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Proton-Induced Spin State Switching in an FeIII Complex.
Conor T Kelly1, Sean Dunne1, Irina A Kühne1
1School of Chemistry, University College Dublin, Belfield, Dublin 4, Ireland.
Angewandte Chemie (International Ed. in English)
|February 16, 2023
Summary
This study reveals reversible spin state switching in an iron(III) complex triggered by acid. This discovery introduces a new class of sensors with magnetic and colorimetric responses.
Area of Science:
- Coordination Chemistry
- Materials Science
- Supramolecular Chemistry
Background:
- Iron(III) complexes can exhibit spin crossover (SCO) behavior, transitioning between low-spin and high-spin states.
- Controlling SCO through external stimuli like pH is crucial for developing responsive materials.
Purpose of the Study:
- To investigate proton-induced reversible spin state switching in iron(III) complexes.
- To explore the potential of these complexes as analyte sensors with magnetic and colorimetric outputs.
Main Methods:
- Synthesis and characterization of iron(III) complexes [Fe(sal2323)]ClO4 (1) and [Fe(4-NEt2-sal2323)]ClO4 (2).
- Magnetic susceptibility measurements using Evans' method.
- Protonation studies using 1H NMR spectroscopy and infrared spectroscopy.
Main Results:
- Complex 1 exhibited reversible spin state switching from low-spin to high-spin upon addition of acid.
- Infrared spectroscopy indicated a coordination-induced spin state switching (CISSS) mechanism.
- Complex 2 showed a combined magnetic and colorimetric response to protonation, demonstrating analyte sensing capabilities.
Conclusions:
- Protonation reversibly switches the spin state of the iron(III) complexes.
- The spin switching is driven by perturbation of the metal's coordination sphere.
- These complexes represent a novel class of magneto-responsive sensors, with potential for dual magnetic and colorimetric detection.
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