Rinehart Jeffrey D, Long Jeffrey R
Department of Chemistry, University of California, Berkeley, California 94720-1460, USA.
J Am Chem Soc. 2009 Sep 9;131(35):12558-9. doi: 10.1021/ja906012u.
Results of ac magnetic susceptibility measurements performed on the trigonal prismatic complex U(Ph(2)BPz(2))(3) demonstrate the presence of slow magnetic relaxation under zero applied dc field. Analysis of both the temperature and frequency dependence of the ac susceptibility indicate a temperature regime (T > approximately 3 K) where Arrhenius behavior dominates the relaxation processes, leading to a spin relaxation barrier of U(eff) = 20 cm(-1). The dc-field dependence of the relaxation time was studied to reveal evidence of quantum tunneling processes occurring at lower temperatures. The results suggest a general strategy for identifying further uranium(III)-based single-molecule magnets by concentrating the ligand-field contributions above and below the equatorial plane of an axially symmetric coordination complex.
对三角棱柱配合物U(Ph(2)BPz(2))(3)进行交流磁化率测量的结果表明，在零外加直流磁场下存在缓慢的磁弛豫现象。对交流磁化率的温度和频率依赖性进行分析表明，在一个温度区间（T > 约3 K）内，阿仑尼乌斯行为主导着弛豫过程，导致有效自旋弛豫能垒U(eff) = 20 cm(-1)。研究了弛豫时间与直流磁场的依赖性，以揭示在较低温度下发生的量子隧穿过程的证据。结果表明了一种通用策略，即通过集中轴对称配位配合物赤道面上下的配体场贡献来识别更多基于铀(III)的单分子磁体。
