Infrared and ab Initio Studies on 1,2,4,5-Tetrafluorobenzene Clusters with Methanol and 2,2,2-Trifluoroethanol:  Presence and Absence of an Aromatic C−H···O Hydrogen Bond

The (1:1) clusters of 1,2,4,5-tetrafluorobenzene (TFB) with methanol and with 2,2,2-trifluoroethanol (TFE) were studied both experimentally and computationally. Through use of fluorescence-detected infrared spectroscopy, the (1:1) clusters were identified in supersonic jets. Intermolecular interactions in the clusters were characterized by the spectral shifts of the aromatic C−H stretching modes in the TFB moiety owing to the cluster formation. The molecular structures, stabilization energies, and vibrational frequencies of the clusters were computed at the MP2/6-31+G* level. Both computational and experimental data indicate that an aromatic C−H···O hydrogen bond is present in the TFB−methanol cluster, while it is absent in the TFB−TFE cluster.