Valence Detrapping Research Articles

Inter-Metallocene Cross-Coupling Reaction and Oxidation Study on Hetero Nuclear Bimetallocene Compounds including Fe, Ru and Os

Abstract Hetero nuclear bimetallocene compounds, ferrocenylruthenocene (FcRc), ferrocenylosmocene (FcOc), ruthenocenylosmocene (RcOc) and 1-ferrocenyl-4-ruthencoenylbenzene (FcPhRc) were synthesized by Suzuki–Miyaura coupling or Negishi coupling reaction. When these compounds were oxidized with I2, mixed-valence compounds, [(C5H5)FeII(C5H4-C5H4)OsIV-I(C5H5)]I3 (1), [(C5H5)RuII(C5H4-C5H4)OsIV-I(C5H5)]I3 (3) and [(C5H5)FeIII(C5H4-Ph-C5H4)RuIV-I(C5H5)](I3)2 (4), were obtained. The valence state was investigated by using 57Fe Mössbauer spectroscopy and variable-temperature 1H NMR spectroscopy. FcOc was also oxidized by [(C5H5)2RuIV-Cl]PF6, and the ferrocenylosmocenium-Cl adduct [(C5H5)FeII(C5H4-C5H4)OsIV-Cl(C5H5)]PF6 (2) was obtained. The valence detrapping described as FeII-OsIV$ \rightleftharpoons $ FeIII-OsIII was observed by 1H NMR measurement in high-temperature solution. The valence detrapping was also observed in solid state by 57Fe Mössbauer spectroscopy.

Mössbauer spectroscopic study on valence-detrapping and trapping of mixed-valence trinuclear iron(III, III, II) fluorine-substituted benzoate complexes

Four mixed-valence trinuclear iron(III, III, II) fluorine-substituted benzoate complexes were synthesized; Fe3O(C6F5COO)6(C5H5N)3·CH2Cl2 (1), Fe3O(C6F5COO)6(C5H5N)3 (2), Fe3O(2H-C6F4COO)6(C5H5N)3 (3), and Fe3O(4H-C6F4COO)6(C5H5N)3 (4), in which valence-detrapping and trapping phenomena have been investigated by 57Fe- Mossbauer spectroscopy. The valence state of the three iron ions is trapped at lower temperatures while it is fully detrapped at higher temperatures for 1. Valence detrapping is not observed for 2, 3, and 4 even at room temperature, although Mossbauer spectra for 3 and 4 show complicated temperature dependence.

Electronic coupling in a highly preorganized bimetallic complex comprising pyrazolate-bridged CpMn(CO)2 moieties.

By means of a multistep synthetic procedure a dimanganese complex has been prepared, in which a N,N'-bridging pyrazolate ligand spans two CpMn(CO)(2) subunits in a highly preorganized chelate arrangement. The Xray crystallographic analyses of the Mn(I)Mn(I) complex K(+)1(-) and of its non-chelate precursor complex elucidate details of the molecular structure, in particular an unusual pyrazolate binding mode in the solid state and intertwining of the CO ligands in the crowded bimetallic array 1(-). The Mn(I)Mn(I) compound (1(-)), the mixed-valent Mn(I)Mn(II) (1), and the oxidized Mn(II)Mn(II) form (1(+)) have been characterized by various analytical and spectrosopic methods, such as electrochemistry, variable-temperature EPR spectroscopy, IR spectroelectrochemistry, and UV/Vis/NIR spectroelectrochemistry as well as by DFT and TD-DFT calculations. Strong electronic coupling in the mixed-valent complex is observed, but time- (and temperature-) dependent valence detrapping occurs, thus placing 1 in class II according to the Robin and Day assignment, close to the class II/III transition. From variable-temperature EPR spectroscopy a rough estimate of the activation energy and rate for thermal electron transfer can be deduced, with E(th) ( not equal )=13.6 kJ mol(-1) and k(th)=2.6 x 10(10) s(-1) at 298 K. Unexpectedly, no intervalence CT transition for 1 is detected in solution, but one appears in the optical spectrum of solid 1. The conclusions drawn from experiments are fully supported by DFT calculations that were carried out for all three forms of the dimanganese complex. A broken symmetry treatment for mixed-valent 1 reveals almost perfect localization of both spin and charge on one Mn center. According to TD-DFT the first excited states of 1 give rise to the IT processes in the NIR-energy region, as observed in the solid-state spectrum. The HOMOs are located at the Mn ions and are favorably arranged for pi interactions with the bridging pyrazolate.

