• Uday Mukhopadhyay

      Articles written in Journal of Chemical Sciences

    • Synthesis and characterisation of phenoxo bridged dinuclear complexes of copper(II)

      Sami Mukhopadhyay Uday Mukhopadhyay Debashis Ray

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      A series of model complexes for the type III site, in oxidised hemocyanin, containing Cu2(μ-0Ph)3+ core have been synthesised using a heptadentate ligand (H3L) formed from the Schiff base condensation of triethylenetetramine and salicylaldehyde. The ligand provides one imine and one inbuilt imidazole nitrogen and two phenolic oxygen donors with both five- and six-membered chelate rings to each metal centre. In the pentacoordinated complexes [Cu2(L)X]·nH2O, a third exogenous bridging ligand is present. The TG curve indicates the loss of lattice water molecules between 70 and 125°C. The residue after decomposition is CuO above 550°C. Theg values of theX-band EPR spectrum of [Cu2L(μ-OAc)]·2H2O in methanol glass (77 K) are typical of a variety of bridged copper(II) dimers. The copper-copper magnetic interaction is dependent on the presence and nature of X in these complexes.

    • Dicopper(II) complexes with sulphur bridge: Syntheses, spectral and electrochemical properties

      Uday Mukhopadhyay Debashis Ray

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      A family of dithiocarbonate sulphur bridged dinuclear copper(II) complexes containing [Cu2II(μ-Rx)μ-OPh)]2+ (R=Me, Et,nPr,iPr,nBu, Bz; x=OCS2) core with supporting weak imidazolidine bridge has been synthesized for the first time using aμ-bis(tetradentate) amine phenol ligand (H3L). The ligand reacts with CuCl2·2H2O and different KRx in aqueous acetone in air affording crystalline [Cu2(μ-Rx)(μ-L)]·2H2O in excellent yields. Both the Cu(II)-Cu(II) and Cu(II)-Zn(II) complexes have MN2O2 S coordination spheres. Taking the help of one exogenous bridging ligand (Rx) the triply bridged CuII-CuII intimate complex is formed in a Schiff-base ligating environment. The ligand provides one imine and one inbuilt imidazolidine nitrogen and two phenolic bridging and terminal oxygen donors forming five- and six- membered chelate rings around each metal centre. In the pentacoordinated complexes [Cu2(μ-Rx)(μ-L)]·2H2O, dithiocarbonate ligands are present as exogenous bridging ligands. The presence of large polarizable sulphur atoms around each copper(II) centre significantly modify the nature of the complexes to be electroactive as detected by cyclic voltammetry, compared to the analogous exogenous acetate bridging complexes. The copper-copper magnetic interaction is dependent on the nature of different R groups and presence of S donors. Both electron transfer behaviours and magnetic properties of copper(II)-copper(II) complexes are assessed with respect to a heterodinuclear copper(II)-zinc(II) complex in identical ligating environment.

    • Imidazolidine ring as a reduced heterocyclic spacer in a new all-N-donor μ-bis (bidentate) Schiff base ligand: Synthesis, characterization and electron transfer properties of imidazolidine-bridged dicopper complexes

      Manindranath Bera Prasant Kumar Nanda Uday Mukhopadhyay Debashis Ray

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      Low-temperature stoichiometric Schiff base reaction in air in 3:1 mole ratio between benzaldehyde and triethylenetetramine (trien) in methanol yields a novel tetraaza μ-bis (bidentate) acyclic ligand L. It was characterized by elemental analysis, IR, EI mass and NMR (1H and13C) spectra. The formation of a five-membered imidazolidine ring from the ethylenediamine backbone as a spacer-cumbridging unit gives rise to a new type of imidazolidine-bridged ligand. A geometric optimisation was made of the synthesized ligand and its complexes by the method of molecular mechanics (MM2) method in order to establish the stable conformations. This hitherto unknown tetraaza acyclic ligand affords new cationic dicopper(I/I) and dicopper(II/II) complexes in good yield. Dicopper(II/II) complex displays weakd-d transition bands in the visible region, while dicopper(I/I) complex displays strong MLCT band in the same region. Both the dinuclear complexes are of non-intimate nature and show interesting solution electrochemical behaviour. EPR spectral study of μ-bis (imidazolidino) bridged dicopper(II/II) complex also supports the non-communicative nature of the two copper centres within the same molecule

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