Indian Journal of Chemistry

Sect. A: Inorganic, Bio-inorganic, Physical, Theoretical & Analytical
CODEN: ICACEC; ISSN: 0376-4710 (Print), 0975-0975 (Online)

http://www.niscair.res.in; http://nopr.niscair.res.in

Total visitors: 11124 since 04-10-2011

 

Special Issue Dedicated to Acharya P C Ray

 

VOLUME 50A

NUMBER 9-10

SEPT-OCT 2011

Cover Page

Title

Preface

CONTENTS

 

1239

 

Synthesis, characterization and spectroscopy of composites of graphene with CdSe and CdS nanoparticles

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Kota Moses, L S Panchakarla,
H S S Ramakrishna Matte, Bolla Govindarao
& C N R Rao*

 

 

 

 

Nanocomposites of few-layer graphene with nanoparticles of CdSe and CdS have been synthesized and characterized. Electronic interaction between nanoparticles and graphene has been examined by Raman and photoluminescence spectroscopies.

 

 

 

 

 

1248

 

Discrete monomeric and chloride-bridged dimeric and 1D coordination polymeric mercury(II) complexes of a class of pyridyl-pyrazole ligands with variable denticity and flexibility

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Saleem Javed, V Balamurugan, Wilson Jacob,
Anuj Kumar Sharma & Rabindranath Mukherjee*

 

 

 

 

Synthesis and structural characterization of two discrete and a 1D coordination polymeric HgII complexes of pyridyl-pyrazole ligands have been achieved.

 

 

 

 

 

1257

 

From molecular to micro structure via nanostructure of a nickel(II) dithiolene complex

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ameerunisha Begum, Manav Saxena,
Sumit K Sonkar & Sabyasachi Sarkar*

 

 

 

 

The molecular shape of a metal-ligand complex,
[PPh4][NiII(L2-)(L1-
·)] (L = 1,2-dicarbomethoxyethylene dithiolate), viz., rectangular and hexagonal prismatic, are the repeating motifs/patterns manifested in lattice packing of the complex that extend to the nano domain.

 

 

 

1263

 

Synthesis of intramolecularly coordinated cyclic selenenate/thioselenenate esters and their glutathione peroxidase-like activity

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Vijay P Singh, Harkesh B Singh* & Ray J Butcher

 

 

 

 

The thionation reaction of the seleninate ester 26 affords thioselenenate ester whereas the seleninate ester 20, under similar conditions, yields diselenide.

 

 

 

 

 

 

1273

 

Isolation and characterization of two isomeric arylamine substituted triazinium salts. Studies of intramolecular charge-transfer and electrochromic properties

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mominul Sinan, Pradip Ghosh &
Sreebrata Goswami*

 

 

 

 

Reaction of 9,10-diaza-4a-azonia-phenanthrene perchlorate ([1]ClO4) with para-toludine in acetonitrile affords two isomeric compounds, the red coloured para isomer ([2a]ClO4) and blue coloured ortho isomer ([2b]ClO4).

 

 

1281

 

An eight-connected metal organic framework based on Cu5clusters: Synthesis, structure, magnetic and catalytic properties

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Debajit Sarma & Srinivasan Natarajan*

 

 

 

 

A new meta-organic framework compound,
[Cu53-OH)2(H2O)6{(NO2)-C6H3-(COO)2}4].5H2O, with pentameric Cu5 cluster is synthesized. The compound forms a pillared
CdCl2-like structure. The syntheses, structure, magnetic and catalytic studies of the obtained phases are reported.

 

 

1290

 

Cyclometalated Ir(III) complexes containing ancillary pyrazole-based ligands

 

 

 

 

 

 

 

 

 

 

 

 

Tanima Hajra, Soumya Ghosh, Jitendra K Bera*
& Vadapalli Chandrasekhar*

 

 

 

 

Neutral mononuclear cyclometalated Ir(ppy)2 complexes with a variety of pyrazole-based ancillary ligands have been synthesised, characterised and their photophysical properties studied.

 

 

1298

 

A rhodamine-piperazine conjugate as a fluorogenic sensor for mercury(II) ion in aqueous
ethanol medium

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Shubhra Bikash Maity & Parimal K Bharadwaj*

 

 

 

 

A new bis-rhodamine piperazine conjugate that exhibits high fluorescence specifically in presence of Hg2+ ion in aqueous ethanol has been synthesized.

 

 

 

 

1303

 

Synthesis and characterization of some gold(I)-thiolate complexes having N-methylimidazole moiety

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Krishna P Bhabak & Govindasamy Mugesh*

 

 

 

 

Therapeutic gold(I) drugs interact with the antithyroid drug methimazole to produce gold(I)-thiolate complexes. These gold(I)-thiolates undergo extensive thiol exchange reactions in the presence of various nucleophiles.

 

 

 

 

 

1308

 

Ag@Pd core-shell nanoparticles

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Deepa Jose & Balaji R Jagirdar*

 

 

 

 

 

 

 

1318

 

Synthesis and structural studies of copper(II) and nickel(II) complexes containing 4,5-diazafluoren-9-one and pseudohalides: Metal ion directed isomer preference

 

 

 

 

 

 

 

 

 

 

 

B Kishore Babu, S M Elahi, T Krishna Chary &
M V Rajasekharan*

 

 

 

 

Metal ion directs the isomer preference between cis- and
trans-octahedral coordination for a ligand with long chelate bite.

 

 

 

 

 

1324

 

Ruthenium complexes of two different non-innocent ligands. Investigation of electronic structural aspects by experimental and DFT analysis

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Tanaya Kundu, Abhishek Dutta Chowdhury, Biswajit Laha, Shaikh M Mobin &
Goutam Kumar Lahiri*

 

 

 

 

The oxidized forms of non-innocent ligands Q (o-benzoquinone-diimine) and non-planar tppz (2,3,5,6-tetrakis(2-pyridyl)pyrazine) in (1) and (2) undergo successive close-by multiple reductions besides metal based oxidation(s). The mixed valent RuIIRuIII state in (2+) exhibits Kc~102, revealing a valence localized class II situation.

 

 

 

 

1334

 

Synthesis and structural studies of cobalt(III) complexes of 5-methyl-3-formylpyrazole-N(4)-ethyl/ dimethyl thiosemicarbazone and nickel(II)
complex of 2-S-methyl-6-methyl-4-formylpyrimidine-N(4)-ethyl thiosemicarbazone

 

 

 

 

 

 

 

 

 

Atanu Janaa, Saugata Konar, Sangita Ray,
Shie-Ming Peng, G H Lee, Ray J Butcher,
Tian-Huey Lu,
Anil Kumar Barik, Sachindranath Pal & Susanta Kumar Kar*

 

 

 

 

Two new cobalt(III) complexes of pyrazole derived thiosemicarbazones and one nickel(II) complex of a pyrimidine derived thiosemicarbazone are studied.

 

 

 

1343

 

Recognition of nitrates in a discrete dimeric capsular assembly of a triamide half-capsule

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

M Arunachalam & Pradyut Ghosh*

 

 

 

 

A bowl-shaped new tripodal amide receptor with p-cyanobenzoyl terminals shows formation of nitrate capsules whereas acetate shows a non-capsular aggregation.

 

 

 

1350

 

A fluoro-bridged dinuclear nickel(II) compound from tetrafluoroborate precursor: Making sense of a serendipitous reaction

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Raj K Das, Tapas Ghatak, Ramesh C Samanta & Jitendra K Bera*

 

 

 

 

A fluoro-bridged, hydrogen-bond stabilized dinuclear nickel(II) compound is isolated from the reaction of [Ni(CH3CN)6](BF4)2 with amide-linked ferrocene-naphthyridine hybrid ligand.

 

 

 

1356

 

Incorporation of lead(II) by copper(II)-salicylaldimine type ligand complexes: Cation–π interactions in controlling the distortion of coordination geometry around lead(II)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Saptarshi Biswas & Ashutosh Ghosh*

 

 

 

 

Synthesis and structural characterization of two trinuclear copper(II)-lead(II) complexes show that the lead ion can easily be incorporated by copper-salicylaldimine type “ligand complex” and the distortion of geometry around Pb(II) is controlled by cation–π interactions.

