Spectroscopic study of the complexation of 5,6,14,15-dibenzo-1,4-dioxa-8,12-diazacyclopentadeca-5,14-diene with some polynitrophenol derivatives in chloroform solution

The complex formation between 5,6,14,15-dibenzo-1,4-dioxa-8, 12-diazacyclop entadeca-5,14-diene (DBDA15C4) and 4-nitrophenol (MNP), 2,4-dinitrophenol ( DNP) and 2,4,6-trinitrophenol (TNP) have been studied spectrophotometricall y in chloroform solution. The resulting proton transfer-charge transfer com plexes are formulated as DBDA15C4.TNP and DBDA15C4.(TNP)(2), confirming cha racterizations by microchemical analysis and IR spectroscopy. The equilibri um constants for the resulting complexes (K-1 and K-2) were evaluated from the nonlinear least-squares fitting of the absorbance-mole ratio data. The overall stability of the resulting complexes was found to vary in the order TNP > DNP > MNP. The enthalpies and entropies of the successive complexati on reactions for the DBDA15C4-TNP system were determined from the temperatu re dependence of the equilibrium constants.