 1991 to July 1996)

8. E.V.K. Suresh Kumar (July 1993 to Feb. 1998)

9. G. Mugesh (July 1994 to July 1998)

10. Arunashree Panda (Jan 1995 to Dec. 99)

11. Sanjio, S. Zade, (Dec. 1999 - 2004)

12. K. Kandasamy, (July 1999 - 2004)

13. Snigdha Panda, (July 1999 - 2004)

14. Sangit Kumar, (July 1999 -2004)

15. Upali Patel, (July 2000-2005)

16. Sagar Sharma (July 2004-2009 Dec)

17. Kriti Srivastava (Jan 2005-2010 Jan )

18. K. Selvakumar (Jan 2005- May 2010)

19. Tapash Chakraborty (Jan 2005-May 2010)

20. Vijay Pal Singh (Jan 2006-May 2011)

21. Sudesh T. Manjare (July 2006-2011)

22. Prakul Rakesh (July 2006-2012)

23. Poonam Shah (July 2007-)

24. Shikha Das (July 2009-)

25. Sangeeta Yadav (July 2010-)

26. Anand Kumar Gupta (July 2010-)

27. Satheeshkumar (July 2011-)

28. Varsha Tuteja (July 2011-)

29. Venkatashwaran (July 2011-)

30. R. Saravanan (July 2012-)

31. S. Aravindhan (July 2012-)

AcknowledgementPost-Doctoral Fellows /Research Assistants

1. Dr. S. Kalyankumar (1991)

2. Dr. Jai Deo Singh (1990-93)

3. Dr. N. Sudha (1994)

4. Dr. Saija C. Menon (1996-97)

5. Dr. G. Mugesh (1998-1999)

6. Dr. Arunashree Panda (Feb.2000-July 2000)

7. Dr. Santosh Kumar Tripathi (July 2001-2004)

8. Sandeep Apte (July 1999-May 2000)

9. Anna Mukharjee (Nov.1999-May 2000)

10. Urmila Patil (July 1999-May 2000)

11. Dr. Rajesh Baligar (August 2005- June 2007)

12. Goutom Mukherjee (May 2007-Dec 2007)

13. Dr. Sagar Sharma (March 2010-Sep 2010)

14. Dr. Kriti Srivastava (Sep 2010- Feb 2011)

15. Dr. K. Selvakumar (April 2010-October 2011)

16. Dr. Sudesh Manjare (October 2011- 2012)

17. Dr. Puspendra Singh (August 10, 2010-)

18. Dr Ninad Ghavale (May 2011-)

19. Dr. Kandasamy Gopal (October 2011-)

Funding Agencies : DST, CSIR, BRNS, DRDO

Prof. R. J. Butcher Prof. R. B. Sunoj

Dr. G. Wolmershauser Prof. N. S. Punekar

Dr. R. P. Patel Prof. S. Durani

Synthesis and Reactivity of First Room Temperature Stable

Organoselenenyl(II) azides

Klapötke and coworkers by employing intramolecular coordination reported the isolation

of first organoselenenyl(II) azide, stable at 0 C.

First room temperature stable organoselenenyl(II) azide by employing intramolecular

coordination and steric hindrance.

[M + Na]+ peak at m/z 575.1342 in HRMS

Klapötke and coworkers, J. Am. Chem. Soc., 2004, 126, 710

N

Se

N3

r.t, 2 h, CuP(OEt)3I

THF: H2O (2:1)Se

N

O

NN

N

N

O

Se

N3

B3LYP/6-31+G(d) level

Kriti

Entry Se−N (Å) E Se…N/O

(Kcal/mol)

1 2.421 23.66

2 2.261 41.58

3 2.342 32.15

4 2.180 54.41

5 2.265 43.16

6 2.377 20.64

N

Se

N3

1 2 3

4 5 6

Singh and coworkers, Dalton Trans., (2010) 39, 10137.

