Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/60152
Type: Artigo de periódico
Title: Infinite zig-zag and cyclic-tetranuclear isomeric imidazolate-bridged polynuclear copper(II) complexes: Magnetic properties, catalytic activity and electrospray mass and tandem mass spectrometry characterization
Author: Alves, WA
Cerchiaro, G
Paduan, A
Tomazela, DM
Eberlin, MN
Ferreira, AMD
Abstract: Two mononuclear copper(II) complexes 1 and 2 with the unsymmetrical tridentate ligands 2- and 4-[((imidazol-2-ylmethylidene)amino)ethyl]pyridine have been prepared. In alkaline solution, deprotonation of the imidazole moiety. in 1 and 2 promotes self-assembly, which yielded two structurally different species. Depending on the binding site in the imidazole ring, a polymeric complex with an infinite zig-zag-chain 3, or a cyclic-tetranuclear complex 4 is formed, as shown by spectroscopic and spectrometric analysis. Herein, structural characterization of these isomeric polynuclear complexes was performed by electrospray mass (ESI-MS) and tandem mass spectrometric experiments (ESI-MS/MS). Each isomer was shown to be stable in methanolic solutions and to display unique mass spectra with characteristic multiply charged molecular and fragment ions, corroborating previous data by EPR measurements. Magnetic data in the solid state fit a typical curve for an one-dimensional infinite regular chain system, with J= -(32.4 +/- 1.2) cm(-1) and g = 2.03 for 3, and that of a cyclic-tetranuclear structure with J = -(55.5 +/- 0.4) cm(-1) and g = 2.29 for 4. In the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) by molecular oxygen, both complexes were shown to act as efficient catalysts, exhibiting very similar ratios: k(cat)/K-M = 9.12 x 10(6) mol(-1) dm(3) min(-1) for 3 and 8.73 x 10(6) mol(-1) dm(3) min(-1) for 4. These similar ratios indicate that interactions between the metal centres in 3 or 4 and the substrate in solution occur predominantly at the outside of the catalyst framework. (c) 2005 Elsevier B.V. All rights reserved.
Subject: copper(II) complexes
ESI mass spectrometry
magnetic properties
catalytic activity
Country: Suíça
Editor: Elsevier Science Sa
Rights: fechado
Identifier DOI: 10.1016/j.ica.2005.06.006
Date Issue: 2005
Appears in Collections:Unicamp - Artigos e Outros Documentos

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