S 98 Synthesis, structures, and magnetic properties of crystals of dinuclear copper(II) and cobalt(II) complexes with 3-(3,5-dimethylpyrazol-1-yl)-6-R-1,2,4,5-tetrazines [Electronic resource] / E. V. Cherdantseva, D. V. Starichenko, P. A. Slepukhin, R. I. Ishmetova, Yu. N. Shvachko, A. V. Korolev, G. L. Rusinov, V. V. Ustinov, A. I. Matern, V. N. Charushin // Russian Chemical Bulletin (Translation of Izvestiya Akademii Nauk, Seriya Khimicheskaya). - 2010. - Vol. 59, № 4. - P717-723 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): DINUCLEAR COMPLEXES -- SPIN MAGNETISM -- TETRAZINES Аннотация: Dinuclear complexes of CuII with 3-(3,5-dimethylpyrazol-1-yl)-6-(2-hydroxyethylami-no)-1,2,4,5-tetrazine (1) and CoII with 3-(3,5-dimethylpyrazol-1-yl)-6-(piperidin-1-yl)-1,2,4,5- tetrazine (2) were synthesized and structurally characterized, and the magnetic (SQUID) and resonance (EPR) properties of van der Waals crystals based on these complexes were studied. Unusual behavior of the effective magnetic moment ?eff(T) is observed at T < 60 K. A nonmonotonic increase in eff() for 1 (s~6 %) and a 20% reduction of eff for 2 have a common origin and are due to the influence of spin-orbital coupling on the character of the splitting between the t2g and eg levels of the central ion. Distortions of the coordination site “switch on” a positive (1) or negative (2) contribution of the orbital magnetic moment near 6 K. Irreversible temperature behavior of eff(T) in the heating and cooling regimes in the vicinity of 60 K suggests that the character of structural distortions and the magnetic properties are related to ligand geometry. This factor plays a significant role in crystal engineering of magnetoactive structures with polynitrogen ligands \\\\Expert2\\nbo\\Russian Chemical Bulletin\\2010, 59 (4), 717-723.pdf |