Effects of Different Substituents on the Crystal Structures and Antimicrobial Activities of Six Ag(I) Quinoline Compounds

• Published in: Inorganic chemistry Vol. 52; no. 7; pp. 4046 - 4060
• Main Authors: Massoud, Alshima’a A, Langer, Vratislav, Gohar, Yousry M, Abu-Youssef, Morsy A. M, Jänis, Janne, Lindberg, Gabriella, Hansson, Karl, Öhrström, Lars
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 01.04.2013
• Subjects: Anti-Infective Agents - chemical synthesis; Anti-Infective Agents - pharmacology; antibacterial; bacterial-resistance; behavior; Coordination Complexes - chemical synthesis; Coordination Complexes - pharmacology; coordination polymers; Crystallography, X-Ray; Hydrogen Bonding; intermolecular interactions; Ligands; Microbial Sensitivity Tests; Models, Molecular; molecular-crystals; nitrate; Proteus mirabilis - drug effects; Proteus mirabilis - growth & development; Pseudomonas aeruginosa - drug effects; Pseudomonas aeruginosa - growth & development; Quinolines - chemistry; Silver - chemistry; silver(i) complexes; Spectrometry, Mass, Electrospray Ionization; Staphylococcus aureus - drug effects; Staphylococcus aureus - growth & development; Streptococcus pyogenes - drug effects; Streptococcus pyogenes - growth & development; Structure-Activity Relationship; wound dressings
• ISSN: 0020-1669; 1520-510X; 1520-510X
• DOI: 10.1021/ic400081v

The syntheses and single crystal X-ray structures of [Ag(5-nitroquinoline)2]NO3 (1), [Ag(8-nitroquinoline)2]NO3·H2O (2), [Ag(6-methoxy-8-nitroquinoline)(NO3)] n (3), [Ag(3-quinolinecarbonitrile)(NO3)] n (4), [Ag(3-quinolinecarbonitrile)2]NO3 (5), and [Ag(6-quinolinecarboxylic acid)2]NO3 (6) are described. As an alternative to solution chemistry, solid-state grinding could be used to prepare compounds 1 and 3, but the preparation of 4 and 5 in this way failed. The Ag(I) ions in the monomeric compounds 1, 2, 5, and 6 are coordinated to two ligands via the nitrogen atoms of the quinoline rings, thereby forming a distorted linear coordination geometry with Ag–N bond distances of 2.142(2)–2.336(2) Å and N–Ag–N bond angles of 163.62(13)°–172.25(13)°. The 1D coordination polymers 3 and 4 contain Ag(I) centers coordinating one ligand and two bridging nitrate groups, thereby forming a distorted trigonal planar coordination geometry with Ag–N bond distances of 2.2700(14) and 2.224(5) Å, Ag–O bond distances of 2.261(4)–2.536(5) Å, and N–Ag–O bond angles of 115.23(5)°–155.56(5)°. Hirshfeld surface analyses of compounds 1–6 are presented as d norm and curvedness maps. The d norm maps show different interaction sites around the Ag(I) ions, i.e., Ag···Ag interactions and possible O–H···O, C–H···O, C–H···N, and C–H···C hydrogen bonds. Curvedness maps are a good way of visualizing π–π stacking interactions between molecules. The antimicrobial activities of compounds 1, 2, and 6 were screened against 15 different multidrug-resistant strains of bacteria isolated from diabetic foot ulcers and compared to the antimicrobial activities of the clinically used silver sulfadiazine (SS). Compound 2 showed activity similar to SS against this set of test organisms, being active against all strains and having slightly better average silver efficiency than SS (5 vs 6 μg Ag/mL). Against the standard nonresistant bacterial strains of Staphylococcus aureus, Pseudomonas aeruginosa, Proteus mirabilis, and Streptococcus pyogenes, compound 1 performed better than silver nitrate, with an average MIC of 6 μg Ag/mL versus 18 μg Ag/mL for the reference AgNO3. Electrospray ionization mass spectrometry (ESI-MS) analyses of compounds 3 and 6 in DMSO/MeOH confirm the two-coordinated Ag+ complexes in solution, and the results of the 1H NMR titrations of DMSO solutions of 5-nitroquinoline and 8-nitroquinoline with AgNO3 in DMSO suggest that 5-nitroquinoline is more strongly coordinated to the silver ion.