Bidirectional photoswitchability in an iron(III) spin crossover complex: Symmetry-breaking and solvent effects

15 March 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


The impact of solvent on spin crossover (SCO) behaviour is reported in two solvates [Fe(qsal-I)2]NO3.2ROH (qsal-I = 4-iodo-2-[(8-quinolylimino)methyl]phenolate; R = Me 1 or Et 2) which undergo abrupt and gradual SCO, respectively. A symmetry-breaking phase transition due to spin-state ordering from a [HS] to [HS-LS] state occurs at 210 K in 1, while T1/2 = 250 K for the EtOH solvate. The MeOH solvate exhibits LIESST and reverse-LIESST from the [HS-LS] state, revealing a hidden [LS] state. Moreover, photocrystallographic studies on 1 at 10 K reveal re-entrant photoinduced phase transitions to a high symmetry [HS] phase when irradiated at 980 nm or a high symmetry [LS] phase after irradiation at 660 nm. This study represents the first example of bidirectional photoswitchability and subsequent symmetry-breaking from a [HS-LS] state in an iron (III) SCO material, opening the door to more complex photomagnetic devices.


Spin crossover
iron(III) complexes
crystal structures

Supplementary materials

Supplementary information
Experimental, crystallographic details, structural pictures, TGA and PXRD


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