A highly distorted hexacoordinated silver(I) complex: synthesis, crystal structure, and DFT studies

Ag(I) camphor complexes: antimicrobial activity by design

Eleven new complexes of general formula [Ag(NO₃)(L-Y)₂] corresponding to Ag(I) camphorimine complexes [Ag(NO₃)(OC₁₀H₁₄NY)₂] (Y=NMe₂ (1); OH (2); C₆H₅ (3); 4-MeC₆H₄, (4); 3,5-(CH₃)₂C₆H₃ (5); 3-OHC₆H₄, (6); 3-ClC₆H₄ (7); 4-ClC₆H₄ (8); 4-FC₆H₄ (9); 4-CF₃C₆H₄ (10)) and the camphor sulfonylimine complex [Ag(NO₃)(O₂SNC₁₀H₁₄NY)₂] (Y=NH₂) were synthesized/characterized and their structural properties and antibacterial activity studied to gain insights into the structure-antimicrobial activity relationships. Five of the complexes were selected as representative examples and structures were optimized by Density Functional Theory calculations. The results show that the imine substituents (Y) at the camphor ligands drive the structure of the complexes from distorted octahedral to trigonal prismatic or linear ionic while the effect of the sulfonylimine ring does not appreciably affects the geometry of the complex. The lipophilicity and polarity which are important parameters concerning the biological activity of the complexes are also high dependent of the characteristics of the camphor ligands. The redox properties of the complexes studied by cyclic voltammetry showed that their reduction potentials are essentially independent of their electronic and steric properties. The antibacterial activity of all the complexes, against Gram-positive (S. aureus Newman) and Gram-negative (Escherichia coli ATCC25922, Pseudomonas aeruginosa 477, Burkholderia contaminans IST408) strains was evaluated through calculation of MIC values. Results show that complexes with camphor imine ligands (1-10) that combine high lipophilicity with low dipolar moment (3-5) exhibit enhanced antibacterial activity. The ability to establish hydrogen bonding emerged as an important contribution to the antibacterial activity of the camphor sulphonylimine complex 11 (Y=NH₂).

Synthesis, Crystal Structure and DFT Studies of a New Dinuclear Ag(I)-Malonamide Complex

The synthesis and structural aspects of a new dinuclear silver (I) complex with malonamide type ligand (L) is reported. Each Ag ion in the [Ag₂L₂(NO₃)₂]·H₂O complex is coordinated to two ligands, L, each acting as a bridged ligand via its two pyridine arms; Ag(I) acts as a connector between them. Two types of Ag-ligands close contacts were detected: Ag–N1, Ag–N4 from the two L units, and Ag–O5, Ag—O6 from the two nitrate anions, wherein both the nitrate ions are inside the cage formed by the [Ag₂L₂] unit. The coordination geometry around each Ag(I) is a distorted tetrahedron. The [Ag₂L₂(NO₃)₂] complex units are connected by weak intermolecular C—H…O interactions. The different intermolecular interactions were quantified using Hirshfeld surface analysis. Using two DFT methods (B3LYP and WB97XD), the nature and strength of the Ag–N and Ag–O interactions were described using atoms in molecules (AIM) and natural bond orbital (NBO) analyses. Topological parameters indicated that the strength of the two Ag–N bonds was similar, while that of the two Ag–O interactions were significantly different. Moreover, the Ag–N interactions have a predominant covalent character, while the Ag–O interactions are mainly ionic. The NBO analysis indicated that the most important anti-bonding Ag-orbital in these interactions has an s-orbital character.