Internal electric fields in methanol [MeOH]2–6 clusters

Abstract

Water and methanol are well known solvents showing cooperative hydrogen bonding, however the differences in the hydrogen bonding pattern in water and methanol are due to the presence of the methyl group in methanol. The presence of the methyl group leads to formation of C–H⋯O hydrogen bonds apart from the usual O–H⋯O hydrogen bonds. The electric fields evaluated along the hydrogen bonded donor OH and CH groups reveal that the C–H⋯O hydrogen bonds can significantly influence the structure and energetics (by about 20%) of methanol clusters. A linear Stark effect was observed on the hydrogen bonded OH groups in methanol clusters with a Stark tuning rate of 3.1 cm⁻¹ (MV cm⁻¹)⁻¹ as an average behaviour. Furthermore, the Stark tuning of the OH oscillators in methanol depends on their hydrogen bonding environment wherein molecules with the DAA motif show higher rates than the rest. The present work suggests that the OH group of methanol has higher sensitivity as a vibrational probe relative to the OH group of water.