 

 

 

1363

 

Synthesis and structural characterization of an open cage dithiatungstaborane [(CpW)2B4H4S2] cluster

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Rajendra Singh Dhayal, Joseph Ponniah S, Satyanarayan Sahoo & Sundargopal Ghosh*

 

 

 

 

Reaction of [Cp*MoCl4] or [CpWCl4] with excess of [LiBH4.thf] followed by thermolysis with excess of [HS(CH2)nSH] (n = 2 or 3) leads to the formation of [(Cp*Mo)2B4H4S2] or [(CpW)2B4H4S2] respectively.

 

 

 

1369

 

Copper(II) complexes of 13–membered amide-based macrocyclic ligands: Effect of electronic substituents on redox properties

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Sushil Kumar & Rajeev Gupta*

 

 

 

 

Copper(II) complexes in a set of amide-based 13-membered macrocyclic ligands are reported. The electron-donating and electron-withdrawing substituents present on the macrocyclic framework alter the redox properties of the compounds considerably.

 

 

 

 

 

1380

 

Heterogeneous Stille and Sonogashira cross-coupling reactions over palladium anchored mesoporous silica catalyst

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Susmita Bhunia & Subratanath Koner*

 

 

 

 

Palladium anchored chemically modified MCM-41 catalyst has been employed in Stille and Sonogashira cross-coupling reactions in heterogeneous condition. The ligand-free reaction affords good to excellent yield of the desired products. The highly efficient solid catalyst can be recycled several times without any loss of activity.

 

 

 

 

1388

 

Aminosilicate sol-gel embedded core-shell
(TiO2-Au)nps nanomaterials modified electrode for the electrochemical detection of nitric oxide

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Alagarsamy Pandikumar & Ramasamy Ramaraj*

 

 

 

 

The glassy carbon electrode modified with core-shell EDAS/(TiO2-Au)nps has been used as a nitric oxide sensor. The GC/EDAS(TiO2-Au)nps modified electrode shows good electrochemical and electrocatalytic properties towards NO with the lowest detection limit of  1 μM.

 

 

1394

 

Synthesis and reactivity of cobalt complexes derived from tris(2-pyridylthio)methane ligand: Structural characterization of cobalt(III) complexes containing cobalt–carbon bond

 

 

 

 

 

 

 

 

 

 

 

 

Partha Halder & Tapan Kanti Paine*

 

 

 

 

A low-spin cobalt(II) complex of tris(2-pyridylthio)methane ligand reacts with molecular oxygen to generate, depending upon the reaction conditions, two different cobalt(III) complexes containing the cobalt–carbon bond.

 

 

 

1403

 

Synthesis, structure and electrochemical properties of some thiosemicarbazone complexes of ruthenium

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Sayanti Datta, Michael G B Drew &
Samaresh Bhattacharya*

 

 

 

 

Thiosemicarbazones of salicylaldehyde, 2-hydroxyacetophenone and 2-hydroxynaphthaldehyde react with [Ru(dmso)4Cl2] to afford a family of three dimeric complexes, where these ligands display two interestingly different modes of binding, viz., O,N,S-mode with additional bridging from the sulfur-site and N,S-mode associated with conformational change across the imine fragment.

 

 

 

 

1410

 

Synthesis and structural characterization of potassium coordination polymers based on a copper-bis(dithiolato) complex: Role of coordinating solvents and counter cation

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ramababu Bolligarla, Bharat Kumar Tripuramallu, Vudagandla Sreenivasulu & Samar K Das*

 

 

 

 

Synthesis of two new potassium based coordination polymers (1) and (2) of copper bis(dithiolene) complex, [CuIII(btdt)2] ({btdt}2– = 2,1,3-benzenethiadiazole-5,6-dithiolate), has been described. Interestingly, extended networks of the compounds (1) and (2) in the solid state show 3D and 2D metal-coordination polymers respectively, which are obtained simply by varying the coordinated solvents in the recrystallization processes.

 

 

 

1418

 

Osmium(II) mixed-chelate derived from
imidazole 4,5-bis(benzimidazole) and 2,2
¢-bipyridine as multichannel sensor for anions: Synthesis, structural characterization and binding studies

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Debasish Saha, Shyamal Das, Dinesh Maity &
Sujoy Baitalik*

 

 

 

 

The monometallic Os(II) mixed-chelate derived from
imidazole 4,5-bis(benzimidazole) and 2, 2
¢-bipyridine can act as multichannel sensor for F-, AcO- and H2PO4- ions in solution.

 

 

 

 

1429

 

Syntheses, structures and molecular properties of two mononuclear cobalt(III) halide complexes containing a tetradentate N-donor Schiff base

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Sumitava Khan, Kishalay Bhar, Subhasis Roy, Krishnakumar Ramachandran &
Barindra Kumar Ghosh*

 

 

 

 

Syntheses, molecular and crystalline architectures and properties of two hexacoordinated mononuclear compounds,
trans-[Co(L)X2]ClO4 [L = N,N
¢-(bis(pyridine-2-yl)benzylidine)-1,2-ethanediamine; X = Cl, Br] are described.

 

 

 

1436

 

Models for photosynthetic reaction center: Synthesis, structure and electrochemical properties of a cofacial di-palladium bisporphyrin

 

 

 

 

 

 

 

 

 

Arvind Chaudhary, Ranjan Patra &
Sankar Prasad Rath*

 

 

 

 

 

 

 

1443

 

Trans-dichlorobis(N-p-tolylpyridin-2-amine)palladium(II): Synthesis, structure, fluorescence features and DNA binding

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Suman Kundu, Suvendu Maity, Ranjan Bhadra & Prasanta Ghosh*

 

 

 

 

Synthesis, structure, fluorescence features and DNA binding
of trans-dichlorobis(N-p-tolylpyridin-2-amine)palladium(II) are reported

 

 

 

 

1450

 

Ferromagnetic vs antiferromagnetic coupling in structurally analogous binuclear complexes based on salen type ligand

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Rampal Pandey, Joan Ribas, Montserrat Corbella & Daya Shankar Pandey*

 

 

 

 

Dinuclear complexes of Co(II), Cu(II), Ni(II), Zn(II) and Cd(II) containing the Schiff base ligand N,N′-bis(2-hydroxybenzilidene)-2,4,6-trimethylbenzene-1,3-diamine have been investigated. Structure of the cobalt complex, [Co(C23H18N2O2)]2,
has been determined crystallographically. Variable
temperature magnetic susceptibility measurements on Co(II)
and Cu(II) complexes reveal that the former
displays antiferromagnetic (J = -0.21
± 0.1 cm-1) and the latter ferromagnetic (J = +1.23 ± 0.1 cm-1) coupling.

 

 

 

1457

 

Density functional theory calculations on biological S-transfer: Insight into the mechanism of rhodanese

 

 

 

 

 

 

 

 

 

 

 

Subal Dey & Abhishek Dey*

 

 

 

 

Biological sulfur transfer (S-transfer) is a key step in the synthesis of metabolites, CN- detoxification and assembly of iron-sulfur clusters. Computational results addressing the thermodynamics of the S-transfer reactions from thiosulfate (natural S-donor) to HCN and thiol are presented.

 

 

 

1463

 

Zinc and cadmium complexes of a Schiff base
ligand derived from diaminomaleonitrile

and salicylaldehyde: Syntheses, characterization, photoluminescence properties and DFT study

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Averi Guha, Jaydeep Adhikary, Tapan Kumar Mondal & Debasis Das*

 

 

 

 

Zinc and cadmium complexes of a Schiff base ligand derived from diaminomaleonitrile and salicylaldehyde have been synthesized. A thorough DFT study has been performed to understand the origin of their electronic and luminescence properties.

