Probing microhydration induced effects on Carbonyl Compounds

Abstract

Characterizing the microhydration of organic molecules is a crucial step in understanding many phenomena relevant for the atmospheric, biological and industrial applications. However, its precise experimental and theoretical description remains a challenge. For four organic solutes containing a C=O bond, and included in the recent HyDRA challenge [Physical Chemistry Chemical Physics, 2022, 24, 11442-11454.], we propose a detailed study of the different monohydrate isomers and their properties. These are Cyclooctanone (CON), 1,3-Dimethyl-2-imidazolidinon (DMI), Methyl lactate (MLA), and 2,2,2-trifluoroacetophenone (TPH) molecules. As reported in the literature, the O-H elongation shift of the water molecule appears to be a good candidate for characterizing complexation induced effects. We also show that the C=O elongation shift and the UV-VIS spectroscopy can be used also, with confidence, for fully those purposes. Besides, we present a comparative analysis of the strengths of non-covalent interactions within these monohydrated complexes based on interpretative tools from quantum chemistry, including the topological analysis of the electron density ρ, the topological analysis of the electron pairing function, and the Core Valence Bifurcation Index (CVBI), which exhibits a close linear dependency upon ρ. Accordingly, a classification of intermolecular water - solute interactions is proposed.