• G S S Saini

      Articles written in Journal of Chemical Sciences

    • Resonance Raman studies of metalloporphyrins

      A L Verma G S S Saini N K Chaudhury

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      The biological and chemical importance of metalloporphyrins has stimulated extensive studies on the physicochemical properties of the macrocycle during recent years. Because of their strong absorption in the visible and near-UV region and the availability of tunable lasers, resonance Raman scattering from metalloporphyrins has emerged as a very sensitive and selective technique for probing structural details and nature of bonding at physiologically relevant concentrations. The variations of intensities and depolarization ratios as functions of excitation wavelength, band position and band shapes under different conditions have provided detailed information about the excited electronic states, structure, spin, oxidation and coordination states of the central metal and electron transfer processes in these systems. We shall illustrate the potential of this technique based on some selected examples including photo-reduction and photo-oxidation processes in metalloporphyrins.

    • Fourier-transform infrared spectroscopic studies of dithia tetraphenylporphine

      Sandeep Mishra Sarvpreet Kaur S K Tripathi C G Mahajan G S S Saini

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      We present here infrared absorption spectra of dithia tetraphenylporphine and its cation in the 450–1600 and 2900–3400 cm−1 regions. Most of the allowed IR bands are observed in pairs due to overallD2h point group symmetry of the molecule. The observed bands have been assigned to the porphyrin skeleton and phenyl ring modes. Some weak bands, which are forbidden underD2h, also appear in the spectra due to the distortion of the molecule from planarity-caused by the out-of-plane positioned N and S atoms. Increased intensity of some phenyl ring bands compared to free-base tetraphenylporphine is explained on the basis of rotation of phenyl rings towards the mean molecular plane. Contrary to the point group symmetry of cation of dithia tetraphenylporphine, certain bands are observed to be degenerate due to identical bonding arrangements in pyrrole rings of the cation

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