Control of the symmetry of binuclear ferrocene derivative by using chiral substituent and its mixed-valence state

The mixed-valence 1′,1′′′-bis(( R)-2-phenylbutyl)-, 1′,1′′′-bis(( S)-2-phenylbutyl)- and 1′-(( R)-2-phenylbutyl)-1′′′-(( S)-2-phenylbutyl)-1,1′′-biferrocenium salts were investigated to reveal the importance of cation symmetry on the mixed-valence states. ( R, R) and ( S, S) samples never showed the perfect valence detrapping, while ( R, S) sample showed the detrapped-valence state at room temperature.

The role of a terminal benzene ring on the mixed-valence state of a series of 1′,1‴-bis( n-phenylalkyl)-1,1″-biferrocenium triiodides

The relation between the mixed-valence state of the central Fe atoms and the crystal structure is discussed in a series of 1′,1‴-bis( n-phenylalkyl)-1,1″-biferrocenium triiodides ( n=2, 3, 4, 6). The mixed-valence states depend strongly on the methylene substituent in these salts. The 2-phenylethyl and 4-phenylbutyl derivatives show valence detrapping with increasing temperature, although their quadrupole splitting values are considerably different from each other at lower temperatures. On the other hand, the 6-phenylhexyl derivative shows the temperature-independent trapped-valence state. The initiation temperature of valence detrapping in 4-phenylbutyl derivative is lowered by changing the recrystallizing solvent from hexane to dichloromethane, accompanied by a change in the powder X-ray diffraction pattern. The temperature dependences of the quadrupole splitting values in the salts under investigation can be explained using constant quadrupole splitting values both for typical ferrocene- and ferrocenium-like doublets and only by changing the energy difference between the Fe II–Fe III and Fe III–Fe II states in the solid state. Both the cation and anion in the 2-phenylethyl derivative are located on the center of symmetry, which is in good agreement with the 57Fe Mössbauer spectrum results at room temperature. By comparison of the present results with those of the corresponding dialkyl derivatives, the important role of the terminal benzene ring in the mixed-valence state is clarified. The role is based on intermolecular interaction via the benzene ring.

Intermediate mixed-valence state between the valence-trapped and valence-detrapped states in 1′,1‴-bis(3-phenylpropyl)-1,1″-biferrocenium triiodide

57Fe Mössbauer spectroscopy and X-ray crystallography reveal that 1′,1‴-bis(3-phenylpropyl)-1,1″-biferrocenium triiodide shows an intermediate mixed-valence state between the typical temperature-independent trapped-valence state and typical `fusion type' valence detrapping.

Even−Odd Character and Dynamic Electronic State in the Binuclear Ferrocene Derivatives with Long Alkyl Substituents

X-ray powder diffraction patterns revealed that 1‘,1‘‘‘-diheptyl- and 1‘,1‘‘‘-dioctyl-1,1‘‘-biferrocenium triiodides obtained from hexane and from dichloromethane have a layered structure with longer interlayer distances. 1‘,1‘‘‘-Diheptyl-1,1‘‘-biferrocenium triiodide falls under the category reported before, while 1‘,1‘‘‘-dioctyl-1,1‘‘-biferrocenium triiodide becomes exception; it shows a valence detrapping with increasing temperature despite the longer interlayer series. The difference in the crystal structure between longer and shorter interlayer distance series was reflected in the difference of the space group. 1‘,1‘‘‘-Diheptyl-1,1‘‘-biferrocenium triiodide (C34H46Fe2I3) crystallizes in the monoclinic space group P21/c with unit cell parameters a = 27.209(10) Å, b = 9.6480(6) Å, c = 14.042(10) Å, β = 98.572(4)°, and Z = 4, while 1‘,1‘‘‘-dioctyl-1,1‘‘-biferrocenium triiodide (C36H50Fe2I3) crystallizes in the monoclinic space group P21/c with a = 20.758(6) Å, b = 9.80(1) Å, c = 37.88(2) Å, β = 90.44(3)°, and Z = 8. Both salts in the present study have a space group of P21/c, which is different from the shorter interlayer series; 1‘,1‘‘‘-dihexyl- and 1‘,1‘‘‘-didodecyl-1,1‘‘-biferrocenium triiodides have a space group of P1̄. The difference in the structure between the 1‘,1‘‘‘-diheptyl derivative and the 1‘,1‘‘‘-dioctyl derivative is also discussed. There is a difference in the symmetry of the monocation between the two salts, while both show the unsymmetrical triiodide anion. The difference between them makes the difference of the cation−cation interaction. The structure of the cations agrees with the result of 57Fe Mössbauer spectroscopy. The cation−cation interaction in the stacking is observed in 1‘,1‘‘‘-dioctyl derivative, while such interaction is disturbed by the adjacent stacking in 1‘,1‘‘‘-diheptyl derivative.