 

 

 

 

Authors for correspondence are indicated by (*)

 

 

 

 

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1239-1247

 

Synthesis, characterization and spectroscopy of composites of graphene with
CdSe and CdS nanoparticles

Kota Mosesa, L S Panchakarlab, H S S Ramakrishna Matteb, Bolla Govindaraob & C N R Raoa, b, *

aMaterials Research Centre, Indian Institute of Science, Bangalore 560 012, India

 bChemistry and Physics of Materials Unit, International Centre for Materials Science and CSIR Centre of Excellence in Chemistry, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur PO, Bangalore 560 064, India

Email: cnrrao@jncasr.ac.in

Received 31 May 2011; accepted 7 June 2011

Nanocomposites of few-layer graphene with nanoparticles of CdSe and CdS have been synthesized by two different methods, one involving ultrasonication of a mixture of graphene and the chalcogenide nanoparticles, and another involving assembly at the organic-aqueous interface. The nanocomposites have been examined by electron microscopy, electronic absorption and photoluminescence spectroscopies as well as Raman spectroscopy. Electron microscopy reveals that the nanoparticles are dispersed on the graphene surface. Raman spectra show the presence of definitive electronic interaction between the nanoparticles and graphene depending on the capping agent. Photoluminescence spectra are markedly influenced by the interaction of the nanoparticles with the graphene surface, depending on the capping agent.

Keywords: Nanocomposites, Graphene, Chalcogenide nanoparticles, Liquid-liquid interface, Raman spectroscopy

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1248-1256

 

Discrete monomeric and chloride-bridged dimeric and 1D coordination polymeric mercury(II) complexes of a class of pyridyl-pyrazole ligands with
variable denticity and flexibility

Saleem Javed, V Balamurugan, Wilson Jacob, Anuj Kumar Sharma & Rabindranath Mukherjee*

Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208 016, India

Email: rnm@iitk.ac.in

Received 30 May 2011; accepted 21 June 2011

Using a class of pyridyl-pyrazole ligands with variable denticity and flexibility, i. e., 1-benzyl-[3-(2′-pyridyl)]pyrazole (L10), 2-[3-(2′-pyridyl)pyrazol-1-ylmethyl]pyridine (L5) and 2,6-bis(pyrazol-1-ylmethyl)pyridine (L6), three new mercury(II) complexes – two discrete [(L10)HgII(μ–Cl)Cl]2 (1) and [(L5)HgIICl2] (2) and a coordination polymeric [(L6)HgIICl2]·HgCl2 (3), have been synthesized and structurally characterized. In complex (1) one of the chlorides from each [(L10)HgIICl2] unit acts as a bridge, affording a dichloro-bridged mercury(II) complex with slightly distorted square-pyramidal HgN2Cl3 coordination sphere. The structure of complex (2) reveals an almost ideal square-pyramidal HgN3Cl2 coordination sphere. Complex (3) has N3Cl2 distorted square-pyramidal coordination around HgII ion with coordination by L6 (facial mode) and two Cl ions. Notably, in complex (3) one HgCl2 molecule is present with each [(L6)HgIICl2] unit. Due to weak interaction by HgII-coordinated Cl ion of “[(L6)HgIICl2]” unit to HgCl2, complex (3) is a coordination polymer. Analysis of crystal packing diagram of complexes (1)–(3) reveals occurrence of a variety of non-covalent (π–π, C–Hπ and C–H...Cl) interactions, which play significant role in generating supramolecular architectures of varied topology.

Keywords:   Coordination polymers, Pyridyl-pyrazole ligands, Bidentate ligands, Tridentate ligands, Crystal structures, Non-covalent interactions, Emission spectra, Mercury

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1257-1262

 

From molecular to micro structure via nanostructure of
a nickel(II) dithiolene complex

Ameerunisha Begum, Manav Saxena, Sumit K Sonkar & Sabyasachi Sarkar*

Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208 016, Uttar Pradesh, India

Email: abya@iitk.ac.in

Received 6 May 2011; revised and accepted 1 July 2011

The nanocrystal structure of a hetero-polyatomic metal-ligand complex, [PPh4][NiII(L2−)(L1−·)], (1)
(L = 1,2-dicarbomethoxyethylene dithiolate) has been arrived at from its molecular structure obtained by X-ray crystallography. The complex (1) exhibits dimorphism, existing in two crystal habits at the micro level, viz., rectangular prismatic and hexagonal. Rectangular or hexagonal repeating motifs manifest in the lattice packing of the two crystal structures of (1) in two different solvents which extend up to nano dimension and result in nano sized rectangular and hexagonal prismatic crystals. This provides major clues to understand the shapes of hetero-poly atomic nanocrystals at the molecular level.

Keywords: Coordination chemistry, Dimorphism, Nanocrystals, Crystal structure, Rectangular shape, Hexagonal shape, Nickel

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1263-1272

 

Synthesis of intramolecularly coordinated cyclic selenenate/thioselenenate
esters and their glutathione peroxidase-like activity

Vijay P Singha, Harkesh B Singha, * & Ray J Butcherb

aDepartment of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India

Email: chhbsia@chem.iitb.ac.in

bDepartment of Chemistry, Howard University, Washington DC 20059, USA

Received 13 April 2011; revised and accepted 24 June 2011

The syntheses and characterization of selenenate esters, thioselenenate ester and related derivatives are described. The reactions of n-butyl-4-tert-2,6-di(formyl)phenyl selenide (23) or bis(2,6-diformyl-4-tert-butylphenyl)diselenide (24) with bromine affords a new selenenate ester, 5-tert-butyl-7-(formyl)benzoxaselenol-3-one (25), stabilized by ortho-formyl group along with 3,3′-oxybis(5-tert-butyl-3H-benzo[c][1,2]oxoselenole-7-carbaldehyde) (16). Oxidation of (25) with H2O2 gives
5-tert-butyl-7-(carboxylic)benzoxaselenol-3-one-Se-oxide (26). However, the direct oxidation of (23) with H2O2 affords
5-tert-
butyl-7-(butylcarboxylate)benzoxaselenol-3-one (27). The synthesis of 5-tert-butyl-7-(methylcarboxylate) benzothia-
selenol-3-one
(28) has been accomplished by the reaction of (26) with thionyl chloride (SOCl2) with a catalytic amount of
N, N-dimethylformamide. Attempted thionation of 7-nitro-1,2-benzisoselenole(3H)-Se-oxide (20) leads to the isolation of bis(2-chloromethyl-6-nitrophenyl)diselenide (29). The presence of intramolecular secondary Se···O interactions in all the esters is confirmed by single crystal X-ray diffraction studies and computational studies. Glutathione peroxidase-like activity of (16), (25)-(29) has been determined by the coupled reductase assay.

Keywords: Coordination chemistry, Cyclic compounds, Selenenate esters, Thioselenenate esters, Thionation,
GPx-like activity, Intramolecular interactions, Secondary interactions

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1273-1280

 

Isolation and characterization of two isomeric arylamine substituted
triazinium salts. Studies of intramolecular charge-transfer and
electrochromic properties

Mominul Sinan, Pradip Ghosh & Sreebrata Goswami*

Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Kolkata 700 032, India

Email: icsg@iacs.res.in

Received 11 May 2011; revised and accepted 24 June 2011

Reaction of 9,10-diaza-4a-azonia-phenanthrene perchlorate ([1]ClO4) with para-toludine in acetonitrile at room temperature affords isomeric triazinium compounds (para isomer, [2a]ClO4, 6-p-tolylamino-9,10-diaza-4a-azonia-phenanthrene perchlorate and ortho isomer, [2b]ClO4, 8-p-tolylamino-9,10-diaza-4a-azonia-phenanthrene perchlorate) in moderate yields. X-ray structures of the compounds are reported. The isolated compounds have been characterized by different spectroscopic techniques. The compounds belong to the category of ‘donor-acceptor molecules’ and absorb strongly in the visible region. Positioning effect on intramolecular charge transfer process on these isomeric compounds has been investigated. Comparative studies of the spectral, redox and structural properties of the reference isomeric compounds are discussed. Notably the colour of the para isomer (red) is distinctly different than that of the ortho isomer (blue). These compounds undergo chemically reversible reductions producing azo based free radicals. Electrochromic properties of the compounds are investigated.

