Structural and Antibacterial Properties of Silver(I) Compounds with N-donor Ligands: A Challenge for Medical Applications
Doctoral thesis, 2011
In this thesis, new silver(I) nitrate compounds with N-donor heterocyclic ligands are described. The structures of the obtained crystalline compounds 1-19 were analysed using X-ray single-crystal diffraction. Compounds 1-14 and19 have monomeric structures, while compounds 16, 17, and 18 have 1D chain structures with distorted linear and trigonal planar coordination geometries, respectively, around the silver(I) ions. Compound 15 has a (6,3)-2D honeycomb structure with distorted tetrahedral geometries around the silver(I) ions. The intermolecular interactions of compounds 1-19 (hydrogen bonding and π...π stacking profiles) are discussed in comparison to each other and to certain structures from the literature. The Hirshfeld surfaces of chemically related compounds were also elucidated.
In vitro antibacterial testing of some of these compounds was performed using Multi-Drug Resistant Strains (MDRS) isolated from diabetic foot ulcers and standard strains. Most of the compounds showed higher antibacterial activities than those of silver(I) sulphadizine (which is used for topical treatment of burns) and some selected antibiotics. Compound 14 [Ag(dafon)2NO3]also showed a strong binding ability to ctDNA. Furthermore, hydrogels loaded with 14 appear to be promising for applications in burn treatment and wound dressing.
Since the antibacterial activities of these compounds were tested (in vitro) in solution and their proposed applications will be in solution (in vivo), some solution studies were performed with Electrospray Ionisation Mass Spectrometry (ESI-MS), 1H-NMR, and UV-vis titrations. The structures in solution of the tested compounds were consistent with the structures defined by X-ray analyses of the solid state, with the exception of compounds 15 [Ag2(bpym)(NO3)(sub>2]nand 16 [Ag(mnqu)(NO3)]n. A new synthetic method and solution chemistry for the previously determined structures [Ag3(2-aminopyridine)4(NO3)2]NO3, 20 and [Ag(2-aminopyridine)3]NO3, 21 are also presented.