Articles written in Journal of Chemical Sciences

    • Formation and Structure of Iodine: Water (H2O-I2) charge-transfer complex


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      Absorption spectra of iodine molecule in water confirm the formation of H2O-I2 C-T complex with a shifted iodine visible band at 461 nm and a charge transfer (C-T) band at 202 nm. Iodine oxidizes water leading to the formation of I-3 ion. Absorption bands of I-3 the ion at 351 nm and 284 nm are observed in Iodine solution in water. The concentration of I-3 is about 1% of H2O-I2 C-T complex when iodine is dissolved in water with e value of 16771M-1cm-1 at 351 nm. DFT calculation shows that two I2 molecules can bind to two lone pairs of O in H2O nearly in tetrahedral geometry with stabilization energy - 8.3 kcal/M.But, one I2 bonded to one of the lone pairs on oxygen and one H2O molecule is hydrogen-bonded to the second lone pair on oxygen in nearly tetrahedral geometry is more stable with energy -8.5 kcal/M. By plotting experimental ionization energies of H2O and I2 from photoelectron spectroscopy, MOs of H2O-I2 C-T complex is constructed. C-T band at 202 nm (6.14 eV) is the excitation from the stabilized sp3 hybridized oxygen lone pair in H2O to destabilized σ* orbital of I2 in the H2O-I2 C-T complex.

    • An efficient Ti0.95Cu0.05O1.95 catalyst for ipso – hydroxylation of arylboronic acid and reduction of 4-nitrophenol


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      A stable, active and selective Ti0.95Cu0.05O1.95 catalyst, crystallized in anatase TiO2 structurewith 5% Cu2+ ions substituted for Ti4+ ions with 5% oxide ion vacancy has been synthesized by solutioncombustion method. The catalyst was coated over a cordierite monolith (Mg2Al4Si5O18) by solution combustionmethod. By the first principle density functional theory (DFT) calculations, 48 atoms bulk structurehas been optimized and density of states (DOS) has been calculated. Ti – O bond distribution in Ti0.95Cu0.05O1.95 has been compared with pure TiO2. Bond distribution analysis has shown longer Cu – O and Ti –O bonds compared to those in CuO and TiO2 creating Cu2+ and oxide ion vacancy as electrophilic andnucleophilic active sites, respectively. This catalyst was found to be very active for ipso – hydroxylation ofarylboronic acid and 4-nitrophenol reduction reactions at room temperature. Catalyst coated cordieritemonolith was used in the recycling process of the reaction for 20 cycles and cumulative turnover frequencywas found to be 184,840 h-1. Ti0.95Cu0.05O1.95 catalyst coated on cordierite monolith enhanced the rate of thereaction compared to powder catalyst and made the handling and recycling of the catalyst very easy.

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