Electronic structure of linear thiophenolate-bridged heterotrinuclear complexes [LFeMFeL]n(+) (M = Cr, Co, Fe; n = 1-3): Localized vs delocalized models
Glaser, Thorsten
Beissel, T
Bill, E
Weyhermuller, T
Schunemann, V
Meyer-Klaucke, W
Trautwein, AX
Wieghardt, K
The reaction of mononuclear [LFe<SUP>III</SUP>] where L represents the trianionic ligand 1,4,7-tris(4-tert-butyl-2-mercaptobenzyl)-1,4,7-triazacyclononane with CrSO<INF>4</INF>. 5H<INF>2</INF>O, CoCl<INF>2</INF>. 6H<INF>2</INF>O, or Fe(BF<INF>4</INF>)<INF>2</INF>. 6H<INF>2</INF>O and subsequent oxidation with ferrocenium hexafluorophosphate or NO(BF4) or reduction with [(tmcn)Mo(CO)<INF>3</INF>] (tmcn = 1,4,7-trimethyl-1,4,7-triazacyclononane) produced an isostructural series of [LFeMFeL]<SUP>n+</SUP> complexes, the following salts of which were isolated as crystalline solids: (i) [LFeCrFeL](PF<INF>6</INF>)<INF>n</INF> with n = 1 (1a), n = 2 (1b), and n = 3 (1c); (ii) [LFeCoFeL]X<INF>n</INF> with X = BPh<INF>4</INF> and n = 2 (2b) and X = PF<INF>6</INF> and n = 3 (2c); (iii) [LFeFeFeL](BPh<INF>4</INF>)<INF>n</INF> with n = 2 (3b) and n = 3 (3c). All compounds contain Linear trinuclear cations (face-sharing octahedral) with an N<INF>3</INF>Fe(mu-SR)<INF>3</INF>M(mu-SR)<INF>3</INF>FeN<INF>3</INF> core structure. The electron structure of all complexes has been studied by Fe and M K-edge X-ray absorption near edge structure (XANES), UV-vis, and EPR spectroscopy, variable-temperature, variable-field susceptibility measurements, and Mossbauer spectroscopy (in zero and applied field). The following electronic structures have been established: (1a) Fe<SUP>II</SUP>(ls)Cr<SUP>III</SUP>Fe<SUP>II</SUP>(ls) (ls = low-spin) with a spin ground state of S<INF>t</INF> = 3/2; (1c) Fe<SUP>III</SUP>(ls)Cr<SUP>III</SUP>Fe<SUP>III</SUP>(ls) with an S<INF>t</INF> = 1/2 ground state; (2c) Fe<SUP>III</SUP>(ls)Co<SUP>III</SUP>(ls)Fe<SUP>III</SUP>(ls) with an S<INF>t</INF> = 1 ground state; (3c) Fe<SUP>III</SUP>(ls)Fe<SUP>III</SUP>(ls)Fe<SUP>III</SUP>(ls) with an S<INF>t</INF> = 1/2 ground state. For 1b (S<INF>t</INF> = 2) it is found that the two iron ions are spectroscopically equivalent (Fe<SUP>2.5</SUP>) and, therefore, the excess electron is delocalized (class III): [LFe<SUP>2.5</SUP>Cr<SUP>III</SUP>Fe<SUP>2.5</SUP>L]<SUP>2+</SUP>. For 2b clearly two different iron sites prevail at low temperatures (4.2 K); at higher temperatures (>200 K) they become equivalent on the Mossbauer time scale. Thus, 2b is class II with temperature-dependent electron hopping between the Fe<SUP>II</SUP> and Fe<SUP>III</SUP> ions. 3b is again fully delocalized (class III) with an S<INF>t</INF><SUP></SUP> = 1 ground state; the excess electron is delocalized over all three iron sites. The electronic structure of all complexes is discussed in terms of double exchange and superexchange mechanisms.
American Chemical Society (ACS)
1999
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doc-type:article
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https://pub.uni-bielefeld.de/record/2398092
Glaser T, Beissel T, Bill E, et al. Electronic structure of linear thiophenolate-bridged heterotrinuclear complexes [LFeMFeL]n(+) (M = Cr, Co, Fe; n = 1-3): Localized vs delocalized models. <em>Journal of the American Chemical Society</em>. 1999;121(10):2193-2208.
eng
info:eu-repo/semantics/altIdentifier/doi/10.1021/ja982898m
info:eu-repo/semantics/altIdentifier/issn/0002-7863
info:eu-repo/semantics/altIdentifier/issn/1520-5126
info:eu-repo/semantics/altIdentifier/wos/000079242800023
info:eu-repo/semantics/closedAccess