Luminescence of 5-phenyltetrazole and its Derivatives. Part I. Absorption and Fluorescence Spectra

Absorption and fluorence spectra of a series of 5-phenyltetrazole derivatives have been measured. Compounds carrying electron-accepting CN or CÖOH groups in the phenyl ring exhibit dual fluorescence. Investigations carried out in acid and basic media and a comparison of the fluorescence of p-cyano-5-phenyltetrazole and l-methyl-5-(4'-cyano) phenyltetrazole show the anions of respective 5-phenyl-tetrazole derivatives to be responsible for the long-wave fluorescence (Amax ̂ 400 nm). The long-wave fluorescence of some 5-phenyltetrazole derivatives is associated with a considerable charge derealization between the tetrazole and phenyl rings, this being accompanied by mutual twisting of the rings in the excited state. This finding has been confirmed by the absence of the long-wave fluorescence in rigid media.