Ag(I)‐mediated hydrolysis of hydrazone to azine: Synthesis, X‐ray structure, and biological investigations of two new Ag(I)‐azine complexes

Abstract Reactions of 2‐(1‐hydrazonoethyl)pyridine with silver salts AgX (X = NO 3 ¯ or ClO 4 ¯) proceeded via the hydrolysis of the pyridine ligand and the formation of the dinuclear [AgL 1 ] 2 (ClO 4 ) 2 ( 1 ) and [AgL 1 (NO 3 )] 2 ( 2 ) complexes of the azine ligand, 1,2‐ bis (1‐(pyridin‐2‐yl)ethylidene)hydrazine ( L 1 ). The structures of the obtained complexes were determined by single crystal X‐ray diffraction. The azine ligand ( L 1 ) is acting as a bidentate ligand and connects the two Ag‐sites via the pyridine and the azine nitrogen atoms. In complex 1 , the Ag(I) ion is tetra‐coordinated, while in complex 2 the Ag(I) ion is penta‐coordinated due to the presence of additional interaction with one of the oxygen atoms of the nitrate ion. As a result, the azine ligand is significantly twisted in complex 2 compared to complex 1 . The optimized geometries of three conformers of L 1 were calculated using DFT calculations, and their kinetic and thermodynamic stability were analyzed. It was found that a free rotation of L 1 is required prior to the chelation of the Ag(I) ion. The packing in complex 1 is controlled by H…H, O…H, and Ag…O interactions, but in complex 2 , the O…H and N…H interactions are the most significant. Complex 2 has better antifungal activity against Aspergillus fumigatus and Candida albicans than the antifungal drug Ketoconazole. Also, the nitrato complex 2 has a promising antioxidant activity compared to the perchlorate complex 1 . The cytotoxicity against colon carcinoma HCT‐116 cell line is higher for complex 1 (IC 50 = 19.72 ± 0.94 μg/ml) than complex 2 (IC 50 = 68.31 ± 2.97 μg/ml).