A series of fifteen silver (I) quinoline complexes Q1–Q15 have been synthesized and studied for their biological activities. Q1–Q15 were synthesized from the reactions of quinolinyl Schiff base derivatives L1–L5 (obtained by condensing 2-quinolinecarboxaldehyde with various aniline derivatives) with AgNO3, AgClO4 and AgCF3SO3. Q1–Q15 were characterized by various spectroscopic techniques and the structures of [Ag(L1)2]NO3Q1, [Ag(L1)2]ClO4Q6, [Ag(L2)2]ClO4Q7, [Ag(L2)2]CF3SO3Q12 and [Ag(L4)2]CF3SO3Q14 were unequivocally determined by single crystal X-ray diffraction analysis. In vitro antimicrobial tests against Gram-positive and Gram-negative bacteria revealed the influence of structure and anion on the complexes′ moderate to excellent antibacterial activity. In vitro antioxidant activities of the complexes showed their good radical scavenging activity in ferric reducing antioxidant power (FRAP). Complexes with the fluorine substituent or the thiophene or benzothiazole moieties are more potent with IC50 between 0.95 and 2.22 mg/mL than the standard used, ascorbic acid (2.68 mg/mL). The compounds showed a strong binding affinity with calf thymus-DNA via an intercalation mode and protein through a static quenching mechanism. Cytotoxicity activity was examined against three carcinoma cell lines (HELA, MDA-MB231, and SHSY5Y). [Ag(L2)2]ClO4Q7 with a benzothiazole moiety and [Ag(L4)2]ClO4Q9 with a methyl substituent had excellent cytotoxicity against HELA cells.

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Four 2-amino-4-(aryl)-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile (Series I) and three 2-amino-1phenyl-7,7-dimethyl-5-oxo-4-(aryl)-1,4,5,6,7,8-hexahydroquinoline-3-carbonitrile (Series II) derivatives were formed via multicomponent microwave reactions as racemic mixtures. The solid-state IR spectra revealed bands in the region between 3190 and 3414 cm −1 attributed to the amino functional group's asymmetric, symmetric, and bending overtone vibration modes. Furthermore, the IR spectra of some of the compounds in each series were similar and this served as an indication of similar structural features in the solid state. This was confirmed via single-crystal X-ray diffraction. A detailed survey of the related 2-amino-3-carbonitrile derivatives in the Cambridge Structural Database revealed 12 classical intermolecular hydrogen-bonding motifs involving the amino functional group. The vast variation in the hydrogen bonding motifs was found to be caused by the type of group bonded to the 4H-pyran (in Series I) or dihydropyridine (in Series II) moiety. In this work, an unprecedented hydrogen bonding motif comprising a non-classical hydrogen bond acceptor was found in one instance. For both Series I and II, the N−H•••N and N−H•••O hydrogen bonds were investigated using noncovalent interaction (NCI) plots and molecular pairwise energy calculations. The contributions of reciprocal N•••H and O•••H contacts (attributed to N−H•••N and N−H•••O, respectively) toward the Hirshfeld surface range between 9.9 and 15.3% in Series I and between 10.8 and 15.0% in Series II. In addition, the compounds showed moderate to good binding affinity to calf thymus DNA (CT-DNA) with intrinsic binding constants (K b ) between 8.00 × 10 4 and 5.00 × 10 5 M −1 for Series I compounds and between 6.60 × 10 4 and 1.45 × 10 5 M −1 for Series II. A relationship was established between the reciprocal N•••H to O•••H contributions ratio from the Hirshfeld surface analysis and K b . Molecular docking studies of each compound's respective enantiomers into DNA were done using canonical−DNA dodecamer (B-DNA) as a model for CT-DNA. The compounds were found to interact with DNA via a minor groove-binding mode. The S-enantiomer for most of the compounds bound favorably compared to their respective R-enantiomers. The ratio of calculated ΔG for the DNA binding of the Renantiomer to that of the S-enantiomer (ΔG R /ΔG S ) follows the same positive trend as the experimental K b value for each compound in Series I while a negative trend was observed for Series II. Finally, a relationship between the Hirshfeld surface analysis and calculated ΔG values was also established in this work.

Transition metal-based drugs have shown to be good therapeutic agents and in the same effort, our work has sort to continue the search for even better ones. Five Schiff bases...