Effects of methyl substituent on the charge-transfer complexations of dicarbazolylalkanes with p-chloranil, tetracyanoethylene and tetracyanoquinodimethane

Series of 1,n-dicarbazolylalkanes and 1,n-di(3-methylcarbazolyl)alkanes (where n=1-5) were synthesized and the molar extinction coefficients, equilibrium constants, enthalpies, and entropies of their charge-transfer (CT) complexes with the π-acceptors p-chloranil, tetracyanoethylene, and tetracyanoquinodimethane were investigated. 1,n-Di(3-methylcarbazolyl)alkanes formed CT complexes with higher equilibrium constants, more negative enthalpies and entropies than 1,n-dicarbazolylalkanes. Vibrational spectra of CT complexes of one of the donor molecules (1,4-dicarbazolylbutane) with all three acceptors were compared.