Searching blue-shifted O–H···Y hydrogen bond in CH3OH complexes with CF4, C2F2, OC, Ne, and He: a theoretical study

Abstract

The hydrogen-bonded structures of the CH3OH complexes with CF4, C2F2, OC, Ne, and He are designated as the starting points for geometry optimizations without and with counterpoise (CP) correction at MP2 level of theory with the basis sets 6-31+G*, 6-31++G**, and 6-311++G**, respectively. Tight convergence criteria are applied throughout all geometry optimizations in order to reduce the computational errors. According to the optimizations without CP correction, a blue-shifted O–H···Y (where Y = F, O, Ne, or He) hydrogen bond exists in all these five complexes. The magnitudes of blue shifts of ν(O–H) of the former four complexes with respect to that of CH3OH are reduced greatly when the polarization and diffuse functions of the hydrogen atoms are added (results from 6-31+G* versus those from 6-31++G**). However, for the complexes CH3OH–CF4 and CH3OH–C2F2, our optimizations using the CP corrections did not find the hydrogen-bonded structure to be a stationary point. The energy minimum of both the complexes corresponds to a non-hydrogen-bonded structure.