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Unexpected Spin-Crossover and a Low-Pressure Phase Change in an Iron(II)/Dipyrazolylpyridine Complex Exhibiting a High-Spin Jahn-Teller Distortion.

hal.structure.identifierSchool of Chemistry [Leeds]
dc.contributor.authorKERSHAW COOK, Laurence J.
hal.structure.identifierSchool of Chemistry [Leeds]
dc.contributor.authorTHORP-GREENWOOD, Flora L.
hal.structure.identifierInstitute for Materials Research
dc.contributor.authorCOMYN, Tim P.
hal.structure.identifierSchool of Physics and Astronomy [Leeds]
dc.contributor.authorCESPEDES, Oscar
hal.structure.identifierInstitut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
dc.contributor.authorCHASTANET, Guillaume
hal.structure.identifierSchool of Chemistry [Leeds]
dc.contributor.authorHALCROW, Malcolm A.
dc.date.issued2015
dc.identifier.issn0020-1669
dc.description.abstractEnThe synthesis of 4-methyl-2,6-di(pyrazol-1-yl)pyridine (L) and four salts of [FeL2]X2 (X(-) = BF4(-), 1; X(-) = ClO4(-), 2; X(-) = PF6(-), 3; X(-) = CF3SO3(-), 4) are reported. Powder samples of 1 and 2 both exhibit abrupt, hysteretic spin-state transitions on cooling, with T1/2↓ = 204 and T1/2↑ = 209 K (1), and T1/2↓ = 175 and T1/2↑ = 193 K (2). The 18 K thermal hysteresis loop for 2 is unusually wide for a complex of this type. Single crystal structures of 2 show it to exhibit a Jahn-Teller-distorted six-coordinate geometry in its high-spin state, which would normally inhibit spin-crossover. Bulk samples of 1 and 2 are isostructural by X-ray powder diffraction, and undergo a crystallographic phase change during their spin-transitions. At temperatures below T1/2, exposing both compounds to 10(-5) Torr pressure inside the powder diffractometer causes a reversible transformation back to the high-temperature crystal phase. Consideration of thermodynamic data implies this cannot be accompanied by a low → high spin-state change, however. Both compounds also exhibit the LIESST effect, with 2 exhibiting an unusually high T(LIESST) of 112 K. The salts 3 and 4 are respectively high-spin and low-spin between 3 and 300 K, with crystalline 3 exhibiting a more pronounced version of the same Jahn-Teller distortion.
dc.language.isoen
dc.publisherAmerican Chemical Society
dc.title.enUnexpected Spin-Crossover and a Low-Pressure Phase Change in an Iron(II)/Dipyrazolylpyridine Complex Exhibiting a High-Spin Jahn-Teller Distortion.
dc.typeArticle de revue
dc.identifier.doi10.1021/acs.inorgchem.5b00614
dc.subject.halChimie/Matériaux
bordeaux.journalInorganic Chemistry
bordeaux.page6319-6330
bordeaux.volume54
bordeaux.issue13
bordeaux.peerReviewedoui
hal.identifierhal-01177030
hal.version1
hal.popularnon
hal.audienceInternationale
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-01177030v1
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