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Synthesis of 2,6-Di(pyrazol-1-yl)pyrazine derivatives and the spin-state behavior of their iron(II) complexes

hal.structure.identifierSchool of Chemistry [Leeds]
dc.contributor.authorRUFEIDA, Mohammed
hal.structure.identifierInstitut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
dc.contributor.authorCHASTANET, Guillaume
hal.structure.identifierSchool of Chemistry and Photon Science Institute
dc.contributor.authorTUNA, Floriana
hal.structure.identifierSchool of Chemistry [Leeds]
dc.contributor.authorMALKIN TAMSIN, L.
hal.structure.identifierSchool of Chemistry [Leeds]
dc.contributor.authorBARRETT 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.authorLÉTARD, Jean-François
hal.structure.identifierSchool of Chemistry [Leeds]
dc.contributor.authorHALCROW, Malcolm A.
dc.date.issued2013
dc.identifier.issn1434-1948
dc.description.abstractEnChlorination of 2,6-bis(pyrazol-1-yl)pyrazine (bppz) with NaClO in acetic acid afforded 2,6-bis(4-chloropyrazol-1-yl)pyrazine (L2Cl). 2,6-Bis(4-bromopyrazol-1-yl)pyrazine (L2Br), 2,6-bis(4-iodopyrazol-1-yl)pyrazine (L2I), 2,6-bis(4-methylpyrazol-1-yl)pyrazine (L2Me), and 2,6-bis(4-nitropyrazol-1-yl)pyrazine (L2NO2) were also prepared by reactions of the preformed 4-substituted pyrazoles with 2,6-dichloropyrazine. The reduction of L2NO2 with iron powder gave 2,6-bis(4-aminopyrazol-1-yl)pyrazine (L2NH2) and L2I was converted into 2,6-bis[4-(phenylethynyl)pyrazol-1-yl]pyrazine (L2CCPh) by a Sonogashira coupling reaction. The salts [Fe(L2Me)2]X2 (X- = BF4- and ClO4-) underwent thermal spin-crossover abruptly at around 200 K in one and two steps, respectively. The [Fe(L2Me)2]X2 salts exhibited different light-induced excited spin-state trapping (LIESST) behavior; the BF4- salt behaves classically [T(LIESST) = 93 K], but the ClO4- salt undergoes a multistep LIESST relaxation. In contrast, solid [Fe(L2Cl)2][BF4]2 adopts a fixed 2:1 high/low-spin-state population that does not change with temperature below 300 K, whereas [Fe(L2Br)2][BF4]2 and [Fe(L2I)2][BF4]2 form low-spin solvated crystals that are transformed into high-spin powders on drying. The pyrazinyl group in the L2R ligands slightly stabilizes the low-spin state of the complexes, as determined by solution-phase magnetic measurements. The crystal structure of [Fe(L2CCPh)(OH2)z][BF4]2 contains a disordered mixture of six- (z = 3) and seven-coordinate (z = 4) iron centers.
dc.language.isoen
dc.publisherWiley-VCH Verlag
dc.subject.enSpin crossover
dc.subject.enMagnetic properties
dc.subject.enIron
dc.subject.enN ligands
dc.title.enSynthesis of 2,6-Di(pyrazol-1-yl)pyrazine derivatives and the spin-state behavior of their iron(II) complexes
dc.typeArticle de revue
dc.identifier.doi10.1002/ejic.201201100
dc.subject.halChimie/Matériaux
bordeaux.journalEuropean Journal of Inorganic Chemistry
bordeaux.page819-831
bordeaux.issue5-6
bordeaux.peerReviewedoui
hal.identifierhal-00794742
hal.version1
hal.popularnon
hal.audienceInternationale
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-00794742v1
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