Spectroscopic analysis, thermodynamic study and molecular modeling of charge transfer complexation between 2-amino-5,6-dimethyl-1,2,4-triazine with DDQ in acetonitrile

Abstract

2-Amino-5,6-dimethyl-1,2,4-triazine (ADMT) reacts instantaneously with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) in acetonitrile (AN) forming reddish brown charge transfer complex. Absorption spectra of the complex produced multi-charge transfer bands at 460, 560 and 589nm, respectively. The molecular composition of the formed complex was studied by applying continuous variation and spectrophotometric titration methods where 1:1 charge transfer complex (ADMT: DDQ) is produced. Benesi–Hildebrand equation has been applied to calculate the formation constant KCT and molecular extinction coefficient; they reached high values asserting high stability of the formed CT complex. Enthalpy and entropy of CT complex formation (–ΔHo and –ΔSo) have been estimated utilizing Van’t Hoff equation where –ΔHo recorded high value confirming strong bonding between donor and acceptor. Moreover, molecular modeling of the formed complex has been carried out using GAMESS interface computations. These computations included measuring bond lengths, bong angles, distance of close contacts as well as potential energy maps.