posted on 2024-02-27, 19:15authored byYing-Ying Wu, Zhao-Yang Li, Shuang Peng, Zi-Yi Zhang, Hao-Ming Cheng, Hang Su, Wen-Qi Hou, Feng-Lei Yang, Shu-Qi Wu, Osamu Sato, Jing-Wei Dai, Wei Li, Xian-He Bu
Spin-crossover
(SCO) materials exhibit remarkable potential as
bistable switches in molecular devices. However, the spin transition
temperatures (Tc) of known compounds are
unable to cover the entire ambient temperature spectrum, largely limiting
their practical utility. This study reports an exemplary two-dimensional
SCO solid solution system, [FeIII(H0.5LCl)2–2x(H0.5LF)2x]·H2O (H0.5LX = 5-X-2-hydroxybenzylidene-hydrazinecarbothioamide, X = F or Cl, x = 0 to 1), in which the adjacent layers are adhered via hydrogen
bonding. Notably, the Tc of this system
can be fine-tuned across 90 K (227–316 K) in a linear manner
by modulating the fraction x of the LF ligand. Elevating x results in strengthened hydrogen bonding between
adjacent layers, which leads to enhanced intermolecular interactions
between adjacent SCO molecules. Single-crystal diffraction analysis
and periodic density functional theory calculations revealed that
such a special kind of alteration in interlayer interactions strengthens
the FeIIIN2O2S2 ligand
field and corresponding SCO energy barrier, consequently resulting
in increased Tc. This work provides a
new pathway for tuning the Tc of SCO materials
through delicate manipulation of molecular interactions, which could
expand the application of bistable molecular solids to a much wider
temperature regime.