Synthesis and Optical Properties of 1,3-Bis(Arylimino) isoindoline-4,7-diols

A novel, simple and efficient CuBr2-catalyzed reaction of 3,6-dihydroxyphthalonitrile with arylamines to produce 1,3-bis(arylimino)isoindolines has been developed. Under the optimal conditions, thirteen 1,3-bis-(arylimino) isoindoline derivatives and one 2,3-bis(1H-benzo [d]- imidazole-2-yl)benzene-1,4-diol were obtained in yields among 51-93%. A reasonable mech-anism involving promotion of CuBr2 to 3,6-dihydroxyphthalonitrile is proposed based on experimental results. The optical properties of some products were determined, which resulted in a potential proton transferring dye, 3e (1,3-bis(2-methoxyphenylimino)-isoindoline-4,7-diol), and a pH fluorescent probe in pH range of 7.00-9.30, 3f (1,3-bis(4-hydroxyphenylimino)-isoindoline-4,7-diol).