Synthesis of 4′-substituted-2,2′;6′,2"-terpyridine Ru(II) complexes electrochemical, fluorescence quenching and antibacterial studies

Three new Ru(II) terpyridine complexes viz. [Ru(BBtpy)(2)](PF6)(2) [Ru(L1)] (BBtpy = 4'-(4benzyloxybenzaldehyde)-2,2':6',2 ''-terpyridine), [Ru(BMBtpy)(2)](PF6)(2) [Ru(L2)] (BMBtpy = 4'-(4benzyloxy-3-methoxybenzaldehyde)-2,2':6',2"-terpyridine) and [Ru(BEBtpY)(2)](PF6)(2) [Ru(L3)] (BEBtpy = 4'-(4-benzyloxy-3-ethoxybenzaldehyde)-2,2':6',2 ''-terpyridine) have been synthesized and characterized. The MALDI-TOF/MS fragmentation pattern of [Ru(BMBtpy)2](PF6)2 complex exhibits a molecular ion peak at m/z = 987.09 [M-2PF(6)](2+) fragment. These Ru(II) complexes are redox active, show both metal centered oxidation and ligand centered reduction processes. The peak potential and peak current I-pa and I-PC also undergo definite shift and increase with increase in the scan rate (20-120 mV/s). The fluorescence of Ru(II) complexes [Ru(L1)], [Ru(L2)] and [Ru(L3)] are effectively quenched by 1,4benzoquinone and 1,4-naphthoquinone in acetonitrile. The antibacterial activity of ruthenium(II) complexes were screened against four human pathogens both gram -positive bacteria (Bacillus subtilis, Staphylococcus aureus) and gram negative bacteria (Escherichia coli, Klebsiella pneumonia) by the well diffusion method. The antibacterial activity of Ru(II) complexes is comparable to that of standard antibiotics like tetracycline. (C) 2016 Elsevier B.V. All rights reserved.