Prediction and characterization of halogen-hydride interaction in CunHn•••ClC2Z and CunH•••ClC2Z complexes (n=2-5; Z = H, F, CH3)

Halogen-hydride interactions between the lowest energy structure of Cu (n) H (n) and Cu (n) H clusters (n = 2-5) as halogen acceptor and ClC(2)Z (Z = H, F, CH3) as halogen donor have been investigated at the MP2/6-311++G(d,p) level of theory. Different approaches based on structural parameters, energetic analysis, shift in vibrational frequencies, and molecular electrostatic potential were used to characterize the resultant halogen-hydride bonds. Upon complexation, the Cl-C bonds tend to elongate, concomitant with red shifts of the Cl-C vibrational frequencies. Interaction energies of this type of halogen bonds vary from -2.34 to a maximum -7.38 kJ mol(-1). The calculated interaction energies were found to be increased in magnitude with increasing of the negative electrostatic potential at a point on the outer side of hydrogen atom of halogen acceptor units. Moreover, decomposition of the interaction energies reveals that the electrostatic interaction plays a main role in the formation of the complexes. The quantum theory of atoms in molecules analysis has also been applied to provide more insight into the nature and properties of these interactions. Our results indicate pure closed-shell interactions in these systems with similar characteristics to the conventional halogen bonds.