Keywords: Positional isomers, Donor-acceptor molecules, Perchlorates, Triazinium cations, X-ray structures,
   Redox properties, Electrochromic properties

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1281-1289

 

An eight-connected metal organic framework based on Cu5 clusters: Synthesis, structure, magnetic and catalytic properties

Debajit Sarma & Srinivasan Natarajan*

Framework Solids Laboratory, Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012, India

Email: snatarajan@sscu.iisc.ernet.in

Received 12 May 2011; revised and accepted 12 July 2011

A reaction of copper acetate, 5-nitroisophthalic acid in a water-methanol mixture under solvothermal condition results in a new metal-organic framework compound, [Cu53-OH)2(H2O)6{(NO2)-C6H3-(COO)2}4].5H2O, (1). The compound contains Cu5 pentameric cluster units connected by 5-nitro isophthalate (NIPA) moieties forming a CdCl2-like layer, which are further connected by another NIPA moiety forming the three-dimensional structure. The water molecules in (1) can be reversibly adsorbed. The removal of water accompanies a change in the colour as well as a structural re-organization. Magnetic studies suggest strong antiferromagnetic correlations between the Cu5 cluster units. The compound (1) exhibits heterogeneous Lewis acid catalysis for the cyanosilylation of imines with more than 95 % selectivity. Compound (1) has been characterized by IR, UV-vis, TGA, powder XRD studies.

Keywords: Coordination polymers, Metal organic framework, Pentameric clusters, Cyanosilylation, Polycarboxylates, Imines, Copper

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1290-1297

 

Cyclometalated Ir(III) complexes containing ancillary pyrazole-based ligands

Tanima Hajra, Soumya Ghosh, Jitendra K Bera* & Vadapalli Chandrasekhar*

Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208 016, India

Email: vc@iitk.ac.in

Received 11 May, 2011; accepted 24 June 2011

A series of neutral mononuclear cyclometalated Ir(III) complexes, [Ir(ppy)2(Me2pzH)Cl] (1), [Ir(ppy)2(MepzH)Cl] (2), [Ir(ppy)2(Mepz)(MepzH)] (3), [Ir(ppy)2(Phpz)(PhpzH)] (4), [Ir(ppy)2(NPpz)(NPpzH)] (5) and [Ir(ppy)2(NP-2-pz)(NP-2-pzH)] (6) [where ppyH = 2-phenylpyridine; Me2pzH = 3,5-dimethylpyrazole; MepzH = 3-methylpyrazole; PhpzH =
3-phenylpyrazole;
NPpzH = 3-(1-naphthyl)pyrazole; NP-2-pzH = 3-(2-naphthyl)pyrazole) have been synthesised and structurally characterised. While (1) and (2) contain neutral pyrazole ligands which binds in a κ1 manner, in compounds (3)-(6), one of the pyrazole ligands is anionic while the other is neutral. In the latter also the pyrazole ligands bind to the metal in a κ1 manner. Further, the two types of pyrazoles interact with each other by H-bonded interaction. The photophysical and electrochemical properties of all of these compounds have been studied which reveal that the absorption/emission behaviour of these compounds is dependent on the Ir(ppy)2 unit of the complexes; the ancillary pyrazole ligands do not influence the photophysical behavior in any significant manner.

Keywords: Coordination chemistry, Cyclometallated complexes, Pyrazoles, Iridium, Photophysical properties,

Colour tuning, Luminescence

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1298-1302

 

A rhodamine-piperazine conjugate as a fluorogenic sensor for
mercury(II) ion in aqueous ethanol medium

Shubhra Bikash Maity & Parimal K Bharadwaj*

Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208 016, India

Email: pkb@iitk.ac.in

Received 6 May 2011; revised and accepted 1 July 2011

A bis-rhodamine piperazine conjugate has been synthesized in good yields as a pale yellow solid. The metal-free compound does not show any fluorescence upon excitation. However, specifically in presence of Hg2+ ion in aqueous ethanol, the color changes to pink and it exhibits high fluorescence upon excitation at 520 nm. Presence of other biologically relevant metal ions in the system does not affect the fluorescence output to any significant extent. Thus, this compound can be used as a chromogenic and fluorogenic sensor for Hg2+ ion in aqueous ethanol medium.

Keywords: Chemosensors, Fluorogenic sensors, Chemodosimetry, Spirolactum ring opening, Rhodamine, Piperazine

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1303-1307

 

Synthesis and characterization of some gold(I)-thiolate complexes having
N-methylimidazole moiety

Krishna P Bhabak & Govindasamy Mugesh*

Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore, 560 012, India

Email: mugesh@ipc.iisc.ernet.in

Received 28 May 2011; accepted 1 July 2011

Antithyroid drugs inhibit the thyroid hormone synthesis by inactivating the thyroid peroxidase and/or iodothyronine deiodinase, which are involved in iodination and deiodination reactions. Gold(I) compounds also inhibit the thyroid hormone synthesis by interacting with the selenocysteine residue of iodothyronine deiodinase. However, the chemical reactions between these two different classes of compounds have not been studied. In this paper, we describe the interaction of therapeutic gold(I) compounds with the commonly used thiourea-based antithyroid drug, methimazole. It is observed that the gold(I) phosphine complexes (R3PAuCl, where R = Me, Et, Ph) react with methimazole only upon deprotonation to produce the corresponding gold(I)-thiolate complexes. Addition of PPh3 to the gold(I)-thiolates produces (R3PAuPPh3)+ (R = Me or Et), indicating the possibility of ligand exchange reactions.

Keywords: Gold thiolate, Thiolates, Antithyroid drugs, Antiarthritic drugs, Methimazole, Ligand exchange,
Rheumatoid arthritis

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1308-1317

 

Ag@Pd core-shell nanoparticles

 

Deepa Jose & Balaji R Jagirdar*

Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012, India

Email: jagirdar@ipc.iisc.ernet.in

Received 13 May 2011; accepted 1 July 2011

Colloids of silver and palladium nanoparticles have been prepared by the Solvated Metal Atom Dispersion method. The as-prepared Ag colloid consisting of polydisperse nanoparticles is transformed into a monodisperse colloid by the digestive ripening process which involves refluxing the as-prepared colloid in the presence of a surfactant. In addition to the monodisperse nanoparticles, a small amount of an Ag-thiolate complex is also formed. Refluxing a mixture of the
as-prepared Ag and Pd colloids results in Ag@Pd core–shell nanoparticles. The core-shell structure has been established using a combination of techniques such as UV-visible spectroscopy, high resolution electron microscopy, energy filtered electron microscopy, energy dispersive X-ray analysis, high angle annular dark field imaging and powder X-ray diffraction.

Keywords: Nanoparticles, Bimetallic nanoparticles, Colloids, Solvated metal atom dispersion, Digestive ripening,
Core shell nanoparticles, Silver nanoparticles, Palladium nanoparticles, Silver colloid, Palladium colloid

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1318-1323

 

Synthesis and structural studies of copper(II) and nickel(II) complexes
containing 4,5-diazafluoren-9-one and pseudohalides:
Metal ion directed isomer preference

B Kishore Babu, S M Elahi, T Krishna Chary & M V Rajasekharan*

School of Chemistry, University of Hyderabad, Hyderabad 500 046, India

Email: mvrsc@uohyd.ernet.in

Received 26 May 2011; revised and accepted 12 July 2011

Three new hexacoordinated compounds, trans-[Cu(dafone)2(NCS)2] (1), trans-[Cu(dafone)2(NCO)2]·MeCN (2) and
cis-[Ni(dafone)2(NCS)2] (3) (dafone = 4,5-diazafluoren-9-one) have been prepared and X-ray crystallographically characterized. Structural study reveals that in these complexes each metal centre adopts a distorted octahedral geometry with an MN6 choromophore coordinated by four N atoms of chelated dafone ligands and two N atoms of terminal pseudohalides. The effect of dafone with a long chelate bite to adapt to the electronic preferences of the metal ions by varying the bite distance within certain limits is described. In the crystalline states, different kinds of non-covalent interactions promote dimensionalities in the studied complexes.

