Binding energies of micro-hydrated carbohydrates: measurements and interpretation

Abstract

The strength of the interaction between three monosaccharides (O-phenyl-β-D-gluco-, β-D-galacto- and α-D-mannopyranoside) and a single water molecule has been investigated experimentally in the gas phase by means of 2-colour UV-UV ionisation and dissociation threshold measurements. Their binding energies have also been calculated using dispersion corrected DFT methods and the resolution of identity approximation. The calculated and experimental relative binding energies are in good correspondence at all considered levels of theory, and the RI-B97D+disp/TZVPP level of theory in particular, provides very good agreement with a considerable reduction in computational time. Although these systems experience some conformational changes upon photo-ionisation, the experimental measurements lead to reliable estimates of the binding energies of the different conformers of the monosaccharide–water complexes and their relative values reflect their structural differences.