Molecular Structure, Vibrational Spectra and Photochemistry of 1-Phenyl-4H-Tetrazolone Isolated in Solid Argon

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

Oporto, Portugal

Congreso; 7ª Meeting of Physical-Chemistry. Sociedade Portuguesa de Química; 2005

Sociedad Portuguesa de Quimica. División Fisicoquímica

Tetrazoles have drawn the attention of many people due to their important practical applications in different human activities (e.g., medicine and agriculture). In this work, 1-phenyl-4H-tetrazolone (PT) has been studied by FT-IR matrix isolation spectroscopy and theoretical methods. PT is a planar molecule that belongs to the Cs symmetry point group. It has 48 fundamental vibrations, being all active in the infrared. Matrix-isolated monomers of PT give rise to an IR spectrum that fits nicely the calculated spectrum, obtained at the B3LYP/6-3111++G(d,p) level of theory. In situ UV-irradiation (l > 235 nm) of the matrix induces four main photochemical processes, all of them involving the tetrazole ring cleavage: (1)             Molecular nitrogen loosing with production of 1-phenyl-diaziridin-3-one. This compound can then react by two different pathways: the first one leads to production of 1-aza-1,2,4,6-cycloheptatetraene and cyanic acid; the second one, to phenyldiazene and CO. (2)             Cleavage of C5-N1 and N3-N4 tetrazole ring bonds, with production of phenylazide and isocyanic acid. These primary photoproducts can then rearrange to give 1-aza-1,2,4,6-cycloheptatetraene and cyanic acid, respectively. (3)             Cleavage of N1-N2 and N4-C5 tetrazole ring bonds, with production of phenylisocyanate and azide. The first product can then rearrange to give phenylcyanate. (4)             CO expulsion, originating phenyltetrazete, which can then loose molecular nitrogen, giving rise to phenyldiazene.