A contribution to the structure determination of Ar-thiophene: the electric dipole moment

Employing pulsed molecular beam Fourier transform microwave spectroscopy (F TMW) an electric dipole moment of mu(T) = mu(a) = 0.5296(13) D was determin ed for thiophene, C4H4S from Stark effect measurements. The components of t he electric dipole moment along the a and b principal axis system of the Ar -thiophene complex were determined to be mu(a) = 0.01414(11)D and mu(b) = 0 .5279(13) D, and compared with the values yielded by ab initio calculations . The experimental and theoretical dipole moments combined with the calcula ted stabilization energies are only consistent with a structure having C-s symmetry in which the distance between S and the center of mass of the comp lex is 1.72 Angstrom and Ar is tilted away from S. (C) 1998 Elsevier Scienc e B.V. All rights reserved.