Sanakis Yiannis, Krzystek J, Maganas Dimitrios, Grigoropoulos Alexios, Ferentinos Eleftherios, Kostakis Marios G, Petroulea Vasiliki, Pissas Michael, Thirunavukkuarasu Komalavalli, Wernsdorfer Wolfgang, Neese Frank, Kyritsis Panayotis
Institute of Nanoscience and Nanotechnolgy, National Centre of Scientific Research "Demokritos", Aghia Paraskevi 15310, Attiki, Greece.
National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States.
Inorg Chem. 2020 Sep 21;59(18):13281-13294. doi: 10.1021/acs.inorgchem.0c01636. Epub 2020 Sep 8.
The high-spin = 2 Mn(III) complex [Mn{(OPPh)N}] () exhibits field-induced slow relaxation of magnetization ( , , 12869). Magnetic susceptibility and dual-mode X-band electron paramagnetic resonance (EPR) studies revealed a negative value of the zero-field-splitting (zfs) parameter . In order to explore the magnetic and electronic properties of in detail, a combination of experimental and computational studies is presented herein. Alternating-current magnetometry on magnetically diluted samples (/) of in the diamagnetic gallium analogue, [Ga{(OPPh)N}], indicates that the slow relaxation behavior of is due to the intrinsic properties of the individual molecules of . Investigation of the single-crystal magnetization of both and / by a micro-SQUID device reveals hysteresis loops below 1 K. Closed hysteresis loops at a zero direct-current magnetic field are observed and attributed to fast quantum tunneling of magnetization. High-frequency and -field EPR (HFEPR) spectroscopic studies reveal that, apart from the second-order zfs terms ( and ), fourth-order terms () are required in order to appropriately describe the magnetic properties of . These studies provide accurate spin-Hamiltonian (sH) parameters of , i.e., zfs parameters || = 3.917(5) cm, || = 0.018(4) cm, = = 0, and = (3.6 ± 1.7) × 10 cm and = [1.994(5), 1.996(4), 1.985(4)], and confirm the negative sign of . Parallel-mode X-band EPR studies on / and CHCl solutions of probe the electronic-nuclear hyperfine interactions in the solid state and solution. The electronic structure of is investigated by quantum-chemical calculations by employing recently developed computational protocols that are grounded on ab initio wave function theory. From computational analysis, the contributions of spin-spin and spin-orbit coupling to the magnitude of are obtained. The calculations provide also computed values of the fourth-order zfs terms , as well as those of the and hyperfine interaction tensor components. In all cases, a very good agreement between the computed and experimentally determined sH parameters is observed. The magnetization relaxation properties of are rationalized on the basis of the composition of the ground-state wave functions in the absence or presence of an external magnetic field.
高自旋 = 2 的锰（III）配合物[Mn{(OPPh)N}]（）表现出磁场诱导的磁化强度缓慢弛豫（，，12869）。磁化率和双模X波段电子顺磁共振（EPR）研究揭示了零场分裂（zfs）参数的负值。为了详细探究的磁学和电子性质，本文结合了实验和计算研究。在抗磁性镓类似物[Ga{(OPPh)N}]中对进行磁稀释样品（/）的交流磁化率测量表明，的缓慢弛豫行为归因于单个分子的固有性质。通过微超导量子干涉装置对和/的单晶磁化强度进行研究，发现在1 K以下存在磁滞回线。在零直流磁场下观察到闭合的磁滞回线，并将其归因于磁化强度的快速量子隧穿。高频和高场EPR（HFEPR）光谱研究表明，除了二阶zfs项（和）外，还需要四阶项（）才能恰当地描述的磁学性质。这些研究提供了准确的自旋哈密顿量（sH）参数，即zfs参数|| = 3.917(5) cm，|| = 0.018(4) cm， = = 0，以及 = (3.6 ± 1.7) × 10 cm和 = [1.994(5), 1.996(4), 1.985(4)]，并证实了的负号。对/和的CHCl溶液进行的平行模式X波段EPR研究探测了固态和溶液中的电子 - 核超精细相互作用。通过采用基于从头算波函数理论的最新开发的计算协议，通过量子化学计算研究了的电子结构。通过计算分析，获得了自旋 - 自旋和自旋 - 轨道耦合对大小的贡献。计算还提供了四阶zfs项以及和超精细相互作用张量分量的计算值。在所有情况下，计算得到的和实验测定的sH参数之间都观察到了非常好的一致性。基于在有无外部磁场情况下基态波函数的组成，对的磁化弛豫性质进行了合理化解释。
