Microhydration of Phenyl Formate: Gas-Phase Laser Spectroscopy, Microwave Spectroscopy, and Quantum Chemistry Calculations

Abstract

Herein, we have investigated the structure of phenyl formate⋅⋅⋅water (PhOF⋅⋅⋅H2O) dimer and various non-covalent interactions present there using gas-phase laser spectroscopy and microwave spectroscopy combined with quantum chemistry calculations. Two conformers of PhOF⋅⋅⋅H2O (C1 and T1), built on the two cis/trans conformers of the bare molecule, have been observed in the experiment. In cis-PhOF, there is an nCO→urn:x-wiley:14394235:media:cphc202200330:cphc202200330-math-0001 interaction between the lone-pair orbital of the carbonyl oxygen atom and the π* orbital of the phenyl ring, which persists in the monohydrated C1 conformer of PhOF⋅⋅⋅H2O according to the NBO and NCI analyses. On the other hand, this interaction is absent in the trans-PhOF conformer as the C=O group is away from the phenyl ring. The C1 conformer is primarily stabilized by an interplay between O−H⋅⋅⋅O=C hydrogen bond and O−H⋅⋅⋅π interactions, while the stability of the T1 conformer is primarily governed by the O−H⋅⋅⋅O=C hydrogen bond. The most important finding of the present work is that the conformational preference of the PhOF monomer is retained in its monohydrated complex.