Synthesis, spectrophotometric, structural and thermal studies of the charge transfer complex of p-phenylenediamine, as an electron donor with pi acceptor 3,5-dinitrobenzoic acid.

The interaction between p-phenylenediamine (PPD) as a donor with the pi acceptor 3,5-dinitrobenzoic acid (DNB) has been investigated spectrophotometrically in methanol at room temperature. CT complex formed as a result of transfer of lone pair of electrons and exhibits well resolved charge transfer bands in the regions where neither donor nor acceptor have any absorption. The stoichiometry of the charge transfer complex (CTC) was found to be 1:1. The solid state CTC has also been synthesized, and has been characterized by elemental analysis, FTIR spectra, (1)H NMR spectroscopy and electronic absorption. The thermal stability of CT complex was studies using TGA and DTA analyses techniques. On the basis of the studies, the structure of CT complex is [(PPD)(DNB)], and a general mechanism for its formation is proposed. The formation constant and other physical parameters of the CT complex were determined by the Benesi-Hildebrand equation.