• P K Singh

      Articles written in Journal of Chemical Sciences

    • Boron complexes of sulphur containing Schiff bases derived by the condensation of S-methyl or S-benzyl dithiocarbazate with β-diketones

      P K Singh J P Tandon

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      Tetra-coordinated boron derivatives, (EtO)B(DTZ) and (DTZH)B(DTZ), (where DTZ−− and DTZ represent the anions of the Schiff base DTZH2) have been synthesized by 1:1 and 1:2 molar reactions of triethoxyborane with bibasic tridentate Schiff bases, derived by the equimolar condensation of S-methyl or S-benzyldithiocarbazate with acetyl acetone or benzoyl acetone. Further 1:1 derivatives have been shown to undergo replacement reactions witht-butyl alcohol, showing thereby the labile nature of the ethoxy group. Based on infrared and proton magnetic resonance spectral studies and monomeric nature, suitable structures have been assigned to these derivatives.

    • Potentiometric and spectrometric study: Copper(II), nickel(II) and zinc(II) complexes with potentially tridentate and monodentate ligands

      R N Patel Nripendra Singh R P Shrivastava K K Shukla P K Singh

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      Equilibrium and solution structural study of mixed-metal-mixed-ligand complexes of Cu(II), Ni(II) and Zn(II) with L-cysteine, L-threonine and imidazole are conducted in aqueous solution by potentiometry and spectrophotometry. Stability constants of the binary, ternary and quaternary complexes are determined at 25 ±1°C and in I= 0.1 M NaClO4. The results of these two methods are made selfconsistent, then rationalized assuming an equilibrium model including the species H3A, H2A, A, BH, B, M(OH), M(OH)2, M(A), MA(OH), M(B), M(A)(B), M2(A)2(B), M2(A)2(B-H), M1M2(A)2(B) and M1M2(A)2(B-H) (where the charges of the species have been ignored for the sake of simplicity) (A = L-cysteine, L-threonine, salicylglycine, salicylvaline and BH = imidazole). Evidence of the deprotonation of BH ligand is available at alkalinepH. N1H deprotonation of the bidentate coordinated imidazole ligand in the binuclear species atpH > 70 is evident from spectral measurements. Stability constants of binary M(A), M(B) and ternary M(A)(B) complexes follow the Irving-Williams order.

    • An investigation on structural, vibrational and nonlinear optical behavior of 4b,9b-dihydroxy-7,8-dihydro-4bH-Indeno[1,2-b] Benzofuran-9,10(6H,9bH)-dione: A DFT study

      Tanveer Hasan Sayed Hasan Mehdi Raza Murad Ghalib P K Singh Neeraj Misra

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      A detailed theoretical quantum chemical study on 4b,9b-dihydroxy-7,8-dihydro-4bH-indeno[1,2-b] benzofuran-9,10(6H,9bH)-dione (Dihydroxy-Dihydro-Indeno-Benzofuran-Dione) has been discussed. The structure of the title molecule has been optimized and the structural parameters have been calculated by DFT/B3LYP method with 6-311++G(d,p) basis set. The fundamental vibrational wavenumbers as well as their intensities were calculated and excellent agreement between observed and calculated wavenumbers has been achieved and was interpreted in terms of potential energy distribution analysis. The electronic properties such as HOMO and LUMO energies and associated frontier energy band gap were calculated. Thermodynamical parameters along with the nonlinear optical (NLO) behavior of the title molecule are also discussed. The lower value of frontier orbital energy gap and a higher value of dipole moment suggest that the title compound is highly reactive. The NLO behavior of the title compound has been achieved by dipole moment, polarizability and first static hyperpolarizability. The large value of hyperpolarizability 𝛽total, indicates that the title molecule may serve as a good NLO material. The theoretical results were found to be in coherence with the measured experimental data.

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