15min:

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 cloud of the ring (H- 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- 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- complex.