Abstract: The optimized structures and binding energies of a series of C6H5—H…X hydrogen-bonded complexes involving H2O, HCOH, NH3, CH2NH and HCN as proton acceptors were determined at B3LYP/6-311+G(3df, 2p) level. The calculated results showed that the binding energies of C6H5—H…X complexes were dependent on the nature of the proton-accepting groups. The contributions of π-bond, double-bond, triple-bond to the hydrogen bonds, and the
interaction energies between lone-pair electrons and the C—H antibond were discussed in detail by natural population analysis (NPA) and natural bond orbital analysis (NBO).

Key words: C6H5—H…X system, Hydrogen bond, Density functional theory, NPA, NBO