Keywords: Coordination chemistry, Copper(II), Nickel(II), Diazafluorenone, X-ray structure

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1324-1333

 

Ruthenium complexes of two different non-innocent ligands. Investigation of electronic structural aspects by experimental and DFT analysis

Tanaya Kundu, Abhishek Dutta Chowdhury, Biswajit Laha, Shaikh M Mobin &

Goutam Kumar Lahiri*

Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India

Email: lahiri@chem.iitb.ac.in

Received 22 April 2011; revised and accepted 21 June 2011

Synthesis and characterisation of the ruthenium complexes, [RuII(Q)(tppz)(Cl)]ClO4 (1) and [{RuII(Q)Cl}2-
(m-tppz)](ClO4)2 (2), incorporating redox noninnocent ligands, (Q = o-benzoquinonediimine, tppz = 2,3,5,6-tetrakis-
(2-pyridyl)pyrazine) are reported. The crystal structure of (1) and DFT optimized structure of (2) in comparison with the reported structures of analogous molecules establish that their valence configurations comprise the fully oxidized Qo and tppzo along with the Ru(II) center as well as non-planarity of the coordinated tppz. The reversible RuII/RuIII oxidation of (1) and two successive RuII/RuIII couples for (2) appear at 0.95 V and 0.96, 1.11 V vs SCE in CH3CN, respectively. The separation in potential of 0.15 V between the two successive oxidation processes in (2) leads to the comproportionation constant, Kc value of 3.5´102, which implies a rather weakly coupled (electrochemical) valence localized class II mixed valent RuIIRuIII state in (2)+. However, the DFT calculated Mulliken spin densities of (2)+ (Ru1, Ru2, Q, tppz and Cl of 0.333, 0.412, 0.070, -0.006 and 0.221, respectively) suggest an almost valence averaged situation. The compositions of molecular orbitals of (1) and (2) suggest appreciable (dp)RuII®p*(tppz)/p*(Q) back-bonding. Both the complexes exhibit multiple close-by reductions within the potential range of 0 to -2.0 V vs SCE in CH3CN which are assigned to be the ligand (Q/tppz) based reductions. The molecular orbital compositions predict Q based first reduction followed by tppz-based successive reductions in (1), whereas in (2) first reduction primarily takes place at the bridging tppz center followed by the reduction of Q. (1) and (2) exhibit multiple metal-to-ligand charge transfer transitions in the visible region due to the presence of two and three acceptor ligands, respectively. The key transitions in the visible region are assigned based on the TD-DFT calculations on optimized structures of (1) and (2).

Keywords:   Coordination chemistry, Electronic structures, Crystal structure, Non-innocent ligands, Redox properties,
DFT calculations, Ruthenium

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1334-1342

 

Synthesis and structural studies of cobalt(III) complexes of 5-methyl-

3-formylpyrazole-N(4)-ethyl/dimethyl thiosemicarbazone and nickel(II) complex of 2-S-methyl-6-methyl-4-formylpyrimidine-N(4)-ethyl thiosemicarbazone

 

Atanu Janaa, Saugata Konara, Sangita Raya, Shie-Ming Pengb, G H Leeb, Ray J Butcherc, Tian-Huey Lud,

Anil Kumar Barike, Sachindranath Palf & Susanta Kumar Kara, *

aDepartment of Chemistry, University College of Science, 92 APC Road, Kolkata 700 009, India

Email : skkar_cu@yahoo.co.in

bDepartment of Chemistry, National Taiwan University, Taipei, Taiwan, 106 ROC

cDepartment of Chemistry, Howard University, 2400 Sixth Street, NW, Washington, DC 200 59, USA

dDepartment of Physics, National Tsing Hua University, Hsinchu, Taiwan 300

eDepartment of Chemistry, St. Paul’s CM College, 33/1, Raja Rammohan Roy Sarani, Kolkata 700 009, India

fDepartment of Chemistry, Sree Chaitanya College, Habra, North 24 Parganas, West Bengal, India

Received 14 May 2011; revised and accepted 24 June 2011

Two cobalt(III) complexes [Co(L1)2]ClO4 (1) [HL1= N-ethyl-2-((5-methyl-1H-pyrazol-3-yl)methylidene)hydrazine-carbothioamide] and [Co(L2)2]ClO4.CH3OH.H2O (2) [HL2=N,N-dimethyl-2-((5-methyl-1H-pyrazol-3-yl)methylidene) hydrazinecarbothioamide] and one nickel(II) complex [Ni(HL3)2](ClO4)2.2H2O (3) [HL3=(2E)-N-ethyl-2-((6-methyl-2-(methylsulfanyl)pyrimidin-4-yl)methylidene)-hydrazinecarbothioamide] have been prepared and characterized by spectroscopic studies and X-ray diffraction measurements. Structural study reveals that the coordination environment around each metal center is distorted octahedral. The two tridentate (NNS) uninegative pyrazole derived ligands in the cobalt(III) complexes (1 and 2) and the two similar neutral pyrimidine derived ligands in the nickel(II) complex (3) are coordinated to the central metal ions in the meridional fashion. The pyrazole N and thiolato S in (1) and (2) and pyrimidine N and thione S in (3) are cis to each other while azomethine N atoms are trans coordinated.

Keywords: Coordination chemistry, Cobalt, Nickel, Pyrazoles, Pyrimidines, thiosemicarbazones, X-ray structure

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1343-1349

 

Recognition of nitrates in a discrete dimeric capsular assembly of a
triamide half-capsule

M Arunachalam & Pradyut Ghosh*

Department of Inorganic Chemistry, Indian Association for the Cultivation of Science,
2A & 2B Raja S. C. Mullick Road, Kolkata 700 023, India

Email: icpg@iacs.res.in

Received 4 May 2011; accepted 24 June 2011

A newly synthesized tripodal amide receptor for the recognition of planar anions such as nitrate and acetate is described. The tripodal host, L1, features a 1,3,5-substituted 2,4,6-trimethylbenzene scaffold bearing three convergent amide hydrogen bonding functionality and electron-withdrawing p-cyanobenzoyl terminals. The single-crystal X-ray crystallographic analysis on crystals obtained upon complexation of L1 with tetrabutylammonium nitrate in acetone shows the encapsulation of two NO3¯ ions inside the staggered dimeric capsular assembly of L1. On the other hand, complexation with tetrabutylammonium acetate in the same solvent system shows non-capsular recognition of acetate and a water molecule inside the receptor bowl. The p-cyano substitution in the aryl terminals assists the formation of dimeric capsular assembly of L1 by enhancing the hydrogen bonding tendency of the aryl C-H protons. Though L1 demonstrates capsule formation upon complexation with NO3¯, the geometrically similar AcO¯ shows non-capsular recognition in the solid state, which may be due the structural difference between the two anions.

Keywords: Coordination chemistry, Dimeric capsules, Anion recognition, Molecular recognition, Tripodal receptors, Nitrates, Acetates

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1350-1355

 

A fluoro-bridged dinuclear nickel(II) compound from tetrafluoroborate precursor: Making sense of a serendipitous reaction

Raj K Das, Tapas Ghatak, Ramesh C Samanta & Jitendra K Bera*

Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208 016, India

Email: jbera@iitk.ac.in

Received 9 May 2011; revised and accepted 21 June 2011

Reaction of [Ni(CH3CN)6][BF4]2 with [{(5,7-dimethyl-1,8-naphthyridin-2-yl)amino}carbonyl]ferrocene (L) in acetonitrile affords [NiII2(μ-F)2(L)4][BF4]2 (1). X-ray structure reveals a fluoro-bridged Ni2F2 core with each Ni additionally coordinated to four N atoms from the two chelating ligands. The molecular mass signal is observed at m/z (z = 2) 848 in the ESI-MS. It is believed that the bimetallic activation of BF4-, followed by the trifluoroborane exclusion aided by the ligand L, results in the formation of (1). The NH∙∙∙F interactions play an important role in the formation and stabilization of compound (1).

