Tetranuclear {CoII2CoIII2} and octanuclear {CoII4CoIII4} aminoalcohol-supported pivalate clusters
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RADU, Ioana; KRAVTSOV, Viktor; OSTROVSKY, Sergei M.; REU, Oleg; KRAMER, Karl W; DECURTINS, Silvio; LIU, Shixia; KLOKISHNER, Sophia; BACA, Svetlana. Tetranuclear {CoII2CoIII2} and octanuclear {CoII4CoIII4} aminoalcohol-supported pivalate clusters. In: Materials Science and Condensed Matter Physics. Editia a 8-a, 12-16 septembrie 2016, Chişinău. Chişinău: Institutul de Fizică Aplicată, 2016, p. 137. ISBN 978-9975-9787-1-2.
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Materials Science and Condensed Matter Physics
Editia a 8-a, 2016
Conferința "International Conference on Materials Science and Condensed Matter Physics"
8-th Edition, Chişinău, Moldova, 12-16 septembrie 2016

Tetranuclear {CoII2CoIII2} and octanuclear {CoII4CoIII4} aminoalcohol-supported pivalate clusters


Pag. 137-137

Radu Ioana1, Kravtsov Viktor1, Ostrovsky Sergei M.1, Reu Oleg1, Kramer Karl W2, Decurtins Silvio2, Liu Shixia2, Klokishner Sophia1, Baca Svetlana1
 
1 Institute of Applied Physics, Academy of Sciences of Moldova,
2 Department of Chemistry and Biochemistry, University of Bern
 
Disponibil în IBN: 29 iulie 2019


Rezumat

Over the last decades, the preparation and investigation of compounds based on high-nuclearity 3d clusters have attracted much interest since these magnetic materials are perspective for diverse applications ranging from high-density information storage devices to molecular electronics. In continuation of our research on the construction of carboxylate clusters with interesting magnetic properties a simple route to new mixed-valent tetranuclear [NaCo4(piv)6(Hpiv)2(teaH)2(N3)] (1) and octanuclear [Co8(piv)10(teaH)4(N3)](piv)∙(MeCN)∙(H2O) (2) clusters from a dinuclear pivalate CoII precursor [Co2(--OH)2(piv)4(Hpiv)4] and triethanolamine ligand (teaH3) has been developed. The prepared clusters have been characterized by a range of physical methods including IR/Raman, thermogravimetrical analysis, and magnetic studies. Single-crystal X-ray analysis reveals that the asymmetric unit of 1 contains four neutral [NaCo4(piv)6(Hpiv)2(teaH)2(N3)] clusters. The clusters consist of four Co atoms bridged by four piv-, two bridging teaH2- ligands and one N3- azide to form a calix-like tetranuclear unit capped with a Na+ and two Hpiv. Two pivalate ligands additionally bridge Co atoms and an apical Na center. Within the Co4 core, two Co atoms are in the oxidation state +2, whereas two other Co in the oxidation state +3. Complex 2 consists of a cationic [Co8(piv)10(teaH)4(N3)]+ cluster, a pivalic anion and crystallization MeCN and H2O molecules. As shown in Figure, [Co8(piv)10(teaH)4(N3)]+ comprises a central Co4 core in which the metal ions reside in the vertexes of a flatten tetrahedron and are joined by a -4-azide and four bridging pivalate residues. These Co atoms are in the oxidation state +2. Four pivalate ligands are --bridging the central CoII4 atoms to four outer diamagnetic CoIII centers together with four teaH2-. Finally, two bridging pivalates complete the coordination sphere of CoIII atoms. The structure analysis demonstrates that the magnetic properties of the cluster are determined by two CoII dimers. The model for the description of the magnetic characteristics of the obtained octanuclear cluster includes its interaction with the external magnetic field, the zero-field splitting term for the CoII ions possessing an orbitally degenerate ground state in the pentanuclear ligand surrounding and the relatively strong exchange interaction within each of the CoII dimers that is mediated by the bridging nitrogen. The exchange coupling between the CoII ions belonging to different dimers is neglected since it is expected to be much weaker due to the long interdimer bridge consisting of three N atoms. During the calculation of the magnetic susceptibility of the cluster the contribution of the temperature independent magnetism has been taken into account as well. Within the framework of the developed model quite a good agreement is obtained between the calculated and observed values of the magnetic susceptibility as a function of temperature and magnetization as a function of the external magnetic field.