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Lithium-7 NMR and ab initio Calculation Studies of Complexation of Li+ Ion with 12-Crown-4, Benzo-12-crown-4, 15-Crown-5, Benzo-15-crown-5, and Dibenzo-15-crown-5 in Binary Nitromethane-Acetonitrile Mixtures

Shamsipur M., Alizadeh N., Rofouei M. K., Alizadeh K.

Polish Journal of Chemistry

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2007

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Vol. 81, nr 10

1743-1743

EN

Complexes of 12-crown-4 (12C4), benzo-12-crown-4 (B12C4), 15-crown-5 (15C5), benzo-15-crown-5 (B15C5) and dibenzo-15-crown-5 (DB15C5) with Li+ ion were investigated by lithium-7 NMR in a number of nitromethane (NM)-acetonitrile (AN) binary mixtures. In all cases, the exchange between the free and complexed lithium ionwas fast on the NMR time scale and a single population average resonance was observed. Both 1:1 and 2:1 (sandwich) complexeswere observed between lithium ion and 12C4 and B12C4 in pure nitromethane solution. Stepwise formation constants of the 1:1 and 1:2 (metal/ligand) complexes were evaluated from computer fitting of the NMR mole ratio data to equations which relate the observed metal ion chemical shifts to formation constants. There is an inverse linear relationship between the logarithms of the stability constants and the mole fraction of acetonitrile in the solvent mixtures. The stability of the complexes varies inversely with the Gutmann donor number of the solvent. The stability order of the complexes was found to be 15C5.Li+> B15C5.Li+> DB15C5.Li+> 12C4.Li+ > B12C4.Li+. The optimized structures of the free ligands and their 1:1 and 2:1 complexes with Li+ ionwere predicted by ab initio theoretical calculations using theGaussian 98 software, and the results are discussed.

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Electrochemical and Computational Studies of Some 9,10-Anthraquinone Derivatives in Acetonitrile Solution

Shamsipur M., Mohammadi T., Alizadeh N., Sharghi H., Nichols R.

Polish Journal of Chemistry

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2005

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Vol. 79 / nr 8

1379-1388

EN

The electrochemical behavior of some recently synthesized 9,10-anthraquinone derivatives on Au electrode in acetonitrile was investigated. In the absence of proton donors, the anthraquinones reduced in two successive one-electron steps. The first step is reversible or nearly reversible, while the second step is quasi-reversible. The influence of molecular structure on the reduction potential is addressed. The diffusion coefficients of the anthraquinone derivatives were determined from chronoamperometry and rotating disk electrode measurements. The heterogeneous electron transfer rate constants and charge transfer coefficients were evaluated from rotating disk voltammetry measurements. An ab-initio quantum mechanical method was carried out at the DFT-B3LYP level to compute the electrode's formal potentials for the four anthraquinones AQ1-AQ4 in acetonitrile solution. A nice linear relationship was observed between the theoretically predicted values and experimentally determined formal electrode potentials of the 9,10-anthraquinone derivatives.

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Synthesis of a new naphthol-derivate salen and spectrophotometric study of the thermodynamics and kinetics of its complexation with copper(II) ion in binary dimethylsulfoxide-acetonitrile mixtures

Alizadeh N., Ershad S., Naeimi H., Sharghi H., Shamsipur M.

Polish Journal of Chemistry

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1999

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vol. 73 nr 6

915-925

EN

A synthetic procedure has been developed for the preparation of new salen (2,2'-[1,2-ethanediyl bis(nitriloethylidyne)]bis(1-naphthalenol). The thermodynamics and kinetics of complexation reaction between the new salen and Cu2+ ion were investigated spectrophotometrically in different dimethylsulfoxide-acetonitrile mixtures. Formation constant of the resulting 1:1 complex was determined from the absorbance-mole ratio data and found to increase with increasing acetonitrile content of the solvent mixtures. Enthalpy and entropy data for complexation were determined from the temperature dependence of the formation constant. In all solvent mixtures, the salen-copper complex is entropy stabilized but enthalpy destabilized. Order of reaction, rate constants and activation parameters for the complexation reaction in different solvent mixtures were also investigated. The Arrhenius plots showed a distinct isokinetic temperature at about 88 oC, at which the reaction rate is approximately independent of the solvent composition. Activation parameters are strongly solvent dependent.