Wang Yu-Ling, Han Chang-Bao, Zhang Yi-Quan, Liu Qing-Yan, Liu Cai-Ming, Yin Shun-Gao
College of Chemistry and Chemical Engineering, Jiangxi Normal University , Nanchang, Jiangxi 330022, P. R. China.
Jiangsu Key Laboratory for NSLSCS, School of Physical Science and Technology, Nanjing Normal University , Nanjing 210023, P. R. China.
Inorg Chem. 2016 Jun 6;55(11):5578-84. doi: 10.1021/acs.inorgchem.6b00653. Epub 2016 May 17.
A series of dinuclear Dy(III) compounds with the general formula [Dy2(μ2-anthc)4(anthc)2(L)2] (anthc(-) = 9-anthracenecarboxylate, L = 2,2'-bipyridyl (1), 1,10-phenanthroline (2), and 4,7-dimethyl-1,10-phenanthroline (3)) were synthesized and magnetically characterized. These compounds exhibit single-molecule magnet (SMM) behavior in the absence of the direct-current field, which is rarely observed for carboxylate-bridged dinuclear Dy2 system. With the first coordination sphere of Dy(III) centers being fixed, the energy barrier was modulated by sequentially modifying the terminal neutral L ligands in this Dy2 system. Theoretical calculations revealed that the symmetry of the charge distribution surrounding the Dy(III) centers in 1-3 is the decisive factor to determine the relaxation of the SMMs. The combination of the larger charge distribution along the magnetic axis and lower charge distribution in the equatorial plane (hard plane) formed by five coplanar coordination atoms including two N atoms provided by an L ligand led to a strong easy-axis ligand field in these compounds. This work presents a rational method to modulate the dynamic magnetic relaxation of the lanthanide SMMs through fine-tuning electrostatic potential of the atoms on the hard plane.
合成并对一系列通式为[Dy2(μ2-anthc)4(anthc)2(L)2]（anthc(-)=9-蒽甲酸根，L = 2,2'-联吡啶(1)、1,10-菲啰啉(2)和4,7-二甲基-1,10-菲啰啉(3)）的双核Dy(III)化合物进行了磁性表征。这些化合物在无直流场的情况下表现出单分子磁体(SMM)行为，这在羧酸根桥联的双核Dy2体系中很少见。在Dy(III)中心的第一配位层固定的情况下，通过依次修饰该Dy2体系中的末端中性L配体来调节能垒。理论计算表明，1-3中Dy(III)中心周围电荷分布的对称性是决定SMM弛豫的决定性因素。由L配体提供的两个N原子在内的五个共面配位原子形成的沿磁轴较大的电荷分布和赤道平面（硬平面）较低的电荷分布相结合，导致这些化合物中形成强的易轴配体场。这项工作提出了一种通过微调硬平面上原子的静电势来调节镧系SMM动态磁弛豫的合理方法。
