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SM ISO690:2012 LEVCHENKOV, S., POPOV, Leonid, SHCHERBAKOV, Igor, SUPONITSKY, Kyrill, BELOBORODOV, S., TSATURYAN, A., LUKOV, V., KOGAN, V.. The unique tetranuclear copper(II) complex with azomethine ligand: the crystal structure and magnetic properties. In: Physical Methods in Coordination and Supramolecular Chemistry, 24-26 octombrie 2012, Chişinău. Chisinau, Republic of Moldova: 2012, XVII, p. 101. |
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Physical Methods in Coordination and Supramolecular Chemistry XVII, 2012 |
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Conferința ""Physical Methods in Coordination and Supramolecular Chemistry"" Chişinău, Moldova, 24-26 octombrie 2012 | |||||
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Pag. 101-101 | |||||
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The unique tetranuclear copper(II) complex with azomethine ligand produced by the condensation of 1-phenyl-3-methyl-4-formyl-5-hydroxy-pyrazole and 1,3-diaminopropan-2- ol has been synthesized und studied. Crystals of the complex contain two non-equivalent molecules with non-trivial cubane-like structure with the molar ratio 2:1. One of the molecules has unsymmetrical (A) and another one – symmetrical (B) Cu4N2O2 exchange core.figureThe magnetic measurements revealed the lowering of magnetic moment calculated per one copper(II) atom from 1.49 B.M. down to 0.42 B.M. in the temperature range 300 – 2 K. This behavior is indicative of a dominant antiferromagnetic coupling that results in a singlet (S = 0) spin ground state. Some paramagnetic impurities (S = ½) make the μeff vs. T curve to deviate from 0 at low temperatures. The theoretical treatment of exchange interaction is rather complicated in this case due to the different structures of A and B exchange fragments. Indeed the exchange Hamiltonian should include at least three different exchange parameters for both types of molecules. Under this approach the magnetic properties of each tetranuclear core of the complex should be analyzed by means of the following zero-field spin Hamiltonian: The magnetic susceptibility expression for such a system can be obtained as follows: , where χA and χB are the magnetic susceptibility of non-symmetrical and symmetrical tetranuclear clusters, correspondingly, and f is the molar ratio of paramagnetic impurity. The best-fitted set of exchange parameters is: J1A = –8 см–1 , J2A = -63 сm–1 , J3A = -175 сm–1 , J1B = –34 сm–1 , J2B = –67 сm–1 , J3B = 38 сm–1 , g = 2.05, f = 0.047, R (mean-square error) 0.051. The quantum-chemical calculation based on “broken symmetry” approach revealed good agreement between theoretical and experimental data |
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