A DFT study on radical-cationic methanol clusters: Structure, bonding and H-transfer

Abstract

Radical-cationic methanol clusters (CH3OH) +n, n = 2–5, are studied in the gas phase and solvent methanol using hybrid B3LYP, CAM-B3LYP and BHandHLYP exchange-correlation functionals. The CAM-B3LYP predictions are the most consistent. Ionization of parental neutral rings and chains yields distonic radical cations with spin residing on the CH3O link. Higher energy OO hemibonded structures are also located. The intra-cluster H-transfer from the methyl group of the CH3OH-terminus of the protonated moiety to the O-atom of the CH3O terminus in chain radical cations leads to the lowest-energy distonic isomers with the CH2OH terminus. The CAM-B3LYP activation enthalpies for this reaction in the gas phase are 9.5, 11.1, 13.7, and 17.1 kcal/mol for n = 5, 4, 3, 2, respectively. The inter-cluster H-transfer from the CH3O terminus to a neutral methanol cluster occurs spontaneously, with formation of a protonated cluster weakly bound to the radical cluster. The protonated cluster may serve as a proton carrier.