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Bright Ratiometric Fluorescent Thermometer in a Spin Crossover Molecule toward Visualization of Spin-State Equilibria
Binbin Wang1, Joseph Kfoury2, Zijian Gong1
1Department of Chemistry, Key Laboratory of Surface & Interface Science of Polymer Materials of Zhejiang Province, Zhejiang Sci-Tech University, Hangzhou 310018, China.
Journal of the American Chemical Society
|January 21, 2026
Summary
Researchers developed a new ratiometric fluorescent probe for spin crossover molecules. This probe enables accurate readout of molecular spin states, crucial for advancing single-molecule magnetic devices.
Area of Science:
- Molecular Spintronics
- Supramolecular Chemistry
- Materials Science
Background:
- Controlling and detecting weak magnetic moments at the single-molecule level requires advanced techniques.
- Accurate readout of molecular spin states by luminescent probes necessitates high signal-to-noise ratio (SNR) and sensitivity.
Purpose of the Study:
- To design and implement a molecular system for optically addressing and detecting molecular spin states.
- To achieve sensitive and accurate ratiometric fluorescent readout of spin crossover (SCO) molecule states.
Main Methods:
- Incorporation of a naphthalimide-based donor-acceptor (D-A) ratiometric fluorescent (RF) probe into a spin crossover (SCO) molecule.
- Utilizing dual emission channels (locally excited and intramolecular charge-transfer states) of the RF probe.
- Exploiting the spectral overlap between SCO thermochromism and the probe's RF bands for a synergistic effect.
Main Results:
- Development of ratiometric fluorescent thermometers (RFTs) with 1.35% K-1 sensitivity and 66% fluorescence contrast.
- Maintained bright fluorescence thermochromism (∼50% quantum yield) throughout the SCO process.
- Enabled direct visualization of spin-state equilibria with high SNR (>400) and detection resolution (0.0017) at low concentrations (10-4 M).
Conclusions:
- Tuning single-fluorophore RF against SCO thermochromism offers a novel platform for molecular spin state readout.
- The developed system provides a high SNR and sensitive method for optically addressing molecular spins.
- This approach advances the design of molecular magnetic devices at the single-molecule level.
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