Stimuli-Responsive Low-Frequency Terahertz Absorption ON-OFF Switchability in Spin-Crossover Material.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 40556593.
- Also identified by DOI 10.1002/adma.202507457 and PMC identifier 12464634.
- Licence recorded as CC BY-NC.
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Abstract
Thermal and optical-induced ON-OFF switchable materials show vast potential in various fields like sensors, spintronics, and electronic devices, but remain underexplored in the essential terahertz (THz) region. In this context, a unique 1D spin-crossover (SCO) network, {[Fe<sup>II</sup>(4-cyanopyridine)<sub>2</sub>][Hg<sup>II</sup>(µ-SCN)<sub>2</sub>(SCN)(4-cyanopyridine)]<sub>2</sub>}<sub>n</sub> (1), has been designed. Temperature-dependent crystallographic, magnetic, and THz absorption spectroscopic studies indicate an abrupt SCO phenomenon from a high-spin (HS) state to a complete or partial low-spin (LS) state, depending on the cooling rate. At low temperatures, the LS state can be converted into the metastable HS state via the light-induced excited spin-state trapping (LIESST) effect using visible or near-infrared lights. Both temperature and light reversibly modulate the THz absorbance (e.g., 0.82 and 1.37 THz) associated with phonons around Fe(II) centers, confirmed by first-principles calculations and photocrystallographic analysis. This work advances comprehension of the intersection between structures, THz properties, and external-stimuli switching effects and is pivotal for future THz device applications.