Electron Transfer in Mixed-Valence [Fe(III)(2)Fe(II)O(O(2)CCH(3))(6)(3-Cl-py)(3)].3-Cl-py: Effects of a Crystallographic Phase Transition and Conversion of Solvate and Ligand Molecules from Statically Disordered to Dynamically Disordered on the Valence Detrapping.

A crystallographic phase transition involving changes in the solvate molecule has been found for mixed-valence [Fe(3)O(O(2)CCH(3))(6)(3-Cl-py)(3)].3-Cl-py (1), where 3-Cl-py is 3-chloropyridine. Single-crystal X-ray structures were determined at 300, 228, 200, 169, and 122 K for complex 1. At 300, 228, and 200 K the crystal is monoclinic, space group P2(1)/c, whereas at 169 and 122 K it is triclinic, space group P&onemacr;. Determinations of the unit cell parameters at several temperatures shows that a reversible crystallographic phase transition between the monoclinic and triclinic forms occurs at approximately 200 K. Complex 1 crystallizes in the monoclinic space group P2(1)/c at 300 K, having a unit cell with a = 21.212(8) Å, b = 8.434(2) Å, c = 23.676(3) Å, and Z = 4. Refinement with 5702 observed [F(o) > 4sigma(F(o))] reflections gave R = 0.0542 and R(w) = 0.0937. Complex 1 crystallizes in the triclinic space group P&onemacr; at 122 K, having a unit cell with a = 20.983(11) Å, b = 8.360(4) Å, c = 23.293(10) Å, and Z = 4. At 300 K there is one somewhat asymmetric Fe(3)O complex in the structure. The core dimensions in the Fe(3)O complex at 300 K indicate that the complex is becoming almost valence-detrapped. At 122 K there are two different Fe(3)O complexes in the unit cell, both of which are similar in dimensions. As the temperature is decreased from 300 to 122 K, each Fe(3)O complex becomes more and more distorted in an equilateral triangle. At 122 K one iron ion in each Fe(3)O complex clearly is a high-spin Fe(II) ion and the other two are high-spin Fe(III) ions. There are significant changes in the nature of the 3-Cl-py solvate molecules above and below the phase transition that are likely important in controlling the valence detrapping. At 122 K there are two different Fe(3)O complexes, each with their nearby 3-Cl-py solvate molecules in one position. There are three different phases: a monoclinic one with all solvate molecules disordered, a second triclinic phase at 169 K with half of the solvate molecules disordered, and a third triclinic phase at 122 K with all solvate molecules statically ordered. (57)Fe Mössbauer spectra taken in the 110-293 K range show that complex 1 converts from valence-trapped at 110 K to become detrapped by 293 K, where a single quadrupole-split doublet is seen. Throughout the 140-230 K range it was necessary to employ one Fe(III) doublet and two Fe(II) doublets to fit each Mössbauer spectrum. It is shown that the two Fe(II) doublets likely arise from Fe(3)O complexes experiencing the different disordered solvate environments described above. Thus, while the approximately 200 K structural phase transition involving the solvate molecules does not precipitously lead to an increase in the rate of electron transfer in Fe(3)O complexes in 1, it is clear that the changes seen in the solvate molecules from X-ray structures do play a major role in the valence detrapping in complex 1.

Phase Transition in 1′, 1′″-Dihexylbiferrocenium Triiodide Accompanied by a Change In Mixed-Valence State

Abstract Two different crystals of 1′, 1′″-dihexylbiferrocenium triiodide were obtained from the different solution (hexane or dichloromethane