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![]() RADU, Ioana, KRAVTSOV, Victor, BACA, Svetlana, KRAMER, Karl W, DECURTINS, Silvio, LIU, Shi-Xia, REU, Oleg, OSTROVSKY, Sergei M., PALII, Andrew, KLOKISHNER, Sophia I.. Heterometallic hexanuclear {CoII2CoIII2Dy2} pivalate cluster. In: Physical Methods in Coordination and Supramolecular Chemistry, 8-9 octombrie 2015, Chişinău. Chisinau, Republic of Moldova: 2015, XVIII, p. 128. |
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Physical Methods in Coordination and Supramolecular Chemistry XVIII, 2015 |
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Conferința ""Physical Methods in Coordination and Supramolecular Chemistry"" Chişinău, Moldova, 8-9 octombrie 2015 | ||||||
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Pag. 128-128 | ||||||
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A new heterometallic hexanuclear {CoII 2CoIII 2Dy2} compound with composition [Co4Dy2(OH)2(O2CCMe3)8(HO2CCMe3)2(teaH)2(N3)2] · 2(EtOH) (1) has been prepared from the reaction of dinuclear cobalt(II) pivalate with dysprosium(III) nitrate hexahydrate, trietanolamine (teaH3) ligand and sodium azide and characterized by elemental analysis, IR spectroscopy, and thermogravimetric studies. A single-crystal X-ray diffraction analysis showed that compound 1 crystallizes in the tetragonal space group I41/a and comprises neutral centrosymmetric clusters and crystallization ethanol molecules. The cluster is composed of two CoII, two diamagnetic CoIII , and two DyIII ions bridged by two 3-hydroxy groups, two azide N3 anions, six bridging pivalate residues and additionally linked by two doubly deprotonated teaH2 ligands (Fig. 1). The neutral monodentate pivalic acid and chelating pivalate ion additionally cupped each of the DyIII centers. All cobalt atoms have an octahedral surrounding: NO5 for CoII and N2O4 for CoIII centers. The Dy atoms have a square-antiprismatic O8 geometry. A model for description of the magnetic properties of the obtained cluster has been developed. The model takes into account the crystal fields acting on the DyIII ions and the exchange interaction in the pairs CoIIDyIII and CoIICoII. The Stark structure of the ground 6H15/2 multiplet of the DyIII ions is calculated in the exchange charge model of the crystal field with allowance for covalence effects. The magnetic susceptibility and magnetization are well reproduced in the low temperature range T < 100 K (Fig. 2), projecting the exchange interaction between the CoII and DyIII ions onto the basis representing the direct product of the Kramers doublet ground state for the CoII ions and all Stark levels of the DyIII ions.Fig. 1. Structure of the {CoII 2CoIII 2Dy2} cluster. Fig. 2. χT vs. T and magnetization vs. external magnetic field (T=1.9 K) for the {CoII 2CoIII 2Dy2} cluster: experiment circles, theory solid lines. At higher temperatures the magnetic susceptibility is not affected by the exchange interaction in the CoII-DyIII and CoII-CoII pairs due to its smallness as compared with kT, and good agree-ment between the calculated and experimental χT data is achieved taking into account the population of the Stark levels of the DyIII ions and all spin-orbital multiplets for the CoII ions. |
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