Spontaneous Chiral Resolution of a MnIII Spin‐Crossover Complex with High Temperature 80 K Hysteresis

• Published in: Chemistry : a European journal 2023-07, Vol.29 (37), p.e202300275-n/a
• Main Authors: Kelly, Conor T., Jordan, Ross, Felton, Solveig, Müller‐Bunz, Helge, Morgan, Grace G.
• Format: Article
• Language: English
• Subjects: Ambient temperature; Chemistry; chiral resolution; Circular dichroism; Crossovers; Dichroism; Electronic structure; Ethane; High temperature; Hydroxybenzaldehydes; Hysteresis; Imines; Isomers; Optical materials; Quantum chemistry; Reagents; Single crystals; spin crossover; Switches; X-ray diffraction
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202300275

Non‐centrosymmetric spin‐switchable systems are of interest for their prospective applications as magnetically active non‐linear optical materials and in multiferroic devices. Chiral resolution of simple spin‐crossover chelate complexes into the Δ and Λ forms offers a facile route to homochiral magnetic switches, which could be easily enantiomerically enriched. Here, we report the spontaneous resolution of a new hysteretic spin‐crossover complex, [MnIII(sal2323)]SCN ⋅ EtOH (1), into Δ and Λ forms, without the use of chiral reagents, where sal2323 is a Schiff base resulting from condensation of 1,2‐bis(3‐aminopropylamino)ethane with 2‐hydroxybenzaldehyde. The enantiopurity of the Δ and Λ isomers was confirmed by single crystal X‐ray diffraction and circular dichroism. Quantum chemistry calculations were used to investigate the electronic structure. The opening of a wide 80 K thermal hysteresis window at high temperature highlights the potential for good magneto‐optical function at ambient temperature for materials of this type. Spontaneous chiral resolution of the Δ and Λ isomers of a racemic mixture of a MnIII spin‐crossover complex is achieved by conglomerate crystallization. The complex exhibits gradual spin crossover with a wide thermal hysteresis, ∼80 K at its maximum, with T1/2↑=250 K and T1/2↓=200 K. Single‐crystal X‐ray diffraction and circular dichroism was used to confirm the enantiopurity of the Δ and Λ isomers.