Synthesis and Spectral, Electrochemical, and Antioxidant Properties of 2-(5-Aryl-6-R-3-phenyl-5,6-dihydro-4H-1,2,4,5-tetrazin-1-yl)-1,3-benzothiazoles

New 2-(5-aryl-6-R-3-phenyl-5,6-dihydro-4H-1,2,4,5-tetrazin-1-yl)-1,3-benzothiazoles were synthesized from the corresponding formazans by alkylation and subsequent cyclization of N-alkyl derivatives. The products were characterized by 1H and 13C NMR, IR, and mass spectra and X-ray diffraction data. Electrochemical properties and antioxidant activity of the synthesized benzothiazole derivatives were studied.