• Issue front cover thumbnail

      Volume 120, Issue 4

      July 2008,   pages  355-424

    • Synthesis, photoluminescence and electrochemical properties of 2,7-diarylfluorene derivatives

      Neeraj Agarwal Pabitra K Nayak N Periasamy

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      A new class of highly fluorescent 9,9'-bis-(alkyl)-2,7-diarylfluorene having electron withdrawing or electron donating groups on the 𝑝-phenyl positions were synthesized and characterized. The highly luminescent fluorene derivatives, 1-6 showed blue emission (376-416 nm), narrow FWHM (∼ 50 nm), high quantum yield ($\phi_{\text{F}} = 0.12-0.87$) and short fluorescence lifetimes, $\tau_{\text{F}} = 0.23-1.14$ ns. The HOMO levels of 9,9'-bis-(alkyl)-fluorene were tuned by the p-substituents at 2,7-phenyl group. Hammett correlation with $E_{\text{HOMO}}$ of these new molecules provides an effective tool to predict the HOMO level of similar molecules prior to the synthesis. These data indicate that they are useful as emitting materials for organic light emitting devices, OLEDs.

    • Phosphorus-nitrogen compounds: Part 15. Synthesis, anisochronism and the relationship between crystallographic and spectral data of monotopic spiro-crypta phosphazenes

      Nuran Asmafi̇li̇z Eli̇f Ece İl Ter Zeynel Kiliç Tuncer Hökelek Ertan Şahin

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      The reactions of hexachlorocyclotriphosphazatriene, N3P3Cl6, with N2O2-donor type coronands, Ph2[OR1O][CH2NHR2NHCH2] [R1 = (CH2)3, R2 = (CH2)3 (1), R1 = (CH2)3, R2 = (CH2)4 (2), R1 = (CH2)4, R2 = (CH2)4 (3)], give monotopic spiro-crypta phosphazene architectures, N3P3Cl4{Ph2 [OR1O][CH2NR2NCH2]} [R1 = (CH2)3, R2 = (CH2)3 (4), R1 = (CH2)3, R2 = (CH2)4 (5) and R1 = (CH2)4, R2 = (CH2)4 (6)], respectively. The reaction of 4 with excess pyrrolidine leads to the formation of geminal N3P3Cl2(C5H5N)2{Ph2[O(CH2)3O] [CH2N(CH2)3NCH2]} (7). The 31P-NMR spectra of 5 and 6 indicate that these compounds have anisochronism. The structures of 5, 6 and 7 were investigated by X-ray crystallography. For 7, the sums of the bond angles around the N atoms were 348.6(2)° and 349.7(2)° indicating that the N atoms have pyramidal configurations and are stereogenic. The relationship between the chemical shift values $\delta P_{\text{(spiro)}}$ and the $\Delta(P-N)$ (electron density transfer parameters) of 4, 5, 6, 7 and the analogous compounds as well as the relationship between the $\Delta(\delta P)$ values and the above mentioned $\Delta(P-N)$ are presented respectively. In addition, the relationship between the endocyclic NPN bond angles of these compounds and the 31P-NMR chemical shifts of the spiro-phosphorus atoms were investigated. The spectroscopic and structural investigations of the compounds were made by elemental analyses, MS, FTIR, one-dimensional 1H-, 13C-, 31P-NMR, DEPT and two-dimensional COSY, HETCOR, HMBC, homo- and heteronuclear correlation techniques.

    • Coordination equilibria in the complex formation of guanylurea with CuII: Formation and stability of binary CuII-guanylurea and ternary CuII-guanylurea-glycinate complexes

      Tannistha Roy Barman G N Mukherjee

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      Combined pH-metric and spectrophotometric investigations on the complex formation equilibria of CuII with guanylurea (H$_2^1$NC(=O) 2NH.C(=3NH) 4NH2), hereafter, GuH, in the absence and in the presence of glycine (GlyH), in aqueous solution indicates variety of binary and mixed-ligand complexes: Cu(Gu)+, Cu(Gu)(OH); Cu(Gu)2, Cu(Gu-H)(Gu)-, Cu(Gu-H)$_2^{2-}$, Cu(Gu-H)(Gu-2H)$^{3-}$; Cu(Gly)+, Cu(Gly) (OH); Cu(Gly)(Gu); Cu(Gly)(Gu-H)-, Cu(Gly)(Gu-2H)2-; (Gly)Cu(Gu)Cu(Gly)+, (Gly)Cu(Gu-H)Cu(Gly) and (Gly)Cu(Gu-2H)Cu(Gly)-. At pH < 6, guanylurea anion (Gu-) acts as a [(C=O), 3N-] or [=1NH, 3N-] bidentate ligand and above pH 7 it is transformed through a coordination equilibrium into a (=1N-, =3N-) bidentate ligand, similar to biguanide dianion. Occurrence of dinuclear complex species, (Gly) Cu(Gu)Cu(Gly)+, in the complexation equilibria, indicates bridging double bidentate [(1NH2, 3N-), (C=O, 4NH2)] and/or [(1NH2, 4NH2), (C=O, 3N-)] chelation by Gu- ion in an isomeric equilibrium. Above pH 6.5, the dinuclear complex decomposes mostly to the mononuclear species, Cu(Gly)(OH) and Cu(Gu)(OH) and only partly deprotonates to (Gly)Cu(Gu-H)Cu(Gly) and (Gly)Cu(Gu-2H)Cu(Gly)-. Electronic spectral shifts, with change of pH have been correlated with the possible modes of coordination of guanylurea species.

