Role of Sulfonate Appendage in the Protein Binding Affinity of Half-Sandwich Ruthenium(II)(η⁶-p-Cym) Complexes

Mono- and binuclear benzimidazole based half-sandwich organoruthenium(II) compounds; [Ru_n(triazolate^{COOCH3,COOCH3})_n(η⁶-p-Cym)_nL]^0/+/2+ (n = 1, L = L^CH2CH3 (7) and HL^SO3H (8); n = 2, L = L^DTP (9)) were synthesized by [3+2] free catalyzed cycloaddition reaction of azide complexes 4–6 with electron-poor alkyne dimethyl acetylene dicarboxylate. In comparison with the parent [Ru_nCl_n(η⁶-p-Cym)_nL]^0/+/2 complexes (1–3), the lysozyme binding affinity of the corresponding triazolate compounds 7–9 was investigated by electrospray ionization mass spectrometry. Complexes bearing benzimidazole ligand with an alkylated sulfonate side chain (2 and 8) are able to bind lysozyme noncovalently, which have not been clearly seen by other investigated Ru(II) complexes. The complexes were assessed for their potential antimicrobial activity against some representative microbes. Complex 9 exhibits antifungal activity against C. albicans (MIC = 24 nm) and C. neoformans (MIC = 12 nm), perfect blood compatibility as well as no toxicity to non-malignant cell line (human embryonic kidney cells (HEK293).