title: A unique nickel system having versatile catalytic activity of biological significance.
abstract: A new dinuclear nickel(II) complex, [Ni(2)(LH(2))(H(2)O)(2)(OH)(NO(3))](NO(3))(3) (1), of an "end-off" compartmental ligand 2,6-bis(N-ethylpiperazine-iminomethyl)-4-methyl-phenolato, has been synthesized and structurally characterized. The X-ray single crystal structure analysis shows that the piperazine moieties assume the expected chair conformation and are protonated. The complex 1 exhibits versatile catalytic activities of biological significance, viz. catecholase, phosphatase, and DNA cleavage activities, etc. The catecholase activity of the complex observed is very dependent on the nature of the solvent. In acetonitrile medium, the complex is inactive to exhibit catecholase activity. On the other hand, in methanol, it catalyzes not only the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) but also tetrachlorocatechol (TCC), a catechol which is very difficult to oxidize, under aerobic conditions. UV-vis spectroscopic investigation shows that TCC oxidation proceeds through the formation of an intermediate. The intermediate has been characterized by an electron spray ionizaton-mass spectrometry study, which suggests a bidentate rather than a monodentate mode of TCC coordination in that intermediate, and this proposition have been verified by density functional theory calculation. The complex also exhibits phosphatase (with substrate p-nitrophenylphosphate) and DNA cleavage activities. The DNA cleavage activity exhibited by complex 1 most probably proceeds through a hydroxyl radical pathway. The bioactivity study suggests the possible applications of complex 1 as a site specific recognition of DNA and/or as an anticancer agent.
authors.affiliation: Department of Chemistry, University of Calcutta, 92, A. P. C. Road, Kolkata-700 009, India.
authors.forename: Tanmay
authors.initials: T
authors.lastname: Chattopadhyay
authors.forename: Madhuparna
authors.initials: M
authors.lastname: Mukherjee
authors.forename: Arindam
authors.initials: A
authors.lastname: Mondal
authors.forename: Pali
authors.initials: P
authors.lastname: Maiti
authors.forename: Arpita
authors.initials: A
authors.lastname: Banerjee
authors.forename: Kazi Sabnam
authors.initials: KS
authors.lastname: Banu
authors.forename: Santanu
authors.initials: S
authors.lastname: Bhattacharya
authors.forename: Bappaditya
authors.initials: B
authors.lastname: Roy
authors.forename: D J
authors.initials: DJ
authors.lastname: Chattopadhyay
authors.forename: Tapan Kumar
authors.initials: TK
authors.lastname: Mondal
authors.forename: Munirathinam
authors.initials: M
authors.lastname: Nethaji
authors.forename: Ennio
authors.initials: E
authors.lastname: Zangrando
authors.forename: Debasis
authors.initials: D
authors.lastname: Das
mesh_terms: D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry; D008958:Models, Molecular; D009532:Nickel / Q000737:chemistry*; D010084:Oxidation-Reduction; D010879:Piperazines / Q000737:chemistry*
chemical_list: D010879:Piperazines; D009532:Nickel; D004247:DNA