Synthesis,characterization and electrochemical behaviour of some substituted 2-phenyl-4-(4'-arylazophenyl)-3-thioxo-2H-3,4-dihydro-2,4,9,10-tetra-azaphenanthren-1-ones

摘要

A new facile method for the synthesis of 2-phenyl-4-(4'-arylazphenyl)-3-thioxo-2H-3,4-dihydro-2,4,9,10-tetra-azaphenanthren-1-ones has been developed.Structures of all the synthesized compounds have been established on the basis of their consistent elemental,IR and NMR spectral data.The electrochemical reductions of synthesized compounds have been studied over a wide pH range in B.R.buffers at dropping-mercury and glassy carbon electrodes.All the compounds are found to undergo cathodic reduction by the uptake of two-electrons in diffusion-controlled and irreversible manner.On the basis of polarography,cyclic voltammetry and coulometry,a plausible reduction mechanism is suggested to account for the reduction of azo site in the compounds.Kinetic parameters i.e.,charge-transfer coefficient (alpha_n),forward rate constant (K~o_(f,h)),diffusion-coefficient (D_0~(1/2)),and diffusion current constant (I) have also been calculated.An interesting correlation between half-wave potential (E_(1/2)) values of various substituents and Hammett substituents constant (a) have also been interpreted.