Keywords: Coordination chemistry, Dinuclear compounds, Fluoro-bridged compounds, Hydrogen bonds, Nickel, Ferrocene, Naphthyridine

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1356-1362

 

Incorporation of lead(II) by copper(II)-salicylaldimine type ligand complexes:
Cation–π interactions in controlling the distortion of
coordination geometry around lead(II)

 

Saptarshi Biswas & Ashutosh Ghosh*

Department of Chemistry, University College of Science, University of Calcutta, 92 APC Road, Kolkata 700 009, India

Email: ghosh_59@yahoo.com

Received 17 May 2011; accepted 24 June 2011

Two tri-nuclear, hetero-metallic copper(II)-lead(II) complexes, [(CuL1)2Pb(NCS)2] (1) and [(CuL2)2Pb(NCS)2] (2) have been synthesized by reacting the “ligand-complex” [CuL1] and [CuL2] respectively with Pb(CH3COO)2·3H2O and ammonium thiocyanate (where H2L1 = N,N¢-bis(salicylidene)-1,3-propanediamine and H2L2 = N,N¢-bis(α-methyl­-salicylidene)-1,3-propanediamine are the tetradentate di-Schiff base ligands) in EtOH-water medium. Both complexes have been characterized by X-ray single crystal structural analyses. In both structures, the central Pb(II) is six-coordinate, being bonded to four oxygen atoms from two terminal square planar CuL units and a couple of thiocyanate nitrogen atoms. The geometry around Pb(II) in both complexes is far from ideal octahedron and the distortion is more severe in (2). The coordination environment around all Cu(II) centres are square planar with different degrees of tetrahedral distortions. There are significant intra- and intermolecular cation-π interactions between the phenyl rings of the Schiff base and Cu(II) that seem to control the distortion around Pb(II).

Keywords: Coordination chemistry, Copper, Lead, Heterometallic complexes, Di-Schiff base ligands, Schiff bases,
Crystal structure, Cation–π interactions

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1363-1368

 

Synthesis and structural characterization of an open cage dithiatungstaborane [(CpW)2B4H4S2] cluster

Rajendra Singh Dhayal, Joseph Ponniah S, Satyanarayan Sahoo & Sundargopal Ghosh*

Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036, India

Email: sghosh@iitm.ac.in

Received 19 April 2011; revised and accepted 1 July 2011

Reaction of Cp#MCl4, (1 or 2) [(1): M = Mo, Cp# = Cp* (Cp* = η5-C5Me5) and (2): M = W, Cp# = Cp
(Cp = η5-C5H5)] with excess of [LiBH4.thf] followed by thermolysis with excess of [HS(CH2)nSH] (n = 2 or 3), leads to the formation of [(Cp*Mo)2B4H4S2] (3) or [(CpW)2B4H4S2] (4) respectively. Corresponding to (3) and (4), the compounds [(M)2B5H9] (M = CpW, (5) or Cp*Mo, (6)) are isolated as major product in both the cases. These new compounds have been characterized in solution by mass, 1H, 11B, 13C NMR spectroscopy. The structural types have been unequivocally established by X-ray crystallographic analysis of compounds (4).

Keywords: Coordination Chemistry, Metallaboranes, Open cage compounds, Chalcogens, Metallaheteroborane clusters, Tungsten, Boron

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1369-1379

 

Copper(II) complexes of 13-membered amide-based macrocyclic ligands:
Effect of electronic substituents on redox properties

Sushil Kumar & Rajeev Gupta*

Department of Chemistry, University of Delhi, Delhi 110 007

Email: rgupta@chemistry.du.ac.in

Received 12 May 2011; revised and accepted 24 June 2011

The present work discusses copper(II) complexes of 13–membered macrocyclic ligands carrying electronic substituents on the ligand periphery. The complexes have been thoroughly characterized including crystallographic investigations of two representative compounds. The crystal structures confirm that the metal center is coordinated by two deprotonated Namide and two neutral Namine atoms in an N4 basal plane within the macrocyclic cavity. The electrochemical studies suggest that the different electronic substituents present on the ligand periphery (–H, –Cl, –CH3, and –OCH3) significantly alter the CuIII–CuII potential values. Based on the electrochemical findings, the transient Cu(III) species generated coulometrically are characterized by their absorption spectra.

Keywords: Coordination chemistry, Copper, Macrocyclic ligands, Crystal structures, Electrochemistry,
Electronic effects

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1380-1387

 

Heterogeneous Stille and Sonogashira cross-coupling reactions over
palladium anchored mesoporous silica catalyst

Susmita Bhunia & Subratanath Koner*

Department of Chemistry, Jadavpur University, Kolkata 700 032, India

Email: snkoner@chemistry.jdvu.ac.in

Received 3 May 2011; revised and accepted 25 July 2011

A Pd-based heterogeneous catalyst (Pd(II)-MCM-41) derived from post-synthesis modification of mesoporous silica,
MCM-41, has been successfully employed in catalytic Stille and Sonogashira cross-coupling reactions. The catalyst affords good yields in all cross-coupling reactions. Notably, the catalyst is capable of activating less reactive chlorobenzene with moderate yield in both the coupling reactions. The reactions take place smoothly in air without any activating ligand. It is observed that in the case of Stille reactions, the less expensive organotin reagent, Ph3SnCl, can be used instead of the conventional expensive reagent, Bu3SnPh. Both the organotin reagents exhibit comparable reactivity in Stille reactions catalyzed by Pd(II)-MCM-41. The catalyst is easily recoverable and reusable at least three times without significant loss of catalytic activity.

Keywords: Catalysts, Heterogeneous catalysts, Cross coupling reactions, Stille reaction, Sonogashira reaction,
Mesoporous catalysts, Palladium, Silica

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1388-1393

 

Aminosilicate sol-gel embedded core-shell (TiO2-Au)nps nanomaterials modified electrode for the electrochemical detection of nitric oxide

Alagarsamy Pandikumar & Ramasamy Ramaraj*

Centre for Photoelectrochemistry, School of Chemistry, Madurai Kamaraj University,
Madurai 625 021, India
Email: ramarajr@yahoo.com

Received 1 June 2011; revised and accepted 14 June 2011

A glassy carbon electrode modified with amine functionalized silicate sol-gel supported core-shell titanium dioxide–gold nanocomposite materials (EDAS/(TiO2-Au)nps) has been prepared and used as an electrochemical sensor for nitric oxide detection. The aminosilicate supported core-shell nanomaterials have been synthesized by the chemical reduction of HAuCl4 and deposition of the formed Aunps on TiO2 nanoparticles in the presence of N-[3-(trimethoxysilyl)propyl]-ethylene diamine as a support matrix and as a reducing agent. The so-prepared EDAS/(TiO2-Au)nps nanomaterials and the corresponding films have been characterized by spectral and electrochemical methods. A set of experimental conditions has been optimized for the fabrication of sensor electrode. The electrochemical properties of the GC/EDAS(TiO2-Au)nps modified electrode and the electrochemical detection of NO have been  studied. The Osteryoung square wave voltammetric measurements reveals that the current response observed at the GC/EDAS(TiO2-Au)nps modified electrode for different concentrations of NO is linear with the  lowest detection limit of 1 μM.

