π-Expansion-Directed Modulation of Spin-Fluorescence Coupling in Spin-Crossover Hofmann-Type Frameworks.

The coupling between spin crossover (SCO) and luminescence provides a direct, noninvasive optical readout of spin-state switching, which is pivotal for the development of advanced molecular sensors, memory devices, and opto-spintronic applications. Herein, we report two two-dimensional Hofmann-type coordination polymers, i.e., {Fe2(PYNA)4[Ag(CN)2]4} (1) and {Fe3(PYAN)6[Ag(CN)2]6}·o-DCB (2, o-DCB = ortho-dichlorobenzene), based on two extended π-conjugated ligands, 4-(2-naphthalenyl)pyridine (PYNA) and 4-(2-anthracenyl)pyridine (PYAN), respectively. Divergent SCO behaviors were observed for the two compounds, as confirmed by temperature-dependent magnetic susceptibility measurements, structural analyses, and differential scanning calorimetry measurements. In addition, light-induced excited spin-state trapping effects were found in the two SCO compounds, and bidirectional photoswitching of spin states can be realized reversibly. Crucially, a comparative variable-temperature fluorescence (FL) study highlights a π-expansion-driven contrast: SCO-FL coupling is operative in 1 but absent in 2. Theoretical calculations directly account for the distinct energy transfer pathways in 1 and 2, rationalizing their contrasting outcomes in achieving SCO-FL coupling. This study provides important support for the precise modulation of the spin-optical coupling properties through ligand engineering.

• Publication year

  2026

• Venue

  Inorganic Chemistry

• Publication date

  2026-01-07

• Fields of study

  Medicine, Materials Science, Chemistry

• Identifiers
  DOI 10.1021/acs.inorgchem.5c05053PMID 41498422
• External record

  Open on Semantic Scholar

• Source metadata

  Semantic Scholar, PubMed

• No claims are published for this paper.

• No concepts are published for this paper.

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