Electronic and vibrational spectroscopy of jet-cooled complexes of o-cyanophenol

Hydrogen-bonded complexes of o-cyanophenol (o-CNP) with a series of protic and non-protic solvents have been investigated in supersonic jet by means of laser-induced fluorescence excitation and dispersed emission spectroscopy. All the complexes exhibit a large red shift of the S0–S1 transition extending from −674 cm−1 for acetonitrile to −1321 cm−1 for the dimer of methanol. This shift is shown to correlate with the proton affinity of the protic solvents and has been related to the formation of cyclic hydrogen bond networks. For a non-protic solvent such as diethylether, the presence of a strong H bond has been confirmed by the study of the OH stretch using IR–UV double resonance spectroscopy. The low energy intermolecular vibrations observed in the cyclic complexes of o-CNP with H2O and CH3OH were assigned by comparing the experimental frequencies observed in the S0 and S1 states with the results of DFT calculations. The complexes with TEA undergo proton transfer as evidenced from the observation of the fluorescence attributable to the deprotonated form of o-CNP.