Herein, we have investigated the structure of phenyl formate⋅⋅⋅water (PhOF⋅⋅⋅H2 O) 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⋅⋅⋅H2 O (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 → 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⋅⋅⋅H2 O 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.
Keywords: UV/IR spectroscopy; hydrogen bond; jet spectroscopy; microhydration; microwave spectroscopy.
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