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

Raúl Díaz-Torres; Guillaume Chastanet; Eric Collet; Elzbieta Trzop; Phimphaka Harding; David J Harding

doi:10.1039/d3sc01495a

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

Chem Sci. 2023 Jun 1;14(26):7185-7191. doi: 10.1039/d3sc01495a. eCollection 2023 Jul 5.

Authors

Raúl Díaz-Torres¹, Guillaume Chastanet², Eric Collet³, Elzbieta Trzop³, Phimphaka Harding⁴, David J Harding⁴

Affiliations

¹ Thammasat University Research Unit in Multifunctional Crystalline Materials and Applications (TU-MCMA), Faculty of Science and Technology, Thammasat University Pathum Thani 12121 Thailand.
² Université de Bordeaux, ICMCB 87 Avenue du Dr A. Schweitzer Pessac F-33608 France.
³ Univ Rennes, CNRS, IPR (Institut de Physique de Rennes) - UMR 6251 F-35000 Rennes France.
⁴ School of Chemistry, Institute of Science, Suranaree University of Technology Nakhon Ratchasima 30000 Thailand david@g.sut.ac.th phimphaka@g.sut.ac.th.

Abstract

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 T_1/2 = 250 K for the EtOH solvate, where complete SCO occurs. 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.