First Structural Characterization of a Selenenyl selenocyanate

(RSeSeCN Unsymmetrical diselenide)

77Se NMR 888, 11513C NMR 15 peak

FT-IR 1599 ( C=N), 2110 ( C≡N)

HRMS [C20H22N2Se2K+ (MK+)

calcd: 488.9750, Found: 488.9773.

N•••Se1 2.116(2)

Se1-Se2 2.6069(4)

Se1-Se2-C20 101.9(2)

C1-Se1-Se2 97.6(8)

van der Waals radii (Å)

N 1.55

Se 1.90 3.45

Prakul

H2N OH

O SOCl2

MeOH H3N O

O

Me

Cl

BrCOCH2Br

Et3N, DCM HN O

O

Me

H2C

Br

O

Na2Se2

NH

OO

Me

CH2

O

Se NH

O O

Me

CH2

O

Se

NHO

O

Me

O

Se

THF,

-72 oC

+

Molecular Structure

77Se = 371 ppm 77Se = 262 ppm

First Structure of Selenocysteine

m.p. = 91 oC

Yield = 40 %

m.p. = 75 oC

Yield = 80 %

77Se = 295 ppm

Stocking et al. J. Chem. Soc., Perkin Trans. 1, 1997, 25, 2443

Te2∙∙∙O7 2.895 Å

Te2∙∙∙O10 2.961 Å Molecular structure

Red Liquid

77Se = 260 ppm

Synthesis of Tellurocysteine derivatives ?

125Te = 814 ppm125Te = 589 ppm

Yield = 70 %

Yield = 80 %

Yield = 40 %

m.p. = 166 oC

m.p. = 177 oC

Glutathione Peroxidase (GPx)

Cytosolic GPx (cGPx) – uses GSH as co-substrate

Reduction of hydrogen peroxides and organic peroxides

ROOH + 2GSH ROH + GSSG + H2OGPx

Tetramer of four identical subunits; each subunit contains a

selenocysteine residue

Catalytic triad – SeCys, Gln, Trp - Selenolate is highly stabilized

Se

N

SeCys H2N

O

Trp148

.....

.....

+HH

Gln70

ROOH

ROH

H2O

ESe

ESeOH

ESeSG

GSH

GSH

GSSG

H+

Epp et al. Eur. J. Biochem. 1983, 133, 51

O

Se

N Ph

O

Se

N Ph

NO2

OH

SeNAc

SeN

O

Ph

O

Se

N Me

N

Me

c-C6H11

Se

N

Se

NMe2

Se

H

Cl-

Se

O

O

)2

)2

)2

+

GPX Mimics

Ebselen

N

Se

O

(1) (2) E = Se; (3) E = Te

2E)

2E)

(4) E = Se; (5) E = Te

2E)

(6) E = Se; (7) E = Te

E)Fe2

(8) E = Se; (9) E = Te

N

E)2

(10) E = Se; (11) E = Te (12) E = Se; (13) E = Te

O

N

E)2

E)

NMe2

2

(18) E = Se; (19) E = Te(14) R = Et, R' = H; E = Se;

(15) R = Et, R' = H; E = Te;

(16) R = R' = H; E = Se

(17) R = R' = H; E = Te

R'R

O

N

E)2

O

PhH

(20) E = Se; (21) E = Te

2E)

N

2E)

(22) E = Se; (23) E = Te

H

NMe2

E)

Me

Fe2

(24) [R,S;S,R] (+); E = Se

(25) [R,S;S,R] (+); E = Te

Singh et al.Chem. Soc. Rev. 2000, 29, 347

Proc. Natl. Acad. Sci. 2000, 70, 207

J. Am. Chem. Soc. 2001, 123, 839-850

Chem. Commun. 2000, 143

Organometallics 2002, 21, 884

Organochalcogen Compounds As a GPx Mimics

Table: Initial reduction rates (v0)[a] of H2O2 (3.75 mM) with PhSH (1 mM)

in the presence of various dichalcogenide catalysts (0.1 mM).

