The equilibrium structure of thiophene by the combined use of electron diffraction, vibrational spectroscopy and microwave spectroscopy guided by theoretical calculations

The equilibrium molecular geometry of thiophene has been determined from a combination of gas-phase electron diffraction, vibrational and microwave da ta and ab initio and DFT calculations. The quadratic and cubic force consta nts of thiophene calculated theoretically and empirically improved by harmo nic scale factors were incorporated in the analysis in which equilibrium di stances and harmonic scale factors were refined simultaneously. The diffrac tion intensities were calculated by the use of first-order perturbation the ory. The commonly used r(a) distances and amplitudes of vibration were also estimated and found to agree reasonably well with those from an earlier in vestigation. Anharmonic phase shift parameters for all atom pairs and the v arious distance correction terms are presented. (C) 2001 Elsevier Science B .V. All rights reserved.