Keywords: Electrocatalysis, Sol-gel process, Modified electrodes, Sensors, Aminosilicate, Nitric oxide, Titania, Gold

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1394-1402

 

Synthesis and reactivity of cobalt complexes derived from
tris(2-pyridylthio)methane ligand: Structural characterization of
cobalt(III) complexes containing cobalt–carbon bond

Partha Halder & Tapan Kanti Paine*

Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, 2A & 2B Raja S C Mullick Road
Jadavpur, Kolkata 700 032, India

Email: ictkp@iacs.res.in

Received 17 May 2011; revised and accepted 25 July 2011

The synthesis, characterization and reactivity of a cobalt(II) complex, [(HL1)CoII(PyS)](ClO4) (1) (where
HL1 = tris(2-pyridylthio)methane and PyS = monoanionic pyridine-2-thiolate) are discussed. Complex (1) reacts with molecular oxygen to yield a mononuclear low-spin cobalt(III) complex, [(L1)CoIII(PyS)](ClO4) (2). On the other hand, treatment of (1) with a protic acid (pyridinium perchlorate) followed by a base (triethylamine) and dioxygen
forms an isomeric cobalt(III) complex, [(L2)CoIII(PyS)](ClO4) (3) (L2 = 1-[bis(2-pyridylthio)methyl]pyridine-2-thione). Ligand HL1 (in 1) rearranges to L2 (in 3) during the reaction as a result of C–S bond cleavage and subsequent C–N bond formation. X-ray crystal structures of both (2) and (3) reveal a distorted octahedral coordination geometry at cobalt(III) center with a strong cobalt–carbon bonding interaction. A four-coordinate distorted tetrahedral cobalt(II) complex, [CoII(PySH)4](ClO4)2 (4) is formed via C–S bond cleavage of HL1 in the reaction of (1) with an excess amount of pyridinium perchlorate. The electronic structure of (2) as established by DFT calculation suggests a delocalized LUMO with significant contribution from the metal ion. The organocobalt(III) complex converts to an air-stable organocobalt(II) complex (2red) upon one-electron reduction.

Keywords: Organometallic compounds, Organocobalt complexes, Metal–carbon bond, Solid state structure, Cobalt,    Oxidation

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1403-1409

 

Synthesis, structure and electrochemical properties of some thiosemicarbazone complexes of ruthenium

Sayanti Dattaa, Michael G B Drewb & Samaresh Bhattacharyaa, *

aDepartment of Chemistry, Inorganic Chemistry Section, Jadavpur University, Kolkata 700 032, India

Email: samaresh_b@hotmail.com

bDepartment of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD, UK

Received 13 May 2011; revised and accepted 24 June 2011

Reaction of salicylaldehyde thiosemicarbazone (L1), 2-hydroxyacetophenone thiosemicarbazone (L2)
and 2-hydroxynapthaldehyde thiosemicarbazone (L3) with [Ru(dmso)4Cl2] affords a family of three dimeric complexes
(1), (2) and (3) respectively. Crystal structure of the complex (3) has been determined. In these complexes, each monomeric unit consists of one ruthenium center and two thiosemicarbazone ligands, one of which is coordinated to ruthenium as O,N,S-donor and the other as N,S-donor forming a five-membered chelate ring. Two such monomeric units remain bridged by the sulfur atoms of the O,N,S-coordinated thiosemicarbazones. Due to this sulfur bridging, the two ruthenium centers become so close to each other, that a ruthenium-ruthenium single bond is also formed. All the complexes are diamagnetic in the solid state and in dimethylsulfoxide solution show intense absorptions in the visible and ultraviolet region. Origin of these spectral transitions has been established from DFT calculations. Cyclic voltammetry on the complexes shows two irreversible ligand oxidations on the positive side of SCE and two irreversible ligand reductions on the negative side.

Keywords: Coordination chemistry, Coordination modes, Thiosemicarbazones, Ruthenium

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1410-1417

 

Synthesis and structural characterization of potassium coordination
polymers based on a copper-bis(dithiolato) complex:
Role of coordinating solvents and counter cation

Ramababu Bolligarlaa, Bharat Kumar Tripuramallua, Vudagandla Sreenivasulub & Samar K Dasa, *

aSchool of Chemistry, University of Hyderabad, Hyderabad 500 046, India

Email: skdsc@uohyd.ernet.in/ samar439@gmail.com

bBioPolymer and Thermophysical Lab, Department of Chemistry, Sri Venkateswara University,
Tirupati 517 502, India

Received 11 May 2011; revised and accepted 14 June 2011

We have synthesized two new potassium metal coordination polymers {[K(CH3COCH3)3][Cu(btdt)2]}n (1) and {[K(CH3CN)2][Cu(btdt)2]}n (2) of diverse dimensionality based on a copper coordination complex [CuIII(btdt)2]1−
({btdt}2– = 2,1,3-benzenethiadiazole-5,6-dithiolate). Recrystallization of the dark brown solid, obtained from the reaction mixture of H2btdt, KOH and CuCl2·2H2O in MeOH, from the coordinating solvents acetone and acetonitrile results in the formation of 3-D and 2-D extended networks in compounds (1) and (2) respectively. The crystal structures of (1) and (2) have been discussed in comparison with those of recently reported sodium coordination polymers {[Na(CH3OH)4][Au(btdt)2]}n (3), [Na(DMF)2][Au(btdt)2]}n (4) and {[Na(CH3CN)2][Au(btdt)2]}n (5). Compounds (1) and (2) have additionally been characterized by routine spectroscopy including elemental analyses.

Keywords: Coordination Chemistry, Coordination polymers, Metal-organic frameworks, Crystal structures, Counter cation,
Coordinating solvents, Potassium, Copper

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1418-1428

 

Osmium(II) mixed-chelate derived from imidazole 4,5-bis(benzimidazole)
and 2,2¢-bipyridine as multichannel sensor for anions: Synthesis, structural characterization and binding studies

Debasish Saha, Shyamal Das, Dinesh Maity & Sujoy Baitalik*

Department of Chemistry, Inorganic Chemistry Section, Jadavpur University, Kolkata 700 032, India

Email: sbaitalik@hotmail.com

Received 6 April 2011; accepted 12 July 2011

Mixed-ligand complex of composition [(bpy)2Os(H3Imbzim)](ClO4)2∙2H2O (1), where H3Imbzim = 4,5-bis(benzimidazole-2-yl)imidazole and bpy = 2,2¢-bipyridine, has been synthesized and characterized using standard analytical and spectroscopic techniques. The X-ray crystal structure of the complex has been determined which showed that it crystallized in triclinic form with the space group P-1. The anion binding properties of the complex has been thoroughly investigated in solution using absorption, emission, and 1H NMR spectral measurements. The metalloreceptor acts as sensor for F-, AcO-, and to some extent for H2PO4- anions. Although at relatively lower concentration of anions the 1:1 H-bonded adduct is formed, in the presence of excess of anions deprotonation of the imidazole N–H fragments occurs which is accompanied by a distinct change of color. Double deprotonation is also observed in the presence of hydroxide. The binding affinities of different anions towards the receptors have been evaluated. Cyclic voltammetry measurements carried out in acetonitrile have provided evidence in favor of an anion-dependent electrochemical response of the receptor with F- and AcO- ions.

Keywords: Coordination chemistry, Metalloreceptors, Multichannel sensors, Sensors, Anion sensors, Fluoride, Acetate, Anion binding

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1429-1435

 

Syntheses, structures and molecular properties of two mononuclear cobalt(III) halide complexes containing a tetradentate N-donor Schiff base

Sumitava Khana, Kishalay Bhara, Subhasis Roya, Krishnakumar Ramachandranb
& Barindra Kumar Ghosha, *

aDepartment of Chemistry, The University of Burdwan, Burdwan 713 104, India

bChemistry and Physics of Materials Unit, Jawaharlal Neheru Center for Advanced
Scientific Research, Jakkur, Bangalore 560 064, India

Email: barin_1@yahoo.co.uk

Received 21 April 2011; accepted 21 June 2011

Two mononuclear cobalt(III) compounds of the general formula trans-[Co(L)X2]ClO4 [L = N,N¢-(bis(pyridine-2-yl)- benzylidine)-1,2-ethanediamine; (1), X = Cl; (2), X = Br] have been synthesized using a one-pot reaction of a 1:1:1 molar ratio of CoX2.6H2O, (L) and NaClO4 in MeOH solutions at room temperature. The complexes are characterized by physicochemical and spectroscopic methods. Structural analyses of (1) and (2) reveal that the cobalt(III) center adopts a distorted octahedral geometry with CoN4Cl2 and CoN4Br2 chromophores, respectively. Four N atoms of (L) define the equatorial plane and two terminal halides are in axial positions. In the crystalline states, C-H…Cl/C-H…Br hydrogen bonds along with C-H…π interactions promote dimensionality in (1) and (2). In MeCN solutions, both the diamagnetic compounds show a nearly-reversible one-electron reductive response corresponding to cobalt(III)-cobalt(II) couple. They show luminescence in MeOH solutions.

