Catalogo Articoli (Spogli Riviste)

OPAC HELP

Titolo:
Electron transfer in a trinuclear oxo-centred mixed-valence iron complex, in solid and solution states
Autore:
Stadler, C; Daub, J; Kohler, J; Saalfrank, RW; Coropceanu, V; Schunemann, V; Ober, C; Trautwein, AX; Parker, SF; Poyraz, M; Inomata, T; Cannon, RD;
Indirizzi:
Univ Regensburg, Inst Organ Chem, D-93053 Regensburg, Germany Univ Regensburg Regensburg Germany D-93053 , D-93053 Regensburg, Germany Univ Erlangen Nurnberg, Inst Organ Chem, D-91054 Erlangen, Germany Univ Erlangen Nurnberg Erlangen Germany D-91054 -91054 Erlangen, Germany Med Univ Lubeck, Inst Phys, D-23538 Lubeck, Germany Med Univ Lubeck Lubeck Germany D-23538 nst Phys, D-23538 Lubeck, Germany Rutherford Appleton Lab, Didcot OX11 0QX, Oxon, England Rutherford Appleton Lab Didcot Oxon England OX11 0QX 1 0QX, Oxon, England Univ E Anglia, Sch Chem Sci, Norwich NR4 7TJ, Norfolk, England Univ E Anglia Norwich Norfolk England NR4 7TJ h NR4 7TJ, Norfolk, England
Titolo Testata:
JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS
fascicolo: 22, , anno: 2001,
pagine: 3373 - 3383
SICI:
1472-7773(2001):22<3373:ETIATO>2.0.ZU;2-J
Fonte:
ISI
Lingua:
ENG
Soggetto:
FATTY-ACID ANIONS; PHASE-TRANSITIONS; VIBRATIONAL-SPECTRA; IRON(III,III,II) CLUSTER; CARBOXYLATE COMPLEXES; NEUTRON-SCATTERING; ACETATE COMPLEXES; METAL-COMPLEXES; TRANSFER RATES; HEAT-CAPACITY;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
92
Recensione:
Indirizzi per estratti:
Indirizzo: Stadler, C CSIC, Inst Catalisis & Petroleoquim, Campus Univ Autonoma, E-28049 Madrid,Spain CSIC Campus Univ Autonoma Madrid Spain E-28049 49 Madrid,Spain
Citazione:
C. Stadler et al., "Electron transfer in a trinuclear oxo-centred mixed-valence iron complex, in solid and solution states", J CHEM S DA, (22), 2001, pp. 3373-3383

Abstract

Complexes [(Fe2MOL3)-M-III-O-II] (M = Fe, Co, Ni, Cu; 2, 3, 4, 5) have been synthesised in which L2- is a pentadentate ligand designed to coordinate all three metal atoms in the central cluster and to inhibit dissociation and solvent exchange processes. Crystal structures for 2, 4 and 5 show threefold symmetry, attributed to rotational disorder. Magnetisation data for 2 indicate strong superexchange between basis oxidation states Fe(3+, 3+, 2+). Comparisons of IR spectra across the series of complexes con rm the non-threefold symmetry of the mixed-valence cluster on the vibrational time scale, both in the solid state and in solution. Proton NMR spectra in solution at room temperature do not distinguish the three iron sites, suggesting thatpseudo-rotation by thermal electron transfer also operates. Cyclic voltammetry and spectroelectrochemical measurements show that the mixed-valence iron complex 2 can be oxidised reversibly to give the tri-iron(III) complex [Fe3OL3](+) and reduced reversibly and quasireversibly to give respectively [Fe3OL3](-) and tri-iron(II) [Fe3OL3](2-), E-0 = 85, -635, -1230 mV (versusFc(+/0)) in dichloromethane (T = 298 K, 0.1 M [n-Bu4N][PF6]). Mossbauer spectra of 2 indicate significant valence delocalisation even at low temperature (4.2 K) with estimated valences Fe(2.9+, 2.9+, 2.2+) in the solid state. At higher temperatures no lifetime broadening is observed but additional Mossbauer absorptions are consistent with increasing proportions of trimer molecules with greater delocalisation, i.e. Fe(2.75+, 2.75+, 2.5+). In frozen solution (THF) the spectra indicate increasing proportions of molecules fully valence-delocalised on the Mossbauer time scale. The data are accounted for with a model which places the complex at the Robin-Day class III/II borderline. It combines strong superexchange with significant double exchange even at the lowest temperatures, while at higher temperatures in solution complete valence delocalisation occurs through intramolecular electron transfer at rates intermediate between the IR and NMR time scales.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 04/04/20 alle ore 02:54:19