Purification and Fluorescence Characteristics of Carbazole

Abstract

Crude carbazole (C₁₂H₉N), extracted from coal--tar pitch, contains a small amount of impurities having very similar lattice constants to those of carbazole. In order to remove these im purities, crude carbazole (10 g) was heated with boiling maleic anhydride (20 g) and chloranil (1g) in, 2, 4-trichlorobenzene (30 ml). Next, it was treated with metallic sodium in isopentyl alcohol, subTlhimated, passed through alumina column, and refined by zone melting.
The fluorescence spectra and the wavelength dependence of fluorescence life -time of the evaporated thin film of carbazole were measured in order to detect the impurities. The fluorescen ce maxima of the highly pure carbazole were at 345, 358 and 370 nm at room temperature, and at 345, 351, 370 and 392 nm at liquid nitrogen temperature. The fluorescence maxima of imp u re carabazole were observed not only in the region of 330-400 nm but also in the region s less than 330 nm and more than 400 nm.
On the other hand, the average fluorescence life-time of the evaporated thin film of the ghly pure carbazole was from 18.1 to 21.0 nsec in the region of 345-417 nm at room temperature, and the wavelength dependence was small. The life-time of the impure carba zole was from 7.3 to 22.0 n sec, and the wavelength dependence was large.