• Chintamani Mande

      Articles written in Proceedings – Section A

    • X-ray spectroscopic study of the thiomalic acid complex of cobalt

      Chintamani Mande A R Chetal

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      The cobalt K absorption spectrum has been studied in thiomalic acid complex of cobalt using a bent crystal X-ray spectrograph. It has been observed that the position of the absorption discontinuity taken with the freshly prepared complex differs from that of the discontinuity obtained with the complex kept in air for about 24 hours. It has been shown that this shift of the absorption edge is due to the change in valency of cobalt in the complex. The shape of the absorption discontinuity has revealed that the complex has an octahedral structure with the hybridizationsp3d2. On the molecular orbital theory the electronic configuration in this complex can be described asa1gEmphasis>2t1uEmphasis>6egEmphasis>4t2gEmphasis>4egEmphasis>*2.

    • X-Ray spectroscopic evidence for chemical bonding in manganese selenide (MnSe)

      Chintamani Mande A S Nigavekar

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      K absorption spectra of manganese and selenium have been recorded photographically in the pure metals and in the intermetallic compound manganese selenide (MnSe), employing a bent crystal X-ray spectrograph. It has been observed that the Mn K absorption discontinuity in MnSe shifts by 5·6 eV toward the high energy side with respect to the discontinuity in the pure metal. On the other hand, the Se K edge in MnSe is found to shift by 3·4 eV toward the low energy side with respect to the discontinuity in pure selenium. Also, emission work has revealed that the Mn Kβ5 band in the compound shifts by about 5 eV toward the high energy side with respect to that in the pure metal. It has been shown that these results confirm the resonatingp3 type of chemical bonding in the compound, as suggested theoretically by Pearson.

    • X-ray spectroscopic study of chemical bonding in MnSe2 and CoSe2

      Chintamani Mande A S Nigavekar

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      X-ray absorption study of two intermetallic compounds MnSe2 and CoSe2 has been carried out using a Cauchois type bent crystal spectrograph. The metal K absorption edges in both the compounds are found to shift toward the high energy side with respect to the discontinuities in the pure metals. On the other hand, the Se K absorption edge in both these compounds is found to shift toward the lower energies. Emission study of the compound MnSe2 has shown that the Mn Kβ5 band in this compound is shifted toward the high energy side with respect to that in the pure metal. From the magnetic data and the results obtained in this work it is possible to obtain the chemical bonding pictures in these compounds. For MnSe2 the bondings sp3d2 for the metal atom andsp3 for the metalloid atom have been suggested. For CoSe2 the bondings appear to bed2sp3 for the metal atom andsp3 for the metalloid atom. These bondings are compatible with the pyrite type structure of these compounds. It is possible to explain the electrical behaviour of the compounds on the basis of these bonding pictures.

    • X-ray spectroscopic study of chemical bonding in NiSe and NiSe2

      Chintamani Mande A S Nigavekar

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      The K absorption spectra of nickel and selenium have been recorded photographically in the pure metals and the compounds NiSe and NiSe2. It has been observed that the Ni discontinuity shifts toward the high energy side with respect to that in the pure metal by about 5.0 eV for NiSe and about 6.7 eV for NiSe2. The Se edge in both these compounds is found to shift by about 2.6 eV toward the low energy side with respect to that in pure selenium. From these results it is possible to obtain the bonding pictures for the compounds. The compound NiSe appears to have resonating p3 type of bonding. For NiSe2 the orbitals involved in the bonding are d2sp3 for the metal atom and sp3 for the metalloid atom. The electrical behaviour of the compounds has been explained on the basis of these bonding pictures.

    • The shapes of the LIII X-ray absorption discontinuity of rhenium in compounds

      Chintamani Mande A V Pendharkar M C Chakravorti

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      The X-ray LIII absorption edge of rhenium in the pure metal and in two compounds, namely, K2ReCl6 and KReO4 has been studied using a Cauchois type bent crystal spectrograph of 40 cm diameter. The splitting of the main absorption discontinuity has been observed for the first time in the compounds. This splitting and the edge structure of the Re LIII discontinuity in the compounds have been interpreted on the basis of molecular orbital diagrams. The crystal field splitting, Δ, has been determined experimentally in both the compounds in the solid state.

    • An NMR study of the thiomalic acid complex of cobalt

      S G Modak P L Khare Chintamani Mande

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      An NMR study of the thiomalic acid complex of cobalt has been carried out at pH 2.6. The results show that the freshly prepared complex is paramagnetic and it gradually changes to the diamagnetic state, the reaction being complete in about 24 hours. It has been shown that the fresh complex has the hybridization sp3d2, whereas the stable complex has the hybridization d2sp3. The results have been confirmed by measuring the change in the magnetic susceptibility of the complex with time.

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