Identification of conformational structures of 2-phenylethanol and its singly hydrated complex by mass selective high-resolution spectroscopy and ab initio calculations.

The flexible prototype molecule 2-phenylethanol (2-PE) and its singly hydrated complex have been investigated in a cold supersonic beam by a combination of high-resolution two-color R2PI spectroscopy and quantum chemistry ab initio calculations. The existence of two monomer structures separated by a high potential energy barrier, gauche and anti ones, was proven. Higher energy conformers are supposed to relax to the observed ones during the jet expansion process. We have identified the conformational structure of the complex between 2-PE and water, which corresponds to water binding to the most stable gauche conformer. No detectable structural changes of the host 2-PE molecule have been observed upon attachment of a single water molecule. A conformational relaxation mechanism is suggested also for the 2-PE x H2O complex.