• A Shunmugasundaram

      Articles written in Journal of Chemical Sciences

    • 13C NMR substituent induced chemical shifts in the side-chain carbons of α,β-unsaturated sulphones

      C Srinivasan P K Ganesan A Shunmugasundaram N Arumugam

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      The13C NMR chemical shifts of α,β-unsaturated sulphones of the types E-2-aryl-1-phenyl-sulphonylethylenes (series I) and E-1-arylsulphonyl-2-phenylethylenes (series II) have been measured in CDCl3 solution. The chemical shifts of the side-chain and a few ring carbons have been correlated with various single and multiparameter linear free energy relationships. Analysis of the13C NMR spectral data by a dual substituent parameter equation shows that the resonance effect is the dominant factor at C-α in series I and C-β in series II. The inductive effect is predominant at C-β in series I with a reverse substituent effect at this carbon atom. The reverse inductive contribution is explained in terms of π-polarisation mechanism.

    • 12-B heteropolyanions as ligands: Synthesis, spectral characterisation and solution studies of [MnIVThMo12O42]4−, [MnIVUMo12O42]4− and [VIVCeMo12O42]4−

      R Murugesan T Jeyabalan P Sami A Shunmugasundaram

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      Interaction of 12-B heteropolyanions, [XMo12O42]8−, whereX=Ce, Th and U, with tetravalent transition metal ions MnIV and VIV results in the formation of three well defined complexes, viz., (NH4)4[MnIVThMo12O42]·10H2O (I), (NH4)4[MnIVUMo12O42]·8H2O (II) and (NH4)4[VIVCeMo12O42]·8H2O (III), which are characterised by IR, Raman and EPR spectroscopies. Negative shift in the stretching frequency of Mo-Ot bond in IR spectra and appearance of a strong band at 818 cm−1 in Raman spectra support the formation of these complexes. EPR spectra of complexes (I) and (II) show a predominant signal atg=4 and a weak signal atg=2 (with hyperfine coupling from55Mn), characteristic of d3 system, (S=3/2 andI=5/2) with large zero field splitting, showing distortion from octahedral symmetry. EPR parameters of the vanadium complex (III) show thed-electron to be more localised on vanadium(IV) supporting the formulation of vanadium not to be a part of the “Mo12” unit. The oxidising property of complexes (I) and (II) is studied using glucose as the substrate.

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