Improving spin crossover characteristics in heteroleptic [FeIII(qsal-5-I)(qsal-5-OMe)]A complexes

Raúl Díaz-Torres; Silvia Gómez-Coca; Eliseo Ruiz; Phimphaka Harding; David J Harding

doi:10.1039/d3dt02503a

Improving spin crossover characteristics in heteroleptic [Fe^III(qsal-5-I)(qsal-5-OMe)]A complexes

Dalton Trans. 2023 Dec 12;52(48):18148-18157. doi: 10.1039/d3dt02503a.

Authors

Raúl Díaz-Torres¹, Silvia Gómez-Coca², Eliseo Ruiz², Phimphaka Harding³, David J Harding³

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 Departament de Química Inorgànica i Orgànica, Institut de Recerca de Química Teòrica i Computacional, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain.
³ School of Chemistry, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand. david@g.sut.ac.th.

PMID: 37908189
DOI: 10.1039/d3dt02503a

Abstract

A family of heteroleptic spin crossover (SCO) [Fe^III(qsal-5-I)(qsal-5-OMe)]A·sol (qsal-5-X = 5-X-2-[(8-quinolylimino)methyl]phenolate; A = NO₃^-1 sol = 2MeOH, NCS^-2 sol = 0.75MeOH·1.3H₂O, BF₄^-3 sol = MeOH, OTf^-4, sol = MeOH) complexes have been synthesized. Most of the complexes exhibit gradual SCO, with the exception of NCS, which is principally high spin. In contrast, the OTf complex shows an abrupt hysteretic SCO (35 K) after solvent loss. The magnetic properties of this complex are significantly improved in comparison to the related homoleptics, [Fe(qsal-I)₂]OTf 5 (hysteresis, 8 K) and [Fe(qsal-5-OMe)₂]OTf·CH₂Cl₂6 (gradual SCO). Structural studies reveal that slight changes in the crystal packing cause stronger interactions improving the cooperativity. These findings are supported by DFT calculations using the r²SCAN functional in which the calculated structures show that SCO from the LS to the HS state causes pronounced scissoring of the 1D π-π chains and substantial changes in their relative orientation following loss of MeOH.