Akiyoshi Ryohei, Komatsumaru Yuki, Donoshita Masaki, Dekura Shun, Yoshida Yukihiro, Kitagawa Hiroshi, Kitagawa Yasutaka, Lindoy Leonard F, Hayami Shinya
Department of Chemistry, Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan.
Division of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto, 606-8502, Japan.
Angew Chem Int Ed Engl. 2021 Jun 1;60(23):12717-12722. doi: 10.1002/anie.202015322. Epub 2021 Apr 29.
Ferroelectric spin crossover (SCO) behavior is demonstrated to occur in the cobalt(II) complex, Co(FPh-terpy) ⋅3ac (1⋅3 ac; FPh-terpy=4'-((3-fluorophenyl)ethynyl)-2,2':6',2''-terpyridine) and is dependent on the degree of 180° flip-flop motion of the ligand's polar fluorophenyl ring. Single crystal X-ray structures at several temperatures confirmed the flip-flop motion of fluorobenzene ring and also gave evidence for the SCO behavior with the latter behavior also confirmed by magnetic susceptibility measurements. The molecular motion of the fluorobenzene ring was also revealed using solid-state F NMR spectroscopy. Thus the SCO behavior is accompanied by the flip-flop motion of the fluorobenzene ring, leading to destabilization of the low spin cobalt(II) state; with the magnitude of rotation able to be controlled by an electric field. This first example of spin-state conversion being dependent on the molecular motion of a ligand-appended fluorobenzene ring in a SCO cobalt(II) compound provides new insight for the design of a new category of molecule-based magnetoelectric materials.
铁电自旋交叉（SCO）行为被证明发生在钴（II）配合物Co(FPh-terpy)·3ac（1·3 ac；FPh-terpy = 4'-((3-氟苯基)乙炔基)-2,2':6',2''-三联吡啶）中，且取决于配体极性氟苯环180°翻转运动的程度。在几个温度下的单晶X射线结构证实了氟苯环的翻转运动，也为SCO行为提供了证据，后者的行为也通过磁化率测量得到了证实。氟苯环的分子运动也通过固态19F NMR光谱得以揭示。因此，SCO行为伴随着氟苯环的翻转运动，导致低自旋钴（II）态的不稳定；旋转幅度能够由电场控制。这种自旋态转换依赖于SCO钴（II）化合物中配体连接的氟苯环分子运动的首个例子，为设计新型分子基磁电材料提供了新的见解。
