Molecular recognition in the gas phase. Dipole-bound complexes of benzonitrile with water, ammonia, methanol, acetonitrile, and benzonitrile itself.

Described herein are the high resolution fluorescence excitation spectra of 1 : 1 complexes of benzonitrile with water, ammonia, methanol, acetonitrile, and benzonitrile itself in the gas phase. Analyses of these spectra yield the equilibrium geometries of each species in both the ground and excited electronic states, and therefore provide information about the intermolecular interactions that are responsible for holding them together, in the absence of perturbing solvent molecules. In all cases, the determined structure corresponds to the one expected on the basis of interacting dipole moments; in some cases, significant internal motions of one component relative to the other, leading to a time-varying dipole field, also has been observed.