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
作者: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
DOI:10.1007/s11172-010-0152-x
日期:2010.4
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 μeff(T) is observed at T < 60 K. A nonmonotonic increase in μeff(?) for 1 (s~6 %) and a 20% reduction of μeff(?) 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 μeff(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.
研究人员合成了 CuII 与 3-(3,5-二甲基吡唑-1-基)-6-(2-羟乙基氨基)-1,2,4,5-四嗪 (1) 的双核配合物,以及 CoII 与 3-(3,5-二甲基吡唑-1-基)-6-(哌啶-1-基)-1,2,4,5-四嗪 (2) 的双核配合物、5- tetrazine (2) 进行了合成和结构表征,并研究了基于这些配合物的范德华晶体的磁性(SQUID)和共振(EPR)特性。1的μeff(?)非单调增加(s~6%)和2的μeff(?)减少20%有着共同的原因,都是由于自旋轨道耦合对中心离子的t2g和eg电平之间分裂特性的影响。配位位点的畸变在 6 K 附近 "开启 "了轨道磁矩的正(1)或负(2)贡献。μeff(T) 在 60 K 附近的加热和冷却状态下的不可逆温度行为表明,结构畸变的特征和磁性与配体的几何形状有关。这一因素在多氮配体磁活性结构的晶体工程中发挥着重要作用。