title: Synthesis, structure, and physicochemical properties of dinuclear NiII complexes as highly efficient functional models of phosphohydrolases.
abstract: As metal ions are present in the catalytic sites of several enzymes, attention has been focused on the synthesis and characterization of metal complexes able to act as biomimetic functional and structural models for these systems. In this study, a novel dinuclear NiII complex was synthesized, [Ni2(L2)(OAc)2(CH3CN)]BPh4 (2) (HL2=2-[N-(2-(pyridyl-2-yl)ethyl)(1-methylimidazol-2-yl)amin omethyl]-4-methyl-6-[N-(2-(imidazol-4-yl)ethyl)amino methyl]phenol), employing a new unsymmetrical dinucleating ligand containing N,O-donor groups as a model for hydrolases. Complex 2 was characterized by a variety of techniques including: elemental analysis, infrared and UV-vis spectroscopies, molar conductivity, electrochemistry, potentiometric titration, magnetochemistry, and single-crystal X-ray diffractometry. The structural and magnetochemical data of 2 allow us to consider this complex as a structural model for the active site of the ureases, as previously reported for [Ni2(L1)(OAc)2(H2O)]ClO4.H2O (1) (HL1=2-[N-bis-(2-pyridylmethyl)aminomethyl]-4-methyl-6-[N-(2-pyridylmethyl)aminomethyl] phenol). The characterization of complexes 1 and 2 (mainly by X-ray diffraction and potentiometric titration) led us to study their reactivities toward the hydrolysis of the substrate bis(2,4-dinitrophenyl)phosphate (2,4-BDNPP). These studies revealed that complexes 1 and 2 show the best catalytic activity reported so far, with acceleration rates 8.8x10(4) and 9.95x10(5) times faster, respectively, than the uncatalyzed hydrolysis of 2,4-BDNPP. Catalytic activity of 2 on 2,4-DNPP showed that the monoester is hydrolyzed 27 times slower than the 2,4-BDNPP diester under identical experimental conditions. Therefore, 1 and 2 can undoubtedly be considered highly efficient functional models of the phosphohydrolases.
authors.affiliation: Laboratório de Bioinorgânica e Cristalografia (LABINC), Departamento de Química, Universidade Federal de Santa Catarina, 88040-900 Florianópolis, Santa Catarina, Brazil.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Greatti
authors.forename: Marciela
authors.initials: M
authors.lastname: Scarpellini
authors.forename: Rosely A
authors.initials: RA
authors.lastname: Peralta
authors.forename: Annelise
authors.initials: A
authors.lastname: Casellato
authors.forename: Adailton J
authors.initials: AJ
authors.lastname: Bortoluzzi
authors.forename: Fernanado R
authors.initials: FR
authors.lastname: Xavier
authors.forename: Rafael
authors.initials: R
authors.lastname: Jovito
authors.forename: Marcos Aires
authors.initials: MA
authors.lastname: de Brito
authors.forename: Bruno
authors.initials: B
authors.lastname: Szpoganicz
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Tomkowicz
authors.forename: Michal
authors.initials: M
authors.lastname: Rams
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Haase
authors.forename: Ademir
authors.initials: A
authors.lastname: Neves
mesh_terms: D018360:Crystallography, X-Ray; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry*; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry*
chemical_list: D009532:Nickel; D010744:Phosphoric Monoester Hydrolases