Intramolecular Charge Transfer in (Dialkylamino)nitrobiphenyls

The deep color of the new biaryls reported in the previous Comrnunication['I must be ascribed to a charge transfer (CT) transition. Since within the region 7.5. to 7.5. mole/liter the absorption is independent of concentration, intermolecular origin of this CT interaction can be ruled out. For interpretation of intramolecular charge-transfer processes, knowledge of the molecular geometry is a prerequisite : information about the structure of the biphenyls ( I ) to ( 3 ) may be gained from the 'HNMR spectra.