1H NMR spectroscopic elucidation in solution of the kinetics and thermodynamics of spin crossover for an exceptionally robust Fe2+ complex

dc.contributor.authorPetzold, Holm
dc.contributor.authorDjomgoue, Paul
dc.contributor.authorHörner, Gerald
dc.contributor.authorSpeck, J. Matthäus
dc.contributor.authorRüffer, Tobias
dc.contributor.authorSchaarschmidt, Dieter
dc.date.accessioned2017-10-24T07:15:20Z
dc.date.available2017-10-24T07:15:20Z
dc.date.issued2016
dc.description.abstractA series of Fe2+ spin crossover (SCO) complexes [Fe(5/6)](2+) employing hexadentate ligands (5/6) with cis/trans-1,2-diamino cyclohexanes (4) as central building blocks were synthesised. The ligands were obtained by reductive amination of 4 with 2,2'-bipyridyl-6-carbaldehyde or 1,10-phenanthroline-2-carbaldehyde 3. The chelating effect and the rigid structure of the ligands 5/6 lead to exceptionally robust Fe2+ and Zn2+ complexes conserving their structure even in coordinating solvents like dmso at high temperatures. Their solution behavior was investigated using variable temperature (VT) H-1 NMR spectroscopy and VT Vis spectroscopy. SCO behavior was found for all Fe2+ complexes in this series centred around and far above room temperature. For the first time we have demonstrated that the thermodynamics as well as kinetics for SCO can be deduced by using VT H-1 NMR spectroscopy. An alternative scheme using a linear correction term C-1 to model chemical shifts for Fe2+ SCO complexes is presented. The rate constant for the SCO of [Fe(rac-trans-5)](2+) obtained by VT H-1 NMR was validated by Laser Flash Photolysis (LFP), with excellent agreement (1/(k(HL) + k(LH)) = 33.7/35.8 ns for NMR/LFP). The solvent dependence of the transition temperature T-1/2 and the solvatochromism of complex [Fe(rac-trans-5)](2+) were ascribed to hydrogen bond formation of the secondary amine to the solvent. Enantiomerically pure complexes can be prepared starting with R,R- or S,S-1,2-diaminocyclohexane( R,R-trans-4 or S, S-trans-4). The high robustness of the complexes reduces a possible ligand scrambling and allows preparation of quasiracemic crystals of [Zn(R, R-5)][Fe(S,S-5)](ClO4)(4)center dot(CH3CN) composed of a 1 : 1 mixture of the Zn and Fe complexes with inverse chirality.en
dc.description.sponsorshipDFG, SFB 658, Elementarprozesse in molekularen Schaltern auf Oberflächenen
dc.identifier.eissn1477-9234
dc.identifier.issn1477-9226
dc.identifier.pmid27506162
dc.identifier.urihttps://depositonce.tu-berlin.de//handle/11303/6897
dc.identifier.urihttp://dx.doi.org/10.14279/depositonce-6236
dc.language.isoen
dc.rights.urihttps://creativecommons.org/licenses/by/3.0/
dc.subject.ddc540 Chemie und zugeordnete Wissenschaftende
dc.title1H NMR spectroscopic elucidation in solution of the kinetics and thermodynamics of spin crossover for an exceptionally robust Fe2+ complexen
dc.typeArticleen
dc.type.versionpublishedVersionen
dcterms.bibliographicCitation.doi10.1039/c6dt01895e
dcterms.bibliographicCitation.issue35
dcterms.bibliographicCitation.journaltitleDalton transactionsen
dcterms.bibliographicCitation.originalpublishernameRoyal Society of Chemistryde
dcterms.bibliographicCitation.originalpublisherplaceCambridgede
dcterms.bibliographicCitation.pageend13809
dcterms.bibliographicCitation.pagestart13798
dcterms.bibliographicCitation.volume45
tub.accessrights.dnbfree
tub.affiliationFak. 2 Mathematik und Naturwissenschaften>Inst. Chemie>FG Bioanorganische Chemiede
tub.affiliation.facultyFak. 2 Mathematik und Naturwissenschaftende
tub.affiliation.groupFG Bioanorganische Chemiede
tub.affiliation.instituteInst. Chemiede
tub.publisher.universityorinstitutionTechnische Universität Berlin
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