[a]Obtained by Lineweaver-Burk Plots. [b]Standard deviations are shown in parentheses.[C]Inactive at lower concentration.9 [d]Since the reduction rate was too fast to be determined

at 0.1 mM concentration range, 0.01 mM was used for the experiments.9 [e]decomposed

entry catalyst

(E = Se)

v0[b] M.min-1 entry catalyst

(E = Te)

v0[b] M.min-1

a 2 24.08(1.04) b 3 59.52(3.58)

c 4 53.21(5.81) d 5 142.97(5.17)

e 6 31.48(3.07) f 7 70.47(5.40)

g 8 33.92(0.37) h 9 77.61(6.08)

i 10 124.02(7.89) j 11 1629.56(5.67)

k 12c 28.87(1.72) l 13 135.09(10.04)

m 14c 18.53(1.32) n 15 109.38(6.95)

o 16 41.64(1.48) p 17 -e

q 18c 45.34(2.81) r 19 239.00(8.99)

s 20 3.52(0.87) t 21 9.83(1.82)

u 22 inactive v 23 inactive

w 24 574.01 (23.98)d x 25 -e

Organochalcogens with two coordinating heteroatoms

..

Plausible mechanism

Br2

CHO

C

SeO H

HO

CHO

CHO

Se)2

CHO

CHO

SeBr

..

Se

O

O

CHO

OHC

C

Se

OH

Br

8

SeO

CHOOHC Se

O

O

-Br-

H2O

H+-

-

CHO

CHO

Se2

)

CHO

CHO

BrNa2Se2

THF, Reflux, 4h Br2Se

O

O

OHCCHO

SeO

NMe2

Se )2

M min-1

Se OOHC

O

SeOCHO

M min-1

CHO

CHO

Se2

M min-1

)

Space Group: P-1

R value: 0.0349

C7A-O-C7B: 113.12

Se1A…O2A: 2.6042 Å

Se1B…O1B: 2.4647 Å

Se-O bond containing compounds as a GPx mimics

OH OLi

LiTHF

OH

Se

OLi

SeLi

OH

Se

i. n-BuLi

ii. TMEDA Penatne

Se powder

Se(dtc)2

2 2

[O], H2O

Monoclinic

Space group = P2(1)/n

Se(1)-C(11) = 1.934(3) Å

Se(1)-Se(2) = 2.3220(6) Å

C(11)-Se(1)-Se(2) = 101.99(9)o

C(21)-Se(2)-Se(1) = 104.40(9)o

C(12)-C(11)-Se(1) = 116.6(2)o

Orthorhombic

Space group: Pbca

Se-O(1) = 1.794(5) Å

Se-O(2) = 1.630(5) Å

Se-C(1) = 1.939(4) Å

O(2)-Se-O(1) = 105.1(3)o

C(1)-Se=O(2) = 101.4(2)o

C(1)-Se-O(1) = 86.5(3)o

OH

Se Br

OH

Se

O

TBHP

OH

Se

TBHP

SeO

O

OH

SeO

OH

2

i. NaBH4

ii.

[2, 3] shift

-

TBHP

Seleninate Esters:

Se

O

O

OH

Se

H2O2

AcOH2

Monoclinic

Space group: C2/c

Se-O(1) = 1.922(3) Å

O(1a)-H(2) = 2.4476Å

C(2)-H(2)-O(1a) = 111.25()o

O(1)-Se-O(1a) = 174.41(13)

C(1)-Se-C(1a) = 101.74(15)o

C(1)-Se-O(1a) = 92.75(11)o

C(7)-O(1)-Se-O(1a) = -34.68(10)o

C(1)-Se-C(1a)-C(2a) = -97.95(3)o

C(1a)-Se-O(1)-C(7) = -85.22(2)o

Monoclinic

Space Group: P21/c

Se-O1A: 1.9747(14)

O1A-Se-O1B: 172.85(6)

C1A-Se-C1B: 101.42(8)

O

O

Se

[O]

