Abstract

The dynamic and static dipole polarizabilities of 2-methythiophene (2MT) and 3-methylthiophene (3MT) molecules were investigated using refractometric and theoretical calculations. The experimental properties were studied within the Garito and Singer approach for dilute CCl4 and CH3CN solutions. The local field effects were tested with the Onsager and Lorentz local fields. The static dipole polarizabilities of 2MT and 3MT were obtained from extrapolation to zero frequency of the corresponding dispersion Cauchy-type curves, which gave a monotonic increase as a function of the squared frequency. The differences between these curves were analyzed as a function of the solvent effects and the local fields. The theoretical static properties were evaluated by using ab initio (Hartree-Fock) and density functional theory (DFT) (BLYP and B3LYP) methods with the 6-31 + G(d,p), 6-311 ++ G(3d,3p) and Sadlej basis sets. The dynamic polarizabilities were calculated with the time-dependent Hartxee-Fock (TDHF) approach and the 6-31 + G(d,p) and Sadlej basis sets. In order to make a comparison with the experimental results, the solvent effects were studied at the TDHF level in both CCl4 and CH3CN solvents and the Onsager model. The calculations were performed with fully optimized geometries. The experimental values of the static dipole polafizabilities of the 2MT and 3MT were determined as 1.129 x 10(-21) and 1.140 x 10(-21) esu, respectively, whereas the corresponding B3LYP/6-311 ++ G(3d,3p) values were 1.151 x 10(-21) and 1.139 x 10(-21) esu, respectively. Additionally, for the B3LYP/Sadlej method the corresponding values were 1.176 x 10(-21) and 1.174 x 10(-21) esu, respectively. In general, there was good agreement between the experimental and the DFr theoretical results. Copyright (C) 2002 John Wiley Sons, Ltd.