title: Synthesis, characterisation and antibacterial activity of [(p-cym)RuX(L)](+/2+) (X = Cl, H2O; L = bpmo, bpms) complexes.
abstract: Mononuclear half-sandwiched complexes [(p-cym)RuCl(bpmo)](ClO4) {[1](ClO4)} and [(p-cym)RuCl(bpms)](PF6) {[2](PF6)} have been prepared by reacting heteroscorpionate ligands bpmo = 2-methoxyphenyl-bis(3,5-dimethylpyrazol-1-yl)methane and bpms = 2-methylthiophenyl-bis(3,5-dimethylpyrazol-1-yl)methane, respectively, with a dimeric precursor complex [(p-cym)RuCl(μ-Cl)]2 (p-cym = 1-isopropyl-4-methylbenzene) in methanol. The corresponding aqua derivatives [(p-cym)Ru(H2O)(bpmo)](ClO4)2 {[3](ClO4)2} and [(p-cym)Ru(H2O)(bpms)](PF6)2 {[4](PF6)2} are obtained from {[1](ClO4)} and {[2](PF6)}, respectively, via Cl(-)/H2O exchange process in the presence of appropriate equivalents of AgClO4/AgNO3 + KPF6 in a methanol-water mixture. The molecular structures of the complexes {[1]Cl, [3](ClO4)2 and [4](PF6)(NO3)} are authenticated by their single crystal X-ray structures. The complexes show the expected piano-stool geometry with p-cym in the η(6) binding mode. The aqua complexes [3](ClO4)2 and [4](PF6)2 show significantly good antibacterial activity towards E. coli (gram negative) and B. subtilis (gram positive) strains, while chloro derivatives ({[1](ClO4)} and {[2](PF6)} are found to be virtually inactive. The order of antibacterial activity of the complexes according to their MIC values is [1](ClO4) (both 1000 μg mL(-1)) < [2](PF6) (580 μg mL(-1) and 750 μg mL(-1)) < [3](ClO4)2 (both 100 μg mL(-1)) < [4](PF6)2 (30 μg mL(-1) and 60 μg mL(-1)) for E. coli and B. subtilis strains, respectively. Further, the aqua complexes [3](ClO4)2 and [4](PF6)2 show clear zones of inhibition against kanamycin, ampicillin and chloramphenicol resistant E. coli strains. The detailed mechanistic aspects of the aforesaid active aqua complexes [3](ClO4)2 and [4](PF6)2 have been explored, and it reveals that both the complexes inhibit the number of nucleoids per cell in vivo and bind to DNA in vitro. The results indeed demonstrate that both [3](ClO4)2 and [4](PF6)2 facilitate the inhibition of bacterial growth by binding to DNA.
authors: School of Basic Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar, Odisha-751007, India. srikanta@iitbbs.ac.in.
authors: Suman Kumar
authors: SK
authors: Tripathy
authors: Ashoka Chary
authors: AC
authors: Taviti
authors: Niranjan
authors: N
authors: Dehury
authors: Anupam
authors: A
authors: Sahoo
authors: Satyanaryan
authors: S
authors: Pal
authors: Tushar Kant
authors: TK
authors: Beuria
authors: Srikanta
authors: S
authors: Patra
mesh_terms: D000900:Anti-Bacterial Agents / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D001412:Bacillus subtilis / Q000187:drug effects; D060326:Chemistry Techniques, Synthetic; D004247:DNA / Q000378:metabolism; D004563:Electrochemistry; D004926:Escherichia coli / Q000187:drug effects; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D011720:Pyrazoles / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D009942:Organometallic Compounds; D011720:Pyrazoles; C031280:pyrazole; D012428:Ruthenium; D004247:DNA