Correlation of the bond-length change and vibrational frequency shift in model hydrogen-bonded complexes of pyrrole

Abstract

An MP2 computational study of model hydrogen-bonded pyrrole⋯YZ (YZ=NH3, NCH, BF, CO, N2, OC, FB) complexes was undertaken in order to examine the variation of the NH bond length change and its associated vibrational frequency shift. The chemical hardness of Y, as well as the YZ dipole moment, were found to be important parameters in modifying the bond length change/frequency shift. The basis set effect on the computed properties was also assessed. A perturbative model, which accurately reproduced the ab initio NH bond length changes and frequency shifts, was useful in rationalizing the observed trends.