Abstract
Electron donor-acceptor complexes (CT-complexes) formed between hexane-1,6-diol (hexol) as a donor with quinol (Q(OH) 2), picric acid (PA), 1,3-dinitrobenzene (DNB), chloranilic acid (CLA) and p-chloranil (CHL) as a. -acceptors have been synthesized and spectroscopically studied in methanol as a solvent at room temperature. Based on the elemental analyses and photometric titrations, the stoichiometry of CT complexes formed with Q(OH) 2, PA, CLA and CHL as acceptors are found to be 1: 2 ratio, but with DNB acceptor is found to be 1: 1 ratio. Benesi-Hildebrand and its modification methods were applied to estimate the spectroscopic and physical data. The spectroscopic techniques such as (IR, 1H-NMR, and UV-vis) spectra and elemental analyses (C, H, N) as well as thermogravimetric analysis (TG) were used to characterize the chelating behavior of the five hexol synthetic CT complexes. The kinetic thermodynamic parameters such as, activation energy, E*, enthalpy,. H*, entropy,. S*, and Gibbs free energy,. G*, have been calculated from TG curves, using Coats-Redfern and Horowitz-Metzger methods. The hexol CT-complexes were antimicrobial assessed against two kinds of bacteria and fungi species. The results show that, hexol complexes which have high energy gap values (HOMO-LUMO) exhibit good antibacterial activity against all bacteria species under investigation, and only hexol/ Q(OH) 2 and hexol/ PA complexes which possess highest energy gap value exhibit a good antifungal activity against Candida albicans. These results reveal that the energy gap reflects the chemical and biological activity of the charge transfer complex.