Comparison of the Magnetic Anisotropy and Spin Relaxation Phenomenon of Dinuclear Terbium(III) Phthalocyaninato Single-Molecule Magnets Using the Geometric Spin Arrangement
Comparison of the Magnetic Anisotropy and Spin Relaxation Phenomenon of Dinuclear Terbium(III) Phthalocyaninato Single-Molecule Magnets Using the Geometric Spin Arrangement
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DOI：
10.1021/jacs.7b12667
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发表时间：
2018-02-28
影响因子：
15
通讯作者：
Yamashita, Masahiro
中科院分区：
文献类型：
--
作者：
Morita, Takaumi;Damjanovic, Marko;Yamashita, Masahiro
本文报道了一种双核TbIII单分子磁体（SMM）的合成和表征，该磁体由两个[TbPc 2]（0）单元通过一个稠合酞菁配体连接而成。通过同步辐射测量和其他光谱技术（ESI-MS、FT-IR、UV）表征了稳定且稳健的配合物[（obPc）Tb（Fused-Pc）Tb（obPc）]（1）。通过密度泛函理论（DFT）研究了Tb-III离子与1中两个π自由基之间的磁耦合。对1的磁稀释和未稀释样品进行直流和交流磁化率测量，表明该化合物是与众所周知的[TbPc 2]（-/0/+）和轴对称双核Tb-III酞菁三层络合物（Tb-2（obPc）（3））相比具有改进性质的SMM。假设在一个TbPc 2单元中发生磁化（QTM）的量子隧穿的概率为P-QTM，则在1中同时发生QTM的概率为P-QTM（2），这意味着QTM被有效地抑制。此外，未稀释的样品1经历缓慢的磁弛豫时间（τ在0.1 K下约为1000 s），并且阻断温度（T-B）被确定为约100 ℃。由于D-4d几何结构和作为交换偏置（H偏置）的弱分子间和分子内磁相互作用，自旋反转（U-eff）的能垒为588 cm（-1）（847 K），降低了QTM。用micro-SQUID测量观察到四个超精细台阶。此外，溶液NMR测量（一维，二维，和动态）进行1，这导致的obPc配体的高旋转势垒（83 +/-10 kJ/mol）的测定。与以前报道的Tb-III三层化合物的比较表明，环境温度NMR测量可以表明SMMs的配位环境的设计改进。大的U-eff在1中引起强的单轴磁各向异性，导致chi（ax）值（1.39 x 10（-30）m（3））大于Tb-2（obPc）（3）（0.86 x 10（-30）m（3））。控制配位环境和自旋排列是抑制TbPc 2基SMM中QTM的有效技术
Herein we report the synthesis and characterization of a dinuclear TbIII single-molecule magnet (SMM) with two [TbPc2](0) units connected via a fused-phthalocyaninato ligand. The stable and robust complex [(obPc)Tb(Fused-Pc)Tb(obPc)] (1) was characterized by using synchrotron radiation measurements and other spectroscopic techniques (ESI-MS, FT-IR, UV). The magnetic couplings between the Tb-III ions and the two pi radicals present in 1 were explored by means of density functional theory (DFT). Direct and alternating current magnetic susceptibility measurements were conducted on magnetically diluted and nondiluted samples of 1, indicating this compound to be an SMM with improved properties compared to those of the well-known [TbPc2](-/0/+) and the axially symmetric dinuclear Tb-III phthalocyaninato triple-decker complex (Tb-2(obPc)(3)). Assuming that the probability of quantum tunneling of the magnetization (QTM) occurring in one TbPc2 unit is P-QTM, the probability of QTM simultaneously occurring in 1 is P-QTM(2), meaning that QTM is effectively suppressed. Furthermore, nondiluted samples of 1 underwent slow magnetic relaxation times (tau approximate to 1000 s at 0.1 K), and the blocking temperature (T-B) was determined to be ca. 16 K with an energy barrier for spin reversal (U-eff) of 588 cm(-1) (847 K) due to D-4d geometry and weak inter- and intramolecular magnetic interactions as an exchange bias (H-bias), reducing QTM. Four hyperfine steps were observed by micro-SQUID measurement. Furthermore, solution NMR measurements (one-dimensional, two-dimensional, and dynamic) were done on 1, which led to the determination of the high rotation barrier (83 +/- 10 kJ/mol) of the obPc ligand. A comparison with previously reported Tb-III triple-decker compounds shows that ambient temperature NMR measurements can indicate improvements in the design of coordination environments for SMMs. A large U-eff causes strong uniaxial magnetic anisotropy in 1, leading to a chi(ax) value (1.39 x 10(-30) m(3)) that is larger than that for Tb-2(obPc)(3) (0.86 x 10(-30) m(3)). Controlling the coordination environment and spin arrangement is an effective technique for suppressing QTM in TbPc2-based SMMs