Molecular Electrostatic Potential as Reactivity Index in Hydrogen Bonding: Ab Initio Molecular Orbital Study of Complexes of Nitrile and Carbonyl Compounds with Hydrogen Fluoride

Abstract

Ab initio molecular orbital calculations at the HF/6-31+G(d,p) level were used to investigate the hydrogen bonding between hydrogen fluoride and two series of molecules, nitrile and carbonyl compounds of the type R−CN and R−CHO, respectively, where R= −H, −OH, −SH, −OCH3, −NH2, −NO2, −C⋮N, −F, −Cl, −CH3, and −CF3. Geometry optimization and vibrational frequency calculations at the optimized geometry were performed for isolated and hydrogen-bonded systems. The estimated energies of hydrogen-bond formation were corrected for zero-point vibrational energy and basis set superposition error (including the relaxation correction). Linear relations between the energy of hydrogen-bond formation (ΔE) and the H−F stretching frequency shift (ΔνHF) are obtained for the two series studied. Linear dependencies are also found between ΔE and the change of H−F bond length (ΔrHF). An excellent linear dependence is found between ΔER-CN and the ab initio calculated molecular electrostatic potential at the nitrile nitrogen (VN...