Zenno Hikaru, Sekine Yoshihiro, Zhang Zhongyue, Hayami Shinya
Department of Chemistry, Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto 860-8555, Japan.
Priority Organization for Innovation and Excellence, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto 860-8555, Japan.
Dalton Trans. 2024 Mar 26;53(13):5861-5870. doi: 10.1039/d3dt03936f.
Coexistence and switching between spin-crossover (SCO) and single molecular magnet (SMM) behaviours in one single complex may lead to materials that exhibit bi-stable and stimuli sensitive properties in a wide temperature range and under multiple conditions; unfortunately, the conflict and dilemma in the principle of approaching SCO and SMM molecules make it particularly difficult; at low temperature, low spin (LS) SCO molecules possess highly symmetrical geometry and isotropic spins, which are not suitable for SMM behaviour. Herein, we overcome this issue by using a rationally designed Co(II) mononuclear complex [Co(MeOphterpy)] (ClO) (1; MeOphterpy = 4'-(4-methoxyphenyl)-2,2':6',2''-terpyridine), the magnetic properties of which reversibly respond to desolvation and solvation. The solvated structure reinforced a low distortion of the coordination sphere hydrogen bonding between ligands and methanol molecules, while in the desolvated structure a methoxy group flipping occurred, increasing the distortion of the coordination sphere and stabilising the HS state at low temperature, which exhibited a field-induced slow magnetic relaxation, resulting in a reversible switching between SCO and SMM properties within one molecule.
在单一配合物中自旋交叉（SCO）和单分子磁体（SMM）行为的共存与转换，可能会产生在宽温度范围和多种条件下表现出双稳态和刺激敏感特性的材料；不幸的是，接近SCO和SMM分子原理中的冲突与困境使其尤为困难；在低温下，低自旋（LS）SCO分子具有高度对称的几何结构和各向同性的自旋，这不适用于SMM行为。在此，我们通过使用合理设计的Co（II）单核配合物[Co（MeOphterpy）]（ClO）（1；MeOphterpy = 4'-（4-甲氧基苯基）-2,2':6',2''-三联吡啶）克服了这个问题，其磁性能对去溶剂化和溶剂化有可逆响应。溶剂化结构增强了配位球的低畸变——配体与甲醇分子之间的氢键作用，而在去溶剂化结构中发生了甲氧基翻转，增加了配位球的畸变并在低温下稳定了高自旋（HS）态，这表现出场诱导的慢磁弛豫，导致在一个分子内SCO和SMM性质之间的可逆转换。
