Linked Life Data

11506562

Source:http://linkedlifedata.com/resource/pubmed/id/11506562

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PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
33
pubmed:dateCreated
2001-8-16
pubmed:abstractText
New dissymmetric tertiary amines (N(3)SR) with varying N/S donor sets have been synthesized to provide mono- and dinuclear complexes. Acetate ions are used to complete the octahedral coordination sphere around nickel(II) atom(s). The facile conversion of mononuclear to dinuclear systems can be controlled to produce either mono- or dinuclear complexes from the same ligand. The dinuclear complex a(BPh(4))(2) ([Ni(2)(N(3)SSN(3))(OAc)(2)](BPh(4))(2)) has been characterized in the solid state by X-ray diffraction techniques as solvate: a(BPh(4))(2).(1/2)[5(CH(3)OH).(CH(3)CN).(CH(3)CH(2)OH)]. The two Ni atoms are six-coordinated and bridged by a disulfide group and two bidentate acetates. Magnetic susceptibility reveals a weak ferromagnetic exchange interaction between the two Ni atoms with J = 2.5(7) cm(-1). UV-vis studies suggest that the six-coordinated structure persists in solution. The (1)H NMR spectrum of a(BPh(4))(2) exhibits sharp significantly hyperfine shifted ligand signals. A complete assignment of resonances is accomplished by a combination of methods: 2D-COSY experiments, selective chemical substitution, and analysis of proton relaxation data. Proton isotropic hyperfine shifts are shown to originate mainly from contact interactions and to intrinsically contain a small J-magnetic coupling and/or zero-field splitting contribution. A temperature dependence study of longitudinal relaxation times indicates that a very unusual paramagnetic Curie dipolar mechanism is the dominant relaxation pathway in these weakly ferromagnetically spin-coupled dinickel(II) centers. The mononuclear nickel(II) analogue exhibits extremely broader (1)H NMR signals and only partial analysis could be performed. These data are consistent with a shortening of electronic relaxation times in homodinuclear compounds with respect to the corresponding mononuclear species.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Aug
pubmed:issn
0002-7863
pubmed:author
pubmed:issnType
Print
pubmed:day
22
pubmed:volume
123
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
8053-66
pubmed:dateRevised
2008-11-21
pubmed:meshHeading
pubmed:year
2001
pubmed:articleTitle
Paramagnetic NMR investigations of high-spin nickel(II) complexes. Controlled synthesis, structural, electronic, and magnetic properties of dinuclear vs. mononuclear species.
pubmed:affiliation
Laboratoire d'Etudes Dynamiques et Structurales de la Sélectivité (LEDSS, UMR CNRS 5616), Université Joseph Fourier, BP 53X, 38041 Grenoble Cedex 9, France. Catherine.Belle@ujf-grenoble.fr
pubmed:publicationType
Journal Article