Keywords: Coordination chemistry, Cobalt, Schiff bases, X-ray structure, Redox behavior, Luminescence

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1436-1442

 

Models for photosynthetic reaction center: Synthesis, structure and electrochemical properties of a cofacial di-palladium bisporphyrin

Arvind Chaudhary, Ranjan Patra & Sankar Prasad Rath*

Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208 016, India

Email: sprath@iitk.ac.in

Received 9 May 2011; accepted 1 July 2011

A novel cofacial dipalladium(II) bisporphyrin (Pd2DEP) of Pacman-type is reported herein. Structural characterization suggests very strong π-π interactions between two planar porphyrins that closely mimic the spatial orientation observed in the so called ‘special pair’. The electrochemical response reveals four consecutive ring-centered oxidations in CH2Cl2, indicative of strong through-space electronic communication between two redox-active Pd-porphyrins. At 0.66V, one Pd-porphyrin unit is oxidized to generate a radical cation at a potential much lower than that of monomeric unit (PdOEP), owing to the increased electron density in the bisporphyrin scaffold. However, due to the presence of strong inter-macrocyclic interactions, the second Pd-porphyrin is then oxidized at a significantly higher potential (0.97 V) to produce radical cation species. In the bis(radical cation) state, electrostatic repulsion induces change in the geometry due to flexible spacer which eventually forces an increase in the porphyrin-porphyrin distance. As a result, the second oxidation of both the porphyrin radical cations is observed at 1.42 V as a single reversible two-electron process. The overall oxidation process thus demonstrates strong electrostatic communication between the two macrocycles in Pd2DEP and also provides a means of switching, in a clapping motion, from a closed to an open Pacman structure under electrochemical stimulus.

Keywords: Porphyrins, Palladium, Porphyrin dimers, Pi-pi interactions, Molecular motions, Electrochemical properties

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1443-1449

 

Trans-dichlorobis(N-p-tolylpyridin-2-amine)palladium(II): Synthesis, structure, fluorescence features and DNA binding

Suman Kundu, Suvendu Maity, Ranjan Bhadra & Prasanta Ghosh*

Department of Chemistry, R K Mission Residential College, Narendrapur, Kolkata 700 103, India

Email: ghoshp_chem@yahoo.co.in

Received 16 May 2011; revised and accepted 25 July 2011

Reaction of N-p-tolylpyridin-2-amine (LMe) with H2PdCl4 in boiling acetonitrile and ethanol solvents mixture
(1:1) affords trans-Pd(LMe)2Cl2 (1) in high yield. (1) is substantiated by spectral data, single crystal X-ray structure determination, etc. Both (LMe) and (1) absorb strongly in the UV region (λmax, nm (ε, 104 M–1cm–1), DCM: (LMe),
310 (1.97), 276 (4.95); (1), 320 (4.36), 270 (6.98). (LMe) is brightly fluorescent due to intra-ligand charge transfer singlet excited state (λex = 332 nm, λem = 400 nm; Φ = 0.621 measured with respect to anthracene) as elucidated by DFT and TD DFT calculations. In (1), the luminescence of (LMe) is significantly (~ 97 %) quenched (Φ = 0.016) and the fluorescence parameters are red shifted (λex = 378 nm, λem = 430 nm). Binding of (1) to CT-DNA has been investigated by UV-vis spectrum confirming a significant interaction with the intrinsic binding constant as Kb = ~ 9.78 × 105 M-1 and CT-DNA-ethidium bromide fluorescence quenching experiment giving the apparent binding constant as Kapp = 9.02 × 105 M –1.

Keywords: Density functional calculations, Fluorescence quenching, Palladium, DNA binding

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1450-1456

 

Ferromagnetic vs antiferromagnetic coupling in structurally analogous binuclear complexes based on salen type ligand

Rampal Pandeya, Joan Ribasb, Montserrat Corbellab & Daya Shankar Pandeya, *

aDepartment of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi 221 005, UP, India

Email: dspbhu@bhu.ac.in

bDepartamento de Química Inorgánica, Universitat de Barcelona, Martí i Franqués, 1-11, 08028, Barcelona, Spain

Received 14 May 2011; revised and accepted 22 July 2011

Syntheses of the dinuclear complexes [Co(C23H18N2O2)]2 (1), [Cu(C23H18N2O2)]2.H2O (2), [Ni(C23H18N2O2)]2 (3), [Zn(C23H18N2O2)]2 (4) and [Cd(C23H18N2O2)]2 (5) containing the Schiff base ligand N,N′-bis(2-hydroxybenzilidene)-2,4,6-trimethylbenzene-1,3-diamine have been described. The complexes under investigation have been characterized
by elemental analyses, IR, NMR (1H, 13C), electronic absorption, emission and EPR spectral studies. The structure of
(1) has been determined by X-ray single crystal analyses. Variable temperature magnetic susceptibility measurements on
(1) and (2) reveal that the former displays antiferromagnetic coupling (J = -0.21 ± 0.1 cm-1), while the latter exhibits ferromagnetic coupling (J = + 1.23 ± 0.1 cm-1).

Keywords: Coordination chemistry, Supramolecular assembly, Polymetallic complexes, Dinuclear complexes, Schiff bases, Ferromagnetic coupling, Antiferromagnetic coupling, Electrochemical properties, Cryomagnetic properties, Cobalt, Copper, Nickel, Zinc, Cadmium

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1457-1462

 

Density functional theory calculations on biological S-transfer: Insight into the mechanism of rhodanese

Subal Dey & Abhishek Dey*

Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India

Email: icad@iacs.res.in

Received 8 June 2011; revised and accepted 10 August 2011

Biological sulfur transfer (S-transfer) is a key step in the synthesis of metabolites, CN- detoxification and assembly of iron-sulfur clusters. Computational results addressing the thermodynamics of the S-transfer reactions from thiosulfate (natural S-donor) to HCN and thiol are presented. These calculations indicate that S-transfer from thiosulfate to HCN and thiol is possible only in the anionic forms of these species. However these species have pKa values significantly higher than physiological pH value (i.e., they are protonated in physiological pH and incapable of S-transfer). In the rhodanese active site, basic residues are present to deprotonate the catalytic cysteine group which accepts the S-atom from thiosulfate. The resultant perthiol species transfer S-atom to CN- in a synchronous S-atom and H+ transfer step facilitated by the two arginine residues present in the rhodanese active site.  Based on these calculations, a mechanism is proposed for the rhodanese catalyzed CN- detoxification pathway.

Keywords: Density functional calculations, S-transfer reactions, Cyanide detoxification, Rhodanese

 

Indian Journal of Chemistry

Vol. 50A, Sept-Oct 2011, pp. 1463-1468

 

Zinc and cadmium complexes of a Schiff base ligand derived from diaminomaleonitrile and salicylaldehyde: Syntheses, characterization, photoluminescence properties and DFT study

Averi Guhaa, Jaydeep Adhikarya, Tapan Kumar Mondalb & Debasis Dasa, *

aDepartment of Chemistry, University of Calcutta , 92, APC Road, Kolkata 700 009, India

bDepartment of Chemistry, Jadavpur University , Kolkata 700 032, India

Email: dasdebasis2001@yahoo.com

Received 11 May 2011; revised and accepted 1 July 2011

Zn(II) and Cd(II) complexes of a 1+1 condensed Schiff base derived from salicylaldehyde and diaminomaleonitrile has been synthesized and characterized. Electronic and photoluminescence spectral properties of the complexes as well as the free ligand have been investigated and a thorough DFT study has been performed to rationalize the spectral behavior.

Keywords: Coordination chemistry, Zinc, Cadmium, Schiff bases, Diaminomaleonitrile, Fluorescence properties