The importance of specific solvent–solute interactions for studying UV–vis spectra of light-responsive molecular switches

Abstract

Short-range interactions between solvents and molecular switches influence their structure, electronic transitions, and stability. The explicit solvent interactions between water and N′-[1-(2-hydroxyphenyl)ethyliden]isonicotinoyl hydrazone, as a representative of the light-responsive molecule, were investigated by quantum chemical techniques, density functional theory, natural bond orbital, and quantum theory of atoms in molecules. On the basis of the preliminary spectra obtained with the polarizable continuum solvent model, the most probable groups for the formation of specific interactions were determined. The experimental UV-vis spectrum was reproduced with the addition of five molecules of water and interactions between solvent and solute are discussed in detail. The number of water molecules was reduced to one and it was proven that this can be sufficient for the reproduction of the experimental spectra if solvent molecules are placed in the right position. Quantum theory of atoms in molecules analysis gave better insight into the change of bond critical point parameters with distance, especially for the formed hydrogen bonds.