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Unprecedented dinuclear Robson type macrocyclic complexes having two +iii metal ions in two compartments and the role of the diimino moiety on the stability of metal ion oxidation states
Published in Royal Society of Chemistry
Volume: 43
Issue: 42
Pages: 15737 - 15751
The work in this investigation deals with the syntheses, characterization, crystal structures and catechol oxidase activity of four diphenoxo-bridged CoIIICoIII compounds of composition [CoIIICoIIILMe-pn(N3)4]·6H2O (1), [CoIIICoIIILMe-pn(N3)4]·4H2O (2), [CoIIICoIIILEt-pn(N3)4]·3.5H2O (3) and [CoIIICoIIILEt-pn(N3)4]·CH3CN·2.5H2O (4), and two diphenoxo-bridged CoIIICoII compounds of composition [CoIIICoIILMe-Me2pn(N3)3]·2H2O (5) and [CoIIICoIILEt-Me2pn(N3)3]·H2O (6). In these compounds, H2LMe-pn, H2LEt-pn, H2LMe-Me2pn and H2LEt-Me2pn are four Robson type tetraiminodiphenolate macrocyclic ligands, in which the superscript Me and Et indicate that the dialdehyde components are 4-methyl-2,6-diformyl-phenol and 4-ethyl-2,6-diformyl-phenol, respectively, while pn and Me2pn indicate that the diamine components are 1,3-diaminopropane and 2,2-dimethyl-1,3-diaminopropane, respectively. The CoIIICoIII compounds 1-4 are further characterized by 1H NMR spectra. Compounds 1 and 3 are prepared following a metal-templated synthesis, while compounds 2 and 4 are prepared by direct synthesis, which includes using a pre-isolated macrocycle, [H4LMe-pn](ClO4)2/[H4LEt-pn](ClO4)2, as a reactant. On changing the diamine component of the corresponding macrocycle from 1,3-diaminopropane to 2,2-dimethyl-1,3-diaminopropane, but otherwise following the similar reaction procedure (both direct and template), the CoIIICoII compounds [CoIIICoIILMe-Me2pn(N3)3]·2H2O (5), [CoIIICoIILEt-Me2pn(N3)3]·H2O (6), [CoIIICoIILMe-Me2pn(N3)3]·0.5MeCN·0.27H2O (5A; Inorg. Chim. Acta, 2014, 412, 38) and [CoIIICoIILEt-Me2pn(N3)3]·MeCN (6A; Dalton Trans., 2013, 42, 4561) are formed, rather than CoIIICoIII compounds. Like compounds 5A and 6A, all the compounds 1-6 show catechol oxidase activity (substrate: 3,5-di-tert-butyl catechol). The kinetic parameters for 1, 3 and 6 have been determined. Their Kcat values are, respectively, 212.6, 188.0 and 191.3 h-1. ESI-MS (positive) spectra of some representative cases (with and without the substrate) have been recorded and the positive species have been assigned well. Unprecedented and surprising aspects of the composition/structure and properties of the complexes in this investigation have been discussed. This journal is © the Partner Organisations 2014.
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JournalData powered by TypesetDalton Transactions
PublisherData powered by TypesetRoyal Society of Chemistry
Open AccessNo