Controlled ligand distortion and its consequences for structure, symmetry, conformation and spin-state preferences of iron(II) complexes

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dc.contributor.authorKroll, Nicole
dc.contributor.authorTheilacker, Kolja
dc.contributor.authorSchoknecht, Marc
dc.contributor.authorBaabe, Dirk
dc.contributor.authorWiedemann, Dennis
dc.contributor.authorKaupp, Martin
dc.contributor.authorGrohmann, Andreas
dc.contributor.authorHörner, Gerald
dc.date.accessioned2016-09-13T12:02:43Z
dc.date.available2016-09-13T12:02:43Z
dc.date.issued2015
dc.description.abstractThe ligand-field strength in metal complexes of polydentate ligands depends critically on how the ligand backbone places the donor atoms in three-dimensional space. Distortions from regular coordination geometries are often observed. In this work, we study the isolated effect of ligand-sphere distortion by means of two structurally related pentadentate ligands of identical donor set, in the solid state (X-ray diffraction, Fe-57-Mossbauer spectroscopy), in solution (NMR spectroscopy, UV/Vis spectroscopy, conductometry), and with quantum-chemical methods. Crystal structures of hexacoordinate iron(II) and nickel(II) complexes derived from the cyclic ligand L-1 (6-methyl-6-(pyridin-2-yl)-1,4-bis(pyridin-2-ylmethyl)-1,4-diazepane) and its open-chain congener L-2 (N-1,N-3,2-trimethyl-2-(pyridine-2-yl)-N-1,N-3-bis(pyridine-2-ylmethyl) propane-1,3-diamine) reveal distinctly different donor set distortions reflecting the differences in ligand topology. Distortion from regular octahedral geometry is minor for complexes of ligand L-2, but becomes significant in the complexes of the cyclic ligand L-1, where trans elongation of Fe-N bonds cannot be compensated by the rigid ligand backbone. This provokes trigonal twisting of the ligand field. This distortion causes the metal ion in complexes of L-1 to experience a significantly weaker ligand field than in the complexes of L-2, which are more regular. The reduced ligand-field strength in complexes of L-1 translates into a marked preference for the electronic high-spin state, the emergence of conformational isomers, and massively enhanced lability with respect to ligand exchange and oxidation of the central ion. Accordingly, oxoiron(IV) species derived from L-1 and L-2 differ in their spectroscopic properties and their chemical reactivity.en
dc.description.sponsorshipDFG, EXC 314, Unifying Concepts in Catalysisen
dc.identifier.eissn1477-9234
dc.identifier.issn1477-9226
dc.identifier.pmid26488906
dc.identifier.urihttps://depositonce.tu-berlin.de/handle/11303/5889
dc.identifier.urihttp://dx.doi.org/10.14279/depositonce-5482
dc.language.isoen
dc.rights.urihttps://creativecommons.org/licenses/by/3.0/
dc.subject.ddc540 Chemie und zugeordnete Wissenschaftende
dc.titleControlled ligand distortion and its consequences for structure, symmetry, conformation and spin-state preferences of iron(II) complexesen
dc.typeArticleen
dc.type.versionpublishedVersionen
dcterms.bibliographicCitation.doi10.1039/c5dt02502h
dcterms.bibliographicCitation.issue44
dcterms.bibliographicCitation.journaltitleDalton transactions : a journal of inorganic chemistry, including bioinorganic, organometallic, and solid-state chemistry / Royal Society of Chemistryen
dcterms.bibliographicCitation.originalpublishernameRoyal Society of Chemistryen
dcterms.bibliographicCitation.originalpublisherplaceCambridgeen
dcterms.bibliographicCitation.pageend19247
dcterms.bibliographicCitation.pagestart19232
dcterms.bibliographicCitation.volume44
tub.accessrights.dnbfree
tub.affiliationVerbundforschung::Exzellenzcluster (EXC)::EXC - UniCatde
tub.affiliationFak. 2 Mathematik und Naturwissenschaften::Inst. Chemie::FG Anorganische Chemie - Festkörper- und Materialchemiede
tub.affiliation.facultyVerbundforschungde
tub.affiliation.facultyFak. 2 Mathematik und Naturwissenschaftende
tub.affiliation.groupEXC - UniCatde
tub.affiliation.groupFG Anorganische Chemie - Festkörper- und Materialchemiede
tub.affiliation.instituteExzellenzcluster (EXC)de
tub.affiliation.instituteInst. Chemiede
tub.publisher.universityorinstitutionTechnische Universität Berlin

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