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.

    • Highly recyclable palladium ion substituted TiO2 as the versatile ligand-free catalyst for the selective oxidation of alcohols and the reduction of nitroarenes


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      A noble metal ionic catalyst, Ti0.97Pd0.03O1.97 is synthesized by the solution combustion method with an average crystal size of 5 nm. The robustness of the catalyst is explored in both alcohol oxidation and aromatic nitro reduction reactions. This catalyst is effective in the selective oxidation of primary alcohol to aldehyde. Efficient transformation of various alcohols to carbonyl compounds is achieved in a short reaction time. The reduction of diverse aromatic nitro compounds is carried out in the presence of NaBH4 and H2 as hydrogen sources. The solvent-free reduction is also carried out with a good yield. The present catalyst shows electivity in the nitro reduction more favorably in the presence of the carbonyl group also. The recycling is carried out by easily employing catalyst-coated cordierite monolith in oxidation and reduction reactions, up to 10 cycles.

      Synopsis: The Ti0.97Pd0.03O1.97 catalyst is synthesized by solution combustion method crystallizes in anatase phase with average crystallite size of 5 nm. This catalyst is highly active for the selective oxidation of alcohols and reduction of nitroarenes. The catalyst coated over cordierite monolith can be recycled even up to 10 cycles.

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