Triplet States of Tetrazoles, Nitrenes, and Carbenes from Matrix Photolysis of Tetrazoles, and Phenylcyanamide as a Source of Phenylnitrene Manabu Abe Didier Bégué Hugo Santos Silva Alain Dargelos Curt Wentrup 10.1021/acs.jpca.8b06960.s001 https://acs.figshare.com/articles/journal_contribution/Triplet_States_of_Tetrazoles_Nitrenes_and_Carbenes_from_Matrix_Photolysis_of_Tetrazoles_and_Phenylcyanamide_as_a_Source_of_Phenylnitrene/7053599 Photolysis of 1- and 5-aryltetrazoles at 5–10 K using a 266 nm laser immediately generates their triplet excited states, which are characterized by their electron spin resonance (ESR) spectra with zero-field splitting parameters <i>D</i> = 0.12–0.13 cm<sup>–1</sup> and <i>E</i> = 0.002–0.008 cm<sup>–1</sup>. Further photolysis of all of the aryltetrazoles affords arylnitrenes (<i>D</i> ≅ 1 cm<sup>–1</sup>), and in the case of 5-aryltetrazoles also arylcarbenes (<i>D</i> ≅ 0.5 cm<sup>–1</sup>). The formation of arylnitrenes from 5-aryltetrazoles, where no aryl–N bond is present, is explained by the photochemical rearrangement of initially formed nitrile imines ArCN<sup>+</sup>N<sup>–</sup>R to carbodiimides. The monosubstituted carbodiimide PhNCNH isomerizes to phenylcyanamide, PhNH–CN, and photolysis of the latter causes rapid elimination of HCN and formation of phenylnitrene. When <i>N</i>-methyl groups are present in the tetrazoles, methylnitrene, CH<sub>3</sub>–N, is formed too. In the case of 5-phenyltetrazole, additional hydrogen shift and fragmentation afford cyano- and isocyanonitrenes, NCN and CNN. 2018-08-30 00:00:00 Tetrazole 5- aryltetrazoles carbodiimide formation HCN cm CH arylnitrene Photolysi photolysi 266 nm laser ESR CNN zero-field splitting parameters D nitrile imines ArCN NCN