Empirical corrections for anharmonic zero-point vibrations of hydrogen and deuterium in geometric hydrogen bond correlations

Abstract

In this paper, empirical corrections for anharmonic ground-state vibrations of hydrogen and deuterium in the hydrogen bridges A–L⋯B, L=H, D are introduced into the geometric hydrogen bond correlation analysis based on the empirical Pauling valence bond orders. The method is verified using the examples of the hydrogen bonded anions in [(CO) 5Cr–CN⋯H⋯NC–Cr(CO) 5] − As(Ph) 4 + ( 1h), in [(CO) 5Cr–CN⋯H⋯NC–Cr(CO) 5] − N( n-propyl) 4 + ( 2h), in the model system [CN⋯H⋯NC] − Li + ( 3h), and their deuterated isotopologs ( 1d, 2d and 3d) studied previously by dipolar NMR and theoretical methods by H. Benedict et al. [J. Am. Chem. Soc. 120 (1998) 2939]. The new corrections are able to describe isotope effects on hydrogen bond geometries from the weak to the strong hydrogen bond regime, taking into account single and double-well situations.