MCD studies of biphenyls

The magnetic circular dichroism (MCD) spectra of biphenyl derivatives with electron donating substituents at the C₄ and/or C₄′ positions of biphenyl were measured at room temperature in the wavelength regions of 200 to 350 nm. The biphenyls studied exhibited Faraday B terms caused by a magnetic coupling of the non-degenerate electronic states. A careful inspection of the MCD spectra has enabled us to find hidden bands which were buried in the intense, so-called “conjugation band” of biphenyl, resulting in the preferable assignments of the bands.