Exploring the next step in micro-solvation of CO in water: Infrared spectra and structural calculations of (H₂O)₄–CO and (D₂O)₄–CO

We extend studies of micro-solvation carbon monoxide by a combination high-resolution IR spectroscopy and ab initio calculations. Spectra the (H2O)4-CO (D2O)4-CO pentamers are observed in C-O stretch fundamental region (~2150 cm-1). The H2O containing spectrum is broadened predissociation, but that D2O sharp, enabling detailed analysis which gives precise band origin rotational parameters. Ab calculations employed to confirm assignment (water)4-CO determine structure, geometry (water)4 fragment cyclic ring very similar isolated water tetramer. CO located "above" plane, with partial hydrogen bond between C atom one "free" protons (deuterons) Together previous results on D2O-CO, (D2O)2-CO, (D2O)3-CO, this represents probe four initial steps solvation at high resolution.