Does the molecular structure of CaH2 affect the dihydrogen bonding in CaH2•••HY (Y = CH3, C2H3, C2H, CN, and NC) complexes? A quantum chemistry study using MP2 and B3LYP methods

Second-order Moller-Plesset (MP2) and density functional theory (DFT) calculations have been carried out in order to investigate the structures and properties of dihydrogen-bonded CaH2 center dot center dot center dot HY (Y = CH3, C2H3, C2H, CN, and NC) complexes. Our calculations revealed two possible structures for CaH2 in CaH2 center dot center dot center dot HY complexes: linear (I) and bent (II). The bond lengths, interaction energies, and strengths for H center dot center dot center dot H interactions obtained by both MP2 and B3LYP methods are quite close to each other. It was found that the interaction energy decreases with increasing electron density at the Ca-H bond critical point. Atom-in-molecule (AIM) results show that for all of Ca-H center dot center dot center dot H-Y interactions considered here, the Laplacian of the electron density at the H.-H bond critical point is positive, indicating the electrostatic nature of these Ca-H center dot center dot center dot H-Y dihydrogen bonded systems.