Correlated ab initio harmonic frequencies and infrared intensities for furan, pyrrole, and thiophene

Equilibrium geometries, harmonic vibrational frequencies, and infrared intensities are calculated analytically at the second-order Moeller-Plesset level (MP2) with a DZP basis for the five-membered heterocyclic aromatics furan, pyrrole, and thiophene. The results are of an accuracy to show up misassignments in the original experimental interpretation of the spectra. They also give confidence that ab initio calculations including electron correlation and using flexible basis sets can describe accurately the quadratic part of the potential energy surface. For such systems, these ab initio studies will aid the spectroscopic determination of force constants.