JAY C. AMICANGELO, NATALIE C. ROMANO AND GEOFFREY R. DEMAY, School of Science, Penn State Erie, Erie, PA 16563.

Matrix isolation infrared spectroscopy was used to characterize a 1:1 complex of methanol (CH3OH) with benzene (C6H6). Co-deposition experiments with CH3OH and C6H6 were performed at 17 - 20 K using nitrogen and argon as the matrix gases. New infrared bands attributable to the CH3OH-C6H6 complex were observed near the O-H and C-O stretching vibrations of CH3OH and near the hydrogen out-of-plane bending vibration of C6H6. The initial identification of the new infrared bands observed was established by performing a conentration study (1:200 to 1:2000 S:M ratios), by comparing the co-deposition spectra with the spectra of the individual monomers, by matrix annealing experiments, and by performing experiments using isotopically labeled methanol (CD3OD) and benzene (C6D6). Quantum chemical calculations were also performed for the CH3OH-C6H6 complex using density functional theory and ab initio methods. Two stable minima were found for the complex: one in which the CH3OH is above the C6H6 ring with the hydroxyl hydrogen interacting with the pi cloud of the ring (H- pi complex) and the other in which the CH3OH is in the plane of the C6H6 ring with the hydroxyl oxygen interacting with one of the C-H bonds of the ring (CH-O complex). Comparing the calculated shifts of the vibrational frequencies for both complexes to the observed experimental frequency shifts, it is found that the H- pi complex is in best agreement with the experimental shifts in both magnitude and direction. Therefore, it is concluded that the geometry of the CH3OH-C6H6 complex observed in the matrix isolation experiments is the H- pi complex.