    • High stereoselective cyclopropanation reaction of 3-acylcoumarins with 𝛼-bromoketones at room temperature

      Qin Zhao Min Chen Hao-Hao Hui De-Bing She Ming-Yu Yang Guo-sheng huang

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      Reaction of 3-acylcoumarins with 𝛼-bromoketones in the presence of a base give the cyclopropane derivatives in good stereoselectivity and moderate yield. The reaction was carried out at room temperature in mixed solvents without exclusion of moisture or air.

    • Assessing ligand efficiencies using template-based molecular docking and Tabu-clustering on tetrahydroimidazo-[4,5,1-jk][1,4]-benzodiazepin-2(1H)-one and -thione (TIBO) derivatives as HIV-1RT inhibitors

      Nitin S Sapre Swagata Gupta Neelima Sapre

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      A template-based flexible docking simulation followed by `Tabu-clustering’ was performed on a series of 38 TIBO derivatives as HIV-1 reverse transcriptase (HIV-1 RT) inhibitors. Four different templates of the Cl-TIBO (1-REV) were created and used as reference templates for docking and aligning. On the basis of the optimal conformation of the ligands, when fitting to the template, the respective scoring functions were obtained; different ligand efficiencies were evaluated and analysed. Statistical modelling using artificial neural network (ANN: $r^2 = 0.922$) and multiple linear regression method (MLR: $r^2 = 0.851$) showed good correlation between the biological activity, binding affinity, and different ligand efficiencies of the compounds, which suggest the robustness of the template-based binding conformations of these inhibitors. Our studies suggest that, template-based docking followed by ‘Tabuclustering’ will give a better alignment of inhibitors with respect to the crystal coordinates and enhance the docking efficiency. Also, our study indicates that scoring functions based on 3D symmetry analysis along with heavy atoms count serve as a valuable tool for estimating the efficiency of the ligands. Thus, this is a novel method based on heavy atoms count predicting the binding affinity of the TIBO group of inhibitors, so that their therapeutic utility can be enhanced.

    • Surface enhanced Raman spectra of the organic nonlinear optic material: Methyl 3-(4-methoxy phenyl)prop-2-enoate

      D Sajan I Hubert Joe V S Jayakumar Jacek Zaleski

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      The surface geometry of methyl 3-(4-methoxy phenyl)prop-2-enoate molecule was studied by analysis of the SERS spectra adsorbed on silver colloid surfaces. For a reliable analysis of the SERS spectrum, we also performed density functional theoretical calculations. The absence of a C-H stretching vibrations and the observed C-H out-of-plane bending modes suggest that the MMP molecule may be adsorbed in a flat on orientation to the surface. The SERS spectral studies predict a tilted orientation of ethylenic bridge with respect to the phenyl ring.

    • Hydrolytic cleavage of bis(𝑝-nitrophenyl) phosphate by Schiff base MnIII complexes containing morpholine pendants in Gemini 16-6-16 micelles

      Weidong Jiang Bin Xu Junbo Zhong Jianzhang Li Fuan Liu

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      Catalytic efficiency of two Schiff base manganese(III) complexes toward the hydrolysis of bis(𝑝-nitrophenyl) phosphate (BNPP) was evaluated in a micellar media formed by bis(hexadecyldimethylammonium) hexane bromide (abbr.16-6-16, 2Br-) at $25^\circ$C. Effects of various reaction conditions on the hydrolysis of BNPP were systematically investigated. The observations obtained indicate that the two Mn(III) catalysts can efficiently promote hydrolysis of BNPP with a six order of magnitude rate enhancement relative to the background rate constant ($k_0$). Different structures of the two complexes lend to their distinguishing activities each other. Furthermore, rates of BNPP hydrolysis in Gemini 16-6-16 micellar medium are much higher than that in hexadecyltrimethylammonium bromide (CTAB) and 𝑛-lauroylsarcosine sodium (LSS) micelles.

    • Microdetermination of human serum albumin by differential pulse voltammetry at a L-cysteine modified silver electrode

      Liyuan Lu Yanqin Zi Hongling Wang

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      A simple and highly sensitive electrochemical method for the determination of human serum albumin (HSA) using differential pulse voltammetry (DPV), based on a silver electrode modified with a self-assembled monolayer of L-cysteine, was developed. L-cysteine can be modified onto a silver electrode by covalent bonding through the sulfur to give stable and long-lived chemical electrodes. This electrode showed good sensitivity, selectivity, reproducibility and time stability in the determination of trace amounts of HSA by DPV technique. The detection limit can be as low as $4 \times 10^{-17}$ mol/L. The optimum conditions for the determination were carefully investigated. This method had been applied to the determination of HSA in human serum samples. The results were in agreement with those given in standard method.

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