Photolysis of aromatic azides. Part 2.—Formation and spectra of dinitrenes

Abstract

A group of eight symmetrical p-diazides was investigated. Irradiation at 77°K in a rigid matrix converted the diazides into dinitrenes in two consecutive steps, the azidonitrene being the intermediate. Prolonged irradiation of the dinitrenes with light of wavelength shorter than 300 mµ produced coloured products, tentatively identified as dinitrene positive ions. The conjugated dinitrenes have spectra characteristic of closed aromatic shells, two of the odd electrons on the nitrogens have paired. Pairing is not affected by chain length or by hetero-atoms in the conjugated chain. A break in the conjugation of di-(4-nitrenophenyl)methane prevents electron pairing; the molecule has a characteristic open shell spectrum.