Syntheses, structural characterization, and basic properties of unsymmetrically substituted biphenoquinones

Unsymmetrically substituted biphenoquinones, 3,5-dimethyl-3′,5′-diphenylbiphenoquinone and 3,5-di-tert-butyl-3′,5′-diphenylbiphenoquinone, were prepared by a mixed oxidative coupling reaction of the corresponding phenols with potassium permanganate in CHCl3. The properties of the quinones such as reduction potential and visible light absorption were measured and positively shifted reduction potentials and bathochromic shifts as a result of light absorption were found to be characteristic of the π-expanded quinones. We also carried out single-crystal diffraction study and uncovered a unique packing motif attributable to their unsymmetrical structures.