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The magnetic properties of materials can be modulated by external stimuli through either spin-state transition or modification of the coordination environment. However, achieving both mechanisms in a single-phase system via sophisticated molecular design remains a formidable challenge. In this work, we present an Fe(II) spin-crossover (SCO) complex incorporating rotatable isoxazole ligands, which exhibits a three-step reversible magnetic transition from 120 to 300 K. In this compound, the metal centers experience two-step SCO transition at ca. 147 and 221 K. Upon further heating, the isoxazole ligands undergo significant rotation around the Fe-N coordination bonds, accompanied by an order-disorder phase transition of the ClO counteranions. As the rotation of organic ligand can influence the electron-density delocalization between the aromatic ring and Fe ion, an additional magnetic anomaly arises near 245 K. The use of rotatable ligands to build SCO compounds offers a promising avenue toward superior materials capable of integrating switchable properties that stem from both electronic-state transition and molecular structural changes.
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http://dx.doi.org/10.1021/acs.inorgchem.5c01241 | DOI Listing |
Chem Commun (Camb)
August 2025
Department Chemie, Johannes-Gutenberg-Universität Mainz, Duesbergweg 10-14, 55128 Mainz, Germany.
The influence of chirality on the packing of solids, and consequently on the magnetic behavior of spin crossover (SCO) materials, is well documented. Here, we present an exceptional case involving three iron(II) complexes [Fe(LNaph-ODA-(X)-Al)(NCBH)]·0.5 CHCN (X = racemic (C1), (C2), and (C3)), based on a new 1,3,4-oxadiazole ligand (LNaph-ODA-(X)-Al) with distinct stereocenters.
View Article and Find Full Text PDFChem Asian J
July 2025
Jiangsu Key Laboratory of Green Synthetic Chemistry for Functional Materials, School of Chemistry and Material Science, Jiangsu Normal University, Xuzhou, 221116, China.
Seven new mononuclear complexes [Fe(aqin)(NCS)] (1), [Fe(aqin)(NCSe)] (2), [Fe(aqin)(NCBH)] (3), [Fe(2-pic)(NCS)] (4), [Fe(2-pic)(NCSe)] (5), [Fe(2-pic)(NCBH)] (6), [Fe(tpa)(NCBH)] (7), [aqin = 8-aminoquinoline, 2-pic = 2-picolylamine, tpa = tris(2-pyridylmethyl)amine)] are investigated. Structurally, except for 3, which affords a trans-configuration, all the complexes adopt a cis-configuration. Their propensity to crystallize without any solvent molecules facilitates the study of the influence of the "pure" ligand on spin-crossover (SCO) characteristics.
View Article and Find Full Text PDFNanoscale
July 2025
Department of Chemical Physics & Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China.
Transition metal spin-crossover (SCO) complexes with magnetic bistability show great promise as spin-switches for molecule-based devices. Using first-principles calculations combined with the non-equilibrium Green's function technique, we explored the spin-resolved electronic and transport properties of photochromic Fe(II) SCO complexes in the high-spin state with the open-ring (HS-O) isomer and in the low-spin state with the closed-ring (LS-C) isomer, since the photocyclization and photocycloreversion between the HS-O and LS-C isomers can be reversibly realized under light radiation with different wavelengths at room temperature as in previous experiments. Our results clearly reveal that the examined Fe(II) SCO complexes with photochromic diarylethene-based ligands in the HS-O isomer have lower energy than the LS-C isomer of 0.
View Article and Find Full Text PDFInorg Chem
July 2025
Department of Inorganic and Analytical Chemistry, University of Geneva, 30 quai E. Ansermet, Geneva 4CH-1211, Switzerland.
The efficiency of intermetallic d-f energy transfers in molecular-based Fe(II)-Ln(III) dyads can be modulated by (i) the spin state of the [Fe(II)N] unit, (ii) the intermetallic distance, and (iii) the choice of the trivalent lanthanide (Ln(III)). The programming of a monotonous and reliable change in Ln-based luminescence upon spin-crossover (SCO) processes is highly desired for easy and fast optical monitoring of Fe(II)-spin state, but Ln···Fe separations over the nanometer range are required to be compatible with detectable Ln-based light emission. Moving from a nonluminescent rigid macrobicyclic dinuclear [FeEu()] triple-stranded helicate (Fe···Eu = 9.
View Article and Find Full Text PDFAdv Mater
June 2025
Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
Thermal and optical-induced ON-OFF switchable materials show vast potential in various fields like sensors, spintronics, and electronic devices, but remain underexplored in the essential terahertz (THz) region. In this context, a unique 1D spin-crossover (SCO) network, {[Fe(4-cyanopyridine)][Hg(µ-SCN)(SCN)(4-cyanopyridine)]} (1), has been designed. Temperature-dependent crystallographic, magnetic, and THz absorption spectroscopic studies indicate an abrupt SCO phenomenon from a high-spin (HS) state to a complete or partial low-spin (LS) state, depending on the cooling rate.
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