SeO

O

O

O

Se

O

O

Se

O

O

O

OO

O

Monoclinic spacegroup: C2/c

Acta Chem. Scand. 27 (1973) 2219

Monoclinic P21, Optically pure

Chirality 12 (2000) 71

t-Bu

CONHR

E

N

O

R

THFt-Bu

CONHR

CONHR

Br

t-Bu

CONHR

CONHR

SeCH2OCH3

THF

t-Bu

COOH

COOH

Br

t-Bu

CONHR

CONHR

Se

1 2 R = Ph3 R = Me4 R = iPr

5 R = Ph, E = Se6 R = Me, E = Se7 R = iPr, E = Se8 R = Ph, E = S9 R = Me, E = S10 R = Me, E =Te

11 R = Ph12 R = Me13 R = iPr

5, 6, 7

i. SOCl2

ii. RNH2

Li2Se2

i. n-BuLi

ii. (CH3OCH2)2Se2

Li2Se2

)2

Br2

-CH3OCH2Br

-HBr

Synthesis of new Ebselen analogues with intramolecular coordination

Space Group: I2/a

R value: 0.0349

Se1 O2: 2.435 Å

Se1 N1: 1.916 Å

Se1-N1-C7: 115.88

Se1-N1-C8: 119.99

C7-N2-C8: 124.65

51

Theory of closed shell metal-metal (d10-d10) interaction

It is a kind of attractive interaction between closed shell metal ions.

The interaction energy increases down the group i.e.; for heavy metals.

Gold-gold interaction (aurophilicity) is the best example for d10-d10 interaction

The aurophilic bond strength is about 7-12 kcal/mol (comparable

to the strength of a hydrogen bond).

This interaction can be explained by the theory of relativity.

Pyykkö, P; Mendizabal, F. Inorg. Chem. -

Pyykkö, P. Angew. Chem. Int. Ed. , 4412-4456

52

Heavy metals have larger nuclear charge

Heisenberg uncertainty principleVelocity increases (comparable to C);

for gold V1s 0.6C.

Rest mass of the core electrons increases as per equation

mv = m0 /[1-V2/C2]0.5; mv and mo are the moving mass and rest mass

of the electron.

Results in significantly more kinetic energy to the particle

Size of Inner s and p orbitals shrinks

To maintain orthogonality, the s- and p-orbitals of higher quantum

number also contract and shield the nucleus more

d and f orbital expand radially and increase in energy

d and f orbital are therefore more destabilized and

polarisable

Relativistic effect

Core electrons are subjected to greater electrostatic field hence Volume

decreases.

53

Synthesis of (o-formylphenyl)mercury, precursor for the

synthesis of mercuraaza macrocycle

IR 3122 cm-1 1662 cm-1

199Hg NMR -689 ppm -749 ppm

Upali

E

O

N

E = S/Se

E

O

N

Cd

TOPO/TOP2700C

CdS/CdSe + R2S/R2Se

Hexagonal CdS

Particle size calculated Powder X-ray Diffraction Pattern of CdS

from Scherrer’s Equation

For CdS = ~5-7 nm

Hexagonal CdSe

Particle size calculated Powder X-ray and Electron Diffraction

from Scherrer’s Equation Pattern of CdSe

For CdSe = ~10-12 nm

SEM photograph of CdSe

Particle size 4-5 microns

Preparation of CdS and CdSe nanoparticles

TEM micrograph of CdSe

Particle size 200-250 nm

Te Hg

O

N

TeLi Te

O

N

O

N

O

N

E Hg

ELi

2

2

i) n-BuLi, Et2O, Te0, 0

oC, 2 h ii) [O]/H2O iii) Hg, MeOH, rt, 24 h.

(i) (ii)

(iii)

(i) (ii)

(iii)

(1) (2) (3)

(4)

(5) (6) (7)

(8)

2

O

N

O

N

O

N

O

N

E2

E = Se/Te

Synthesis of mercury chalcogenolates

Crystal structure of mercury selenolate

125Te NMR of mercury

tellurolate