Infrared Spectrum and UV-Induced Photochemistry of Matrix-Isolated 5-Methoxy-1-Phenyl-1H-Tetrazole

GOMEZ ZAVAGLIA, ANDREA, I. REVA, L. FRIJA, M.L.CRISTIANO AND R. FAUSTO

Coimbra, Portugal

Congreso; 8th Photochemistry Meeting of the Portuguese Chemical Society; 2005

Sociedad Portuguesa de Quimica

The molecular structure, vibrational spectra and photochemistry of 5-methoxy-1-phenyl-1H-tetrazole (5MPT) were studied by matrix isolation infrared spectroscopy and DFT(B3LYP)/6-311++G(d,p) calculations. According to the calculations, only one double degenerated-by-symmetry minimum exists in the ground state PES of the compound. In this structure, the dihedral angle between the two rings (phenyl and tetrazole) is ca. 30º, whereas the methoxylic group stays nearly in the plane of the tetrazole ring. In consonance with the theorectical predictions, only one molecular species was experimentally observed in the as-deposited argon matrices. Theoretical calculations were also used to help assignment of the experimental spectrum of the compound, the calculated spectrum showing a very good agreement with the experimental data. In situ UV-irradiation (l > 235 nm) of the matrix-isolated 5MPT induced unimolecular decomposition of the compound, which led mainly to production of methylcyanate and phenylazide, this latter further reacting to yield, as final product, 1-aza-1,2,4,6-cycloheptatetraene. 3-methoxy-1-phenyl-1H-diazirene was also observed experimentally as minor product, resulting from direct elimination of molecular nitrogen from 5MPT.