Michaels, E, Capel Berdiell, I orcid.org/0000-0003-3828-7097, Vasili, HB orcid.org/0000-0002-3356-6436 et al. (4 more authors) (2022) Spin-Crossover in a New Iron(II)/Di(pyrazolyl)pyridine Complex with a Terpyridine Embrace Lattice. Thermally Induced Excited Spin State Trapping and Clarification of a Structure−Function Correlation. Crystal Growth and Design, 22 (11). pp. 6809-6817. ISSN 1528-7483
Abstract
The complex salts [FeL2]X2 (1X2; L = 2,6-di{4-fluoropyrazol-1-yl}pyridine; X– = BF4– or ClO4–) exhibit abrupt spin-transitions with narrow thermal hysteresis, at T1/2 = 164 K (X– = BF4–) and 148 K (X– = ClO4–). The transition in 1[ClO4]2 is complicated by efficient thermally induced excited spin-state trapping (TIESST) of its high-spin state below ca. 120 K, and the fully low-spin state was achieved only inside the magnetometer at a scan rate of 0.5 K min–1. Crystals of 1[BF4]2 are tetragonal (P421c, Z = 2; phase 1) at 300 K but transform to a highly twinned monoclinic phase 2 (P21, Z = 2) at 285 ± 5 K. These are forms of the “terpyridine embrace” crystal lattice, which often affords cooperative spin-transitions in iron/di(pyrazolyl)pyridine complexes. Phase 2 of high-spin 1[BF4]2 shows a significant temperature dependence by powder diffraction, which reflects increased canting of the monoclinic unit cell as the temperature is lowered. In contrast, 1[ClO4]2 retains phase 2 between 100 and 300 K, and was crystallographically characterized in its thermally trapped metastable high-spin state at 100 K, as well as its thermodynamic high- and low-spin forms at higher temperatures. The spin-crossover transition temperature in 1[ClO4]2 and related compounds correlates well with a parameter describing angular changes to the metal coordination sphere during the transition but not with other commonly used structural indices. The TIESST metastable high-spin state of 1[ClO4]2 shows no single molecule magnet properties at 2 K.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2022 The Authors. Published by American Chemical Society. This is an open access article under the terms of the Creative Commons Attribution License (CC-BY). |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Chemistry (Leeds) > Inorganic Chemistry (Leeds) The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Physics and Astronomy (Leeds) > Condensed Matter (Leeds) |
Funding Information: | Funder Grant number EPSRC (Engineering and Physical Sciences Research Council) EP/K00512X/1 EPSRC (Engineering and Physical Sciences Research Council) EP/J021156/1 |
Depositing User: | Symplectic Publications |
Date Deposited: | 05 Oct 2022 13:30 |
Last Modified: | 15 Jan 2025 15:45 |
Status: | Published |
Publisher: | American Chemical Society |
Identification Number: | 10.1021/acs.cgd.2c00980 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:191436 |