Novel 3,6-unsymmetrically disubstituted-1,2,4,5-tetrazines: S-induced one-pot synthesis, properties and theoretical study

Abstract

18 unprecedented tetrazines unsymmetrically substituted at C3 and C6 by an aromatic heterocycle have been successfully prepared by the S-induced reaction of aromatic nitriles with hydrazine hydrate under thermal conditions. The spectral property investigation suggests that compounds 4d, 4e, 4f, 4p, 4q, 4r, and 4v can display intense fluorescence in the visible region, and their fluorescent properties are affected by the substituents both in tetrazine and in phenyl rings. Moreover, the electrochemical behaviors of these synthesized tetrazines are demonstrated to be fully reversible. Furthermore, density functional theory (DFT) calculations for these compounds were performed to investigate their optimized structures, Fukui function and reactivity or selectivity in the inverse electron demand Diels–Alder reaction.