Cook, LJK, Shepherd, HJ, Comyn, TP et al. (4 more authors) (2015) Decoupled spin crossover and structural phase transition in a molecular iron(II) complex. Chemistry - A European Journal, 21 (12). 4805 - 4816. ISSN 0947-6539
Abstract
Crystalline [Fe(bppSMe) 2][BF4]2 (1 ; bppSMe = 4-(methylsulfanyl)-2,6-di(pyrazol-1-yl)pyridine) undergoes an abrupt spin-crossover (SCO) event at 265 ±5 K. The crystals also undergo a separate phase transition near 205 K, involving a contraction of the unit-cell a axis to one-third of its original value (high-temperature phase 1; Pbcn, Z = 12; lowtemperature phase 2; Pbcn, Z = 4). The SCO-active phase 1 contains two unique molecular environments, one of which appears to undergo SCO more gradually than the other. In contrast, powder samples of 1 retain phase 1 between 140-300 K, although their SCO behaviour is essentially identical to the single crystals. The compounds [Fe(bppBr)2][BF4]2 (2; bppBr = 4-bromo-2,6-di(pyrazol-1-yl)pyridine) and [Fe(bppI)2] [BF4]2 (3 ; bppI = 4-iodo-2,6-di(pyrazol-1-yl)-pyridine) exhibit more gradual SCO near room temperature, and adopt phase 2 in both spin states. Comparison of 1-3 reveals that the more cooperative spin transition in 1, and its separate crystallographic phase transition, can both be attributed to an intermolecular steric interaction involving the methylsulfanyl substituents. All three compounds exhibit the lightinduced excited-spin-state trapping (LIESST) effect with T(LIESST = 70-80 K), but show complicated LIESST relaxation kinetics involving both weakly cooperative (exponential) and strongly cooperative (sigmoidal) components.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. This is the accepted version of the following article: Cook, LJK, Shepherd, HJ, Comyn, TP, Baldé, C, Cespedes, O, Chastanet, G and Halcrow, MA (2015) Decoupled spin crossover and structural phase transition in a molecular iron(II) complex. Chemistry - A European Journal, 21 (12). 4805 - 4816. ISSN 0947-6539, which has been published in final form at http://dx.doi.org/10.1002/chem.201406307. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | Crystal engineering; Iron; N-ligands; Photomagnetic properties; Spin crossover |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Chemical & Process Engineering (Leeds) > Institute for Materials Research (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 08 Jul 2015 10:13 |
Last Modified: | 12 Mar 2016 23:35 |
Published Version: | http://dx.doi.org/10.1002/chem.201406307 |
Status: | Published |
Publisher: | Wiley-VCH Verlag |
Identification Number: | 10.1002/chem.201406307 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:84883 |