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Thermal and light-induced spin-transitions in iron(II) complexes of 2,6-bis(4-halopyrazolyl)pyridines: the influence of polymorphism on a spin-crossover compound

hal.structure.identifierSchool of Chemistry [Leeds]
dc.contributor.authorPRITCHARD, Ruth
hal.structure.identifierInstitut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
dc.contributor.authorLAZAR, Hanane Z.
hal.structure.identifierSchool of Chemistry [Leeds]
dc.contributor.authorBARRET, Simon A.
hal.structure.identifierSchool of Chemistry [Leeds]
dc.contributor.authorKILNER, Colin A.
hal.structure.identifierInstitut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
dc.contributor.authorASTHANA, Saket
hal.structure.identifierInstitut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
dc.contributor.authorCARBONERA, Chiara
hal.structure.identifierInstitut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
dc.contributor.authorLETARD, Jean-François
hal.structure.identifierSchool of Chemistry [Leeds]
dc.contributor.authorHALCROW, Malcolm A.
dc.date.issued2009
dc.identifier.issn1477-9226
dc.description.abstractEnThe syntheses of 2,6-bis(4-chloropyrazol-1-yl)pyridine (L1), 2,6-bis(4-bromopyrazol-1-yl)pyridine (L2) and 2,6-bis(4-iodopyrazol-1-yl)pyridine (L3) by electrophilic halogenation of 2,6-bis(pyrazol-1-yl)pyridine are reported. The complex [Fe(L1)2][BF4]2 crystallises in two different solvent-free polymorphs. The tetragonal (alpha) form crystallises in a known version of the "terpyridine embrace" structure, and undergoes an abrupt spin-transition at 202 K. The orthorhombic (beta) form exhibits a modified form of the same packing motif, containing two unique iron sites in a 2 : 1 ratio. One-third of the complex molecules in that material undergo a very gradual thermal spin-crossover centred at 137 K. Comparison of the two structures implies that spin-crossover cooperativity in the alpha-polymorph is transmitted in two dimensions within the extended lattice. [Fe(L2)2][BF4]2 is isostructural with alpha-[Fe(L1)2][BF4]2 and exhibits a similarly abrupt spin-transition at 253 K. In contrast, [Fe(L3)2][BF4]2 is low-spin as a powder at 360 K and below and can be crystallised as two different solvates from acetone solution. All three compounds exhibit the LIESST effect at 10 K, with photoconversions of 40-100%. Their LIESST relaxation temperatures obey the empirical T(LIESST) = T0- 0.3T(1/2) (T0 = 150 K) law that we have previously proposed for this class of compound.
dc.language.isoen
dc.publisherRoyal Society of Chemistry
dc.title.enThermal and light-induced spin-transitions in iron(II) complexes of 2,6-bis(4-halopyrazolyl)pyridines: the influence of polymorphism on a spin-crossover compound
dc.typeArticle de revue
dc.identifier.doi10.1039/b907094j
dc.subject.halChimie/Matériaux
bordeaux.journalDalton Transactions
bordeaux.page6656-6666
bordeaux.issue33
bordeaux.peerReviewedoui
hal.identifierhal-00430160
hal.version1
hal.popularnon
hal.audienceInternationale
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-00430160v1
bordeaux.COinSctx_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rft.jtitle=Dalton%20Transactions&rft.date=2009&rft.issue=33&rft.spage=6656-6666&rft.epage=6656-6666&rft.eissn=1477-9226&rft.issn=1477-9226&rft.au=PRITCHARD,%20Ruth&LAZAR,%20Hanane%20Z.&BARRET,%20Simon%20A.&KILNER,%20Colin%20A.&ASTHANA,%20Saket&rft.genre=article


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