NOVEL FORMATION OF DIPYRROLO- AND DIINDOLO[1,2-a:2 ',1 '-c]QUINOXALINE DERIVATIVES AND THEIR OPTICAL PROPERTIES

Dipyrrolo- and diindolo[1,2-a:2',1'-c]quinoxaline structures (A and B, respectively) were synthesized from 1,2-di(1-pyrrolyl)- and 1,2-di(1-indolyl)benzene derivatives with iodine using a novel intramolecular coupling reaction. Apparent differences between A and B were observed from UV-VIS absorption and fluorescence spectra. Sharp peaks with a fine structure were observed in the absorption and fluorescence spectra of diindolo[1,2-a:2',1'-c]quinoxaline (2b). Introduction of a phenyl ring at the 6 and 6' positions of the indole moieties of 2b is efficient for imparting a red shift. In addition, the electron-withdrawing group at those positions particularly affected the emission peaks.