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Type: Artigo de periódico
Title: Solid state and solution characterization of a new dinuclear nickel (II) complex: The search for synthetic models for urease
Author: Horn, A
Firn, L
Bortoluzzi, AJ
Szpoganicz, B
Silva, MD
Novak, MA
Neto, MB
Eberlin, LS
Catharino, RR
Eberlin, MN
Fernandes, C
Abstract: The X-ray molecular structure and, magnetic, and spectroscopic properties, as well as the analysis of the structural behavior in solution of a novel nickel (II) complex [Ni-2(HBPClNOL)(2)(OAc)ClO4) 1 are reported. Complex 1 was prepared by the reaction between the ligand H2BPCINOL (N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)[(3-chloro)(2-hydroxy)]propylamine), [Ni(H2O)(6)](ClO4)(2) and sodium acetate. Magnetic measurements indicate the presence of a weak antiferromagnefic coupling between the Ni(II) ions in 1, resulting in J = -4.23 cm(-1). Mass spectrometric characterization of the complex 1 was also performed via ESI-MS and ESI-MS/MS experiments and reveals that there are at least three different cations in solution, one mononuclear [Ni(H2BPClNOL)(OAc)](+) and two dinuclear [Ni-2(HBPClNOL)(2)(OAc)](+) and [Ni-2(HBPClNOL)(2)(ClO4)](+) cations, as well as likely a fourth one [Ni(HBPCINOL)](+). Potentiometric titration experiments confirm that under acid conditions, the dinuclear unit is broken. However, under neutral/basic pH values the dinuclear unit is stable and shows the presence of two water molecules coordinated to the nickel ions, resulting in the cation [Ni-2(HBPClNOL)(2)(H2O)(2)](2+). This cation shows two protonation/deprotonation equilibriums with pK(a) values of 9.68 and at 10.29, which are related to the aquo/hydroxo equilibrium associated with the water molecules coordinated to the metal ions. (c) 2006 Elsevier B.V. All rights reserved.
Subject: urease
dinuclear nickel (II) complex
potentiometric studies
Country: Holanda
Editor: Elsevier Science Bv
Citation: Journal Of Molecular Structure. Elsevier Science Bv, v. 797, n. 41699, n. 154, n. 164, 2006.
Rights: fechado
Identifier DOI: 10.1016/j.molstruc.2006.03.043
Date Issue: 2006
Appears in Collections:Unicamp - Artigos e Outros Documentos

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