Structural Studies, Antimicrobial Activity and Protein Interaction of Photostable Terpyridine Silver(I) Complexes

Photostable mono- and binuclear silver(I) complexes derived from terpyridine ligands (4′-(2-pyridyl)-2,2′:6′,2′′-terpyridine (L^PY) (1), 4′-(4-phenyl morpholine)-2,2′:6′,2′′-terpyridine (L^morph) (2) and 1,4-bis (2,2′:6′,2′′-terpyridin-4′yl) benzene (L^DB) (3)) were synthesized and fully characterized in the solution and solid-state including [¹H–¹⁵N] heteronuclear multiple bond coherence (HMBC) NMR analysis and single-crystal X-ray analysis of five-coordinates [Ag₂(L^PY)₂(CH₃CN)₂](SO₃CF₃)₂. Based on the NMR and ESI-MS data, complex 1 exists as dimeric species, formed by head-to-tail interaction, while monomeric species of 3 predominantly exist in the same solvents. The protein binding affinity of 1–3 was investigated by using hen white egg lysozyme (HEWL). To explore where the metalation site of HEWL is, the interactions between the complexes and histidine were studied by NMR. The morpholine ligand and its Ag(I) complex (2) exhibited interesting antimicrobial activity. In comparison with AgOSO₂CF₃, compounds 1–3 displayed lower cytotoxicity to non-malignant human embryonic kidney (HEK293) cells, and induced negligible haemoglobin release.