It is generally assumed that hydrogen-bonded complexes are less stable in solvents than in the gas phase and that their stability decreases with increasing solvent polarity. This assumption is based on the size of the area available to the solvent, which is always smaller in the complex compared to the subsystems, thereby reducing the solvation energy. This reduction prevails over the amplification of the electrostatic hydrogen bond by the polar solvent. In this work, we show, using experimental IR spectroscopy and DFT calculations, that there are hydrogen-bonded complexes whose stability becomes greater with increasing solvent polarity. The explanation for this surprising stabilization is based on the analysis of the charge redistribution in the complex leading to increase of its dipole moment and solvation energy. Constrained DFT calculations have shown a dominant role of charge transfer over polarization effects for dipole moment and solvation energy.

Institute of Organic Chemistry and Biochemistry Czech Academy of Sciences Flemingovo Námĕstí 542 2 16000 Prague Czech Republic

IT4Innovations VŠB Technical University of Ostrava 17 listopadu 2172 15 70800 Ostrava Poruba Czech Republic

Regional Centre of Advanced Technologies and Materials Czech Advanced Technology and Research Institute Palacký University Křížkovského 511 8 77900 Olomouc Czech Republic

Citace poskytuje Crossref.org

Striking Impact of Solvent Polarity on the Strength of Hydrogen-Bonded Complexes: A Nexus Between Theory and Experiment