The antimicrobial activity of mononuclear ruthenium(II) complexes containing the dppz ligand

Liu Xuewen; Biyun Sun; Ruby E. M. Kell; Hannah M. Southam; Jonathan A. Butler; Xin Li; Robert K. Poole; Richard Keene; John Grant Collins

Index: 10.1002/cplu.201800042

Full Text: HTML

Abstract

The cis‐α isomer of [Ru(bb7)(dppz)]2+ {dppz = dipyrido[3,2‐a:2′,3′‐c]phenazine; bb7 = bis[4(4'‐methyl‐2,2'‐bipyridyl)]‐1,7‐alkane} has been synthesised. The minimum inhibitory concentrations and the minimum bactericidal concentrations of [Ru(bb7)(dppz)]2+ and its parent complex [Ru(phen)2(dppz)]2+ (phen = 1,10‐phenanthroline) were determined against a range of bacteria. The results showed that both ruthenium complexes exhibited good activity against Gram‐positive bacteria, but [Ru(bb7)(dppz)]2+ showed at least eight‐times better activity across the Gram‐negative bacteria than [Ru(phen)2(dppz)]2+. Luminescence assays demonstrated that [Ru(bb7)(dppz)]2+ accumulated in a Gram‐negative bacterium to the same degree as in a Gram‐positive species, while assays with liposomes showed that [Ru(bb7)(dppz)]2+ interacted more strongly with membranes compared to the parent [Ru(phen)2(dppz)]2+ complex. The DNA binding affinity for [Ru(bb7)(dppz)]2+ was determined to be 6.7 × 106 M‐1. Although more toxic to eukaryotic cells than [Ru(phen)2(dppz)]2+, [Ru(bb7)(dppz)]2+ exhibited greater activity against bacteria than eukaryotic cells.