Effects of ion aggregation on the intervalence transfer band of the mixed-valence biferrocenium cation in solution

Lowery, Michael D.; Hammack, William S.; Drickamer, H. G.; Hendrickson, David N.

doi:10.1021/ja00260a012

Cited by 35 publications

(33 citation statements)

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“…[6,25,[46][47][48][49][50][51][52][53] The energetic position and exclusive occurrence in the mixed-valent systems Fc 2 C + and (FcEt) 2 C + suggest an IVCT character of these low-energy transitions. In our calculations, however, the charge and spin are fully delocalized and the electronic transitions do not involve any charge transfer between the two units.…”

Section: Discussionmentioning

confidence: 99%

Electronic Structure and Absorption Spectra of Biferrocenyl and Bisfulvalenide Diiron Radical Cations: Detection and Assignment of New Low‐Energy Transitions

Warratz

Aboulfadl

Bally

et al. 2009

Chemistry A European J

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New transitions: Low‐energy electronic transitions have been detected spectroscopically in the FeII–FeIII mixed‐valent biferrocenyl radical cation, but are absent in the spectra of the neutral analogue. They have been assigned by time‐dependent DFT calculations (squares in figure). Analogous investigations were performed for the bisfulvalenide FeII–FeIII radical cation.magnified imageUV‐visible/near‐IR (NIR)/mid‐IR (MIR) solution, solid‐state, and matrix‐isolation electronic absorption spectra of the FeII–FeIII mixed‐valent homobimetallic compounds biferrocenyl triiodide (1) and 1′,1′′′‐diethylbiferrocenyltriiodide (2) reveal the presence of a low‐energy transition in the MIR region that has not been reported before. The new absorption feature and the known NIR band are both assigned to intervalence charge‐transfer (IVCT) transitions. To obtain insight into the electronic structures of 1 and 2, DFT calculations with the BP86 functionals and different basis sets have been performed. Based on the molecular orbital scheme of cation 1, one band corresponds to the transition between the highest occupied d orbitals on the two iron centers, whereas the other one is assigned to a transition from a lower‐lying d orbital to the d orbital. For comparison, the doubly bridged bisfulvalenide diiron cation (3) has been investigated by optical absorption spectroscopy and DFT calculations. The experimental and theoretical results are discussed with respect to the degree of electron localization/delocalization in these systems.

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Section: Discussionmentioning

confidence: 99%

Electronic Structure and Absorption Spectra of Biferrocenyl and Bisfulvalenide Diiron Radical Cations: Detection and Assignment of New Low‐Energy Transitions

Warratz

Aboulfadl

Bally

et al. 2009

Chemistry A European J

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“…It is very likely that similar environmental control features are present for ET in solution. In fact, very recent data [39] on the effect of pressure freezing on the intervalence-transfer (IT) band of mixed-valence complexes have shown that the immediate solvent structure about a complex in solution does not follow the dielectric continuum model. The immediate solvent structure is much more sluggish.…”

Section: Discussionmentioning

confidence: 99%

Electron Transfer in Mixed-Valence Complexes in the Solid State

Hendrickson

1991

Mixed Valency Systems: Applications in Chemistry, Physics and Biology

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ABSTRACT. The factors influencing the rate of intramolecular electron transfer (ET) in the solid state have been investigated for mixed-valence oxo-bridged trinuclear metal acetate complexes and salts of biferrocenium cations. Mixed-valence complexes which have potential-energy barriers for ET and are trapped on the vibrational timescale are studied. These include mixed-valence [M30(02CR)6L3lS, where M is either Fe or Mn, L is a substituted pyridine, and S is a solvate molecule such as C6H6, CHCI3, etc., and salts of the mixed-valence 1 ',1 '''-disubstituted biferrocenium cation. It is shown that it is not the level of intramolecular electronic coupling between metal centers which controls the rate of intramolecular ET. The environment about the mixed-valence complex controls the rate of ET. For salts of mixed-valence 1 ',1 '''-disubstituted biferrocenium cations the positioning of the counteranion relative to the cation controls the rate of ET. If the anion is positioned so that the two iron ions in a cation are inequivalent, the rate of ET is small and the cation is trapped in one valence description. In the case of Fe30 acetate complexes the positioning of the solvate molecule S can lead to valence trapping, even though only van der Waals interactions between the Sand mixed-valence Fe30 complexes exist. Valence detrapping, where the rate of ET increases appreciably, occurs frequently in a phase transition. In the solid-state intermolecular interactions valence trap complexes. As the temperature is increased, the coopenitive onset in a phase transition of motion associated with ligands, counterions, or even solvate molecules leads to valence detrapping. 57Fe Mossbauer, EPR, IR, solid-state 2H NMR and heat capacity data are used to probe these catastrophic events.

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“…[44,45] An additional correction due to comproportionation of the mixed-valence species [75] was not applied since the proportion of the complex in the mixed-valence form (at equilibrium) was > 97.5 %, and the correction does not influence the conclusions reached regarding the relative electronic coupling in the systems investigated. To minimise artefacts in the NIR spectral data due to ion-pairing and concentration effect which are known to influence the IVCT transitions of dinuclear complexes, [36,[76][77][78][79] the spectra were measured using a constant concentration of complex (ca. 1 10 À3 mol dm À3 ) under identical conditions of electrolyte {0.1 mol dm À3 [(n-C 4 H 9 ) 4 N]PF 6 } and temperature.…”

Section: Methodsmentioning

confidence: 99%

Intervalence Charge Transfer (IVCT) in Ruthenium Dinuclear and Trinuclear Assemblies Containing the Bridging Ligand HAT {1,4,5,8,9,12‐hexaazatriphenylene}

D’Alessandro

Keene

2005

Chemistry A European J

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The IVCT characteristics of the mixed-valence forms of the dinuclear [{Ru(bpy)(2)}(2)(mu-hat)](n+) and the trinuclear [{Ru(bpy)(2)}(3)(mu-hat)](n+) species {HAT = 1,4,5,8,9,12-hexaazatriphenylene; bpy = 2,2'-bipyridine} show a marked dependence on the nuclearity, and in the trinuclear case on the extent of oxidation. Small differences are also found between the diastereoisomers of the dinuclear complex {meso (DeltaLambda) and rac (DeltaDelta/LambdaLambda)}, and between the homochiral (Delta(3)/Lambda(3)) and heterochiral (Delta(2)Lambda/Lambda(2)Delta) diastereoisomers of the trinuclear case. The strong metal-metal interactions result in unusual spectroscopic and electrochemical properties of the singly-oxidised (+7) and doubly-oxidised (+8) trinuclear mixed-valence species. A qualitative localised bonding description based on the geometrical properties of the dpi(Ru(II/III)) orbitals is invoked to explain the IVCT behaviour in the di- and trinuclear systems.

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Effects of ion aggregation on the intervalence transfer band of the mixed-valence biferrocenium cation in solution

Cited by 35 publications

References 1 publication

Electronic Structure and Absorption Spectra of Biferrocenyl and Bisfulvalenide Diiron Radical Cations: Detection and Assignment of New Low‐Energy Transitions

Electronic Structure and Absorption Spectra of Biferrocenyl and Bisfulvalenide Diiron Radical Cations: Detection and Assignment of New Low‐Energy Transitions

Electron Transfer in Mixed-Valence Complexes in the Solid State

Intervalence Charge Transfer (IVCT) in Ruthenium Dinuclear and Trinuclear Assemblies Containing the Bridging Ligand HAT {1,4,5,8,9,12‐hexaazatriphenylene}

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