1-Picryl-2-phenyl-2-(4-picrylamidophenyl) diazenium betaine and its radical-anion: synthesis and physical properties

The betainic title compound represents a structure with interesting physicochemical properties. These were studied by cyclic voltammetry (CV), electron paramagnetic resonance (EPR) spectroscopy, magnetic and spectral measurements. CV investigations show that the process in acetonitrile corresponds to chemically reversible one-electron reduction leading to the formation of a radical-anion. Chemical reduction of the betaine in dichloromethane with powdered sodium ascorbate in the presence of 15-crown-5 ether yielded a radical-anion (with an EPR spectrum similar to that of 2,2-diphenyl-1-picrylhydrazyl, DPPH). Linnett’s theory explains the similarity of EPR spectra for DPPH and the radical-anion. The title betaine is diamagnetic in solid state. In solution, it shows a weak hypsochromic effect. Graphical abstract