Bond dissociation energies and equilibrium structures of Cu+(MeOH)x, x = 1-6, in the gas phase: competition between solvation of the metal ion and hydrogen-bonding interactions

The solvation of Cu+ by methanol (MeOH) was studied via examination of the kinetic energy dependence of the collision-induced dissociation of Cu+(MeOH)x complexes, where x = 1-6, with Xe in a guided ion beam tandem mass spectrometer. In all cases, the primary and lowest-energy dissociation channel observed is the endothermic loss of a single MeOH molecule. The primary cross section thresholds are interpreted to yield 0 and 298 K bond dissociation energies (BDEs) after accounting for the effects of multiple ion-neutral collisions, kinetic and internal energy distributions of the reactants, and lifetimes for dissociation. Density functional theory calculations at the B3LYP/6-31G* level are performed to obtain model structures, vibrational frequencies, and rotational constants for the Cu+(MeOH)x complexes and their dissociation products. The relative stabilities of various conformations and theoretical BDEs are determined from single-point energy calculations at the B3LYP/6-311+G(2d,2p) level of theory using B3LYP/6-31G*-optimized geometries. The relative stabilities of the various conformations of the Cu+(MeOH)x complexes and the trends in the sequential BDEs are explained in terms of stabilization gained from sd hybridization, hydrogen-bonding interactions, electron donor-acceptor natural bond orbital stabilizing interactions, and destabilization arising from ligand-ligand repulsion.