A [2 × 2] nickel(II) grid and a copper(II) square result from differing binding modes of a pyrazine-based diamide ligand

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dc.contributor.author Klingele, J en
dc.contributor.author Boas, JF en
dc.contributor.author Pilbrow, JR en
dc.contributor.author Moubaraki, B en
dc.contributor.author Murray, KS en
dc.contributor.author Berry, KJ en
dc.contributor.author Hunter, KA en
dc.contributor.author Jameson, GB en
dc.contributor.author Boyd, Peter en
dc.contributor.author Brooker, S en
dc.date.accessioned 2011-09-06T02:14:49Z en
dc.date.issued 2007 en
dc.identifier.citation DALTON T 633-645 2007 en
dc.identifier.issn 1477-9226 en
dc.identifier.uri http://hdl.handle.net/2292/7714 en
dc.description.abstract The potentially bis-terdentate diamide ligand N,N′-bis[2-(2-pyridyl)ethyl]pyrazine-2,3-dicarboxamide (H2LEt) was structurally characterised. Potentiometric titrations revealed rather low pKa values for the deprotonation of the first amide group of H2LEt (14.2) and N,N′-bis(2-pyridylmethyl)pyrazine-2,3-dicarboxamide (H2LMe, 13.1). Two tetranuclear copper(II) square complexes of H2LEt with a paddle-wheel appearance, in which each ligand strand acts as a linear N3–NO hybrid terdentate–bidentate chelate, have been isolated and structurally characterised. Complex [CuII4(H2LEt)2(HLEt)2](BF4)6·3MeCN·0.5H2O (3·3MeCN·0.5H2O), with two nondeprotonated zwitterionic ligand strands and two monodeprotonated ligand strands, is formed in the 1 : 1 reaction of H2LEt and Cu(BF4)2·4H2O. It has a polymeric chain structure of tetranuclear subunits connected by N–HN hydrogen bonds. The same reaction carried out with one equivalent of base gives the related compound [CuII4(HLEt)4](BF4)4 (4), with all four ligand strands monodeprotonated. It consists of isolated tetranuclear units. In both 3·3MeCN·0.5 H2O and 4 the copper(II) ions are in five-coordinate N4O environments but the degree of trigonality (τ) differs [3·3MeCN·0.5H2O 0.14 ≤ τ ≤ 0.26; 4τ = 0.45]. Under the same reaction conditions as for 4 but using Ni(BF4)2·6H2O a tetranuclear [2 × 2] grid-type complex, [NiII4(HLEt)4](BF4)·10H2O (5·10H2O), is formed. The structure determination showed that the nickel(II) ions have N6 distorted octahedral coordination spheres and all four ligand strands are monodeprotonated and act as N3–N3 bis-terdentate chelates. Magnetic susceptibility data show that the complexes 3·4H2O, 4 and 5·10H2O exhibit very weak antiferromagnetic spin coupling. The energies and multiplicities of the spin states of 3·4H2O and 4 were determined from the temperature dependence of the magnetic susceptibility and indicate that a singlet state is lowest and the quintet state highest. This is consistent with the X-band EPR spectra of polycrystalline powders of 3·4H2O and 4, measured down to 2.3 K, where the resonances observed at the lowest temperature are due to a triplet state. The g-values of the individual ions of 4 are consistent with the expected dx2−y2 ground state for five-coordinate copper(II) in an approximately square pyramidal configuration. en
dc.language EN en
dc.publisher ROYAL SOC CHEMISTRY en
dc.relation.ispartofseries Dalton Transactions en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. Previously published items are made available in accordance with the copyright policy of the publisher. Details obtained from http://www.sherpa.ac.uk/romeo/issn/1477-9226/ en
dc.rights.uri https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm en
dc.subject COMPLEX en
dc.subject EPR en
dc.subject SOLVENT en
dc.subject ANION en
dc.subject REFINEMENT en
dc.subject CONSTANTS en
dc.title A [2 × 2] nickel(II) grid and a copper(II) square result from differing binding modes of a pyrazine-based diamide ligand en
dc.type Journal Article en
dc.identifier.doi 10.1039/b614796h en
pubs.issue 6 en
pubs.begin-page 633 en
pubs.volume 2007 en
dc.rights.holder Copyright: 2007 The Royal Society of Chemistry en
dc.identifier.pmid 17268596 en
pubs.end-page 645 en
dc.rights.accessrights http://purl.org/eprint/accessRights/RestrictedAccess en
pubs.subtype Article en
pubs.elements-id 73514 en
pubs.record-created-at-source-date 2010-09-01 en
pubs.dimensions-id 17268596 en

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