Preparation, spectroscopic and antibacterial studies on charge-transfer complexes of 2-hydroxypyridine with picric acid and 7,7′,8,8′-tetracyano-p-quinodimethane

• Spectroscopic investigations on the interaction of 2-hydroxypyridine as an electron donor with electron acceptors.
• Electron acceptors used in this study are picric acid (HPA) and 7,7′,8,8′-tetracyano-p-quinodimethane (TCNQ).
• The prepared CT-complexes have the general formulas [(H2PyO)(PA)] and [(HPyO)(TCNQ)].
• The CT-complexes are characterized through elemental and thermal analyses, UV–Vis, IR, 1H NMR spectroscopies.
• The values of KC, ECT, f, μ, Ip, ΔG°, and antimicrobial data of CT-complexes are presented.

The reactions of electron acceptors such as picric acid (HPA) and 7,7′,8,8′-tetracyano-p-quinodimethane (TCNQ) with 2-hydroxypyridine (HPyO) have been investigated in EtOH at room temperature. Based on elemental analysis and IR spectra of the solid CT-complexes along with the photometric titration curves for the reactions, the data obtained indicate the formation of 1:1 charge transfer complexes [(H2PyO)(PA)] and [(PyO)(HTCNQ)], respectively. The infrared and 1H NMR spectroscopic data indicate a charge transfer interaction associated with a proton migration from the acceptor to the donor followed by intramolecular hydrogen bonding in [(H2PyO)(PA)] complex. Another charge transfer interaction was observed in [(PyO)(HTCNQ)] complex. The formation constants (KCT) for the CT-complexes are shown to be strongly dependent on the type and structure of the electron acceptors. Factors affecting the CT-processes and the kinetics of thermal decomposition of the complexes have been studied. The CT complexes were screened for their antibacterial activities against selected bacterial strains.

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