Chiral Resolution of Spin‐Crossover Active Iron(II) [2x2] Grid Complexes. Issue 61 (20th July 2021)

• Record Type: Journal Article
• Authors: Suryadevara, Nithin; Pausch, Ansgar; Moreno‐Pineda, Eufemio; Mizuno, Asato; Bürck, Jochen; Baksi, Ananya; Hochdörffer, Tim; Šalitroš, Ivan; Ulrich, Anne S.; Kappes, Manfred M.; Schünemann, Volker; Klopper, Wim; Ruben, Mario
• Is Part Of: Chemistry. Volume 27:Issue 61(2021)
• Page Start: 15172
• Page End: 15180
• Publication Date: 2021-07-20
• Subjects: chirality -- grid complexes -- ion mobility -- Mössbauer spectroscopy -- spin-crossover; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.202101432
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Chiral magnetic materials are proposed for applications in second‐order non‐linear optics, magneto‐chiral dichroism, among others. Recently, we have reported a set of tetra‐nuclear Fe(II) grid complex conformers with general formula C/S‐[Fe4 L4 ] 8+ (L: 2, 6‐bis(6‐(pyrazol‐1‐yl)pyridin‐2‐yl)‐1, 5‐dihydrobenzo[1, 2‐d : 4, 5‐d′]diimidazole). In the grid complexes, isomerism emerges from tautomerism and conformational isomerism of the ligand L, and the S‐type grid complex is chiral, which originates from different non‐centrosymmetric spatial organization of the trans type ligand around the Fe(II) center. However, the selective preparation of an enantiomerically pure grid complex in a controlled manner is difficult due to spontaneous self‐assembly. To achieve the pre‐synthesis programmable resolution of Fe(II) grid complexes, we designed and synthesized two novel intrinsically chiral ligands by appending chiral moieties to the parent ligand. The complexation of these chiral ligands with Fe(II) salt resulted in the formation of enantiomerically pure Fe(II) grid complexes, as unambiguously elucidated by CD and XRD studies. The enantiomeric complexes exhibited similar gradual and half‐complete thermal and photo‐induced SCO characteristics. The good agreement between the experimentally obtained and calculated CD spectra further supports the enantiomeric purity of the complexes and even the magnetic studies. The chiral resolution of Fe(II)‐ [2×2] grid complexes reported in this study, for the first time, might enable the fabrication of magneto‐chiral molecular devices. Abstract : The trans ‐type ligand wrapping around the metal centers in an inter‐woven style makes the complex to be in chiral. This separation of Λ and Δ forms of spin‐crossover isomers was successfully achieved by appending the chiral moiety onto the parent ligand. The presence of spin‐crossover and chirality makes these multifunctional complexes intriguing for the study of magneto‐optical effects.