Solvatochromism of Heteroaromatic Compounds: IX. Anions of 3-Nitro-1,2,4-triazol-5-ones

Solvatochromism of the long-wave band in the electronic absorption spectra of 3-nitro-1,2,4-triazol-5-one anions was studied and quantitatively described with the Kamlet-Taft solvent parameters. Azole anions are specifically solvated in amphiprotic solvents. The strength of the hydrogen bond in H complexes with amphiprotic solvents decreases in going to the Franck-Condon excited state. The UV and IR specrta show that 3-nitro-1,2,4-triazol-5-one anions, in contrast to nitroazole anions, are specifically solvated with participation of the carbonyl group. In highly polar organic solvents the 3-nitro-1,2,4-triazol-5-one anion mainly exists in the form of the 1H tautomer.