Characterization and properties of the charge transfer complex of carbazole derivatives

The purpose of this work is to characterize the charge transfer complex (CTC) formed between one carbazolic derivative and an organic electron acceptor, and to compare some physicochemical properties. We have used either poly( N-vinylcarbazole) or poly(N-butylcarbazole) or again 3,3'-diethyl-9,9'-dicarbazole (DEC) as a donor, and one of the following as acceptor: tetracyanoethylene (TCNE), 2,4,7-trinitro-9-fluorenone (TNF), 1,4-naphthoquinone (NQ) or 2,3-dicyano-1,4-naphthoquinone (DCNQ). The characterization of the CTC has been made following two methods: optical spectroscopy or differential scanning calorimetry (DSC). In fact, when the optical absorption of the CTC corresponds to a well-defined peak, its characterization by optical spectroscopy leads to the determination of some intrinsic properties such as equilibrium constant, molar extinction coefficient, etc. On the contrary, if the optical absorption is indiscernible of the absorption peaks of acceptor or donor alone, we have shown that use of DSC allows us to characterize the formation of CTC measuring the fusion enthalpy of the CTC. These determinations are only described, in this paper, in the case of the dimer DEC as a donor which possesses a well-defined melting point. The CTC between DEC and each acceptor has been characterized in this way. (C) 1997 Elsevier Science S.A.