Synthesis, crystal structure, antimicrobial activity and DNA-binding of hydrogen-bonded proton-transfer complex of 2,6-diaminopyridine with picric acid

A proton-transfer (charge transfer) complex formed on the reaction between 2,6-diaminopyridine (donor) and picric acid (acceptor) was synthesized and characterized by FTIR, 1H NMR, thermal and elemental analysis. The crystal structure determined by single-crystal X-ray diffraction indicates that cation and anion are joined together by strong N+–H- -O− type hydrogen bonds. The hydrogen-bonded charge transfer (HBCT) complex was screened for its pharmacology such as antimicrobial activity against various fungal and bacterial strains and Calf thymus DNA-binding. The results showed that HBCT complex (100 μg/ml) exhibited good antibacterial antifungal activity as that of standard antibiotics Tetracycline and Nystatin. A molecular frame work through H-bonding interactions between neighboring moieties is found to be responsible for high melting point of resulting complex. This has been attributed to the formation of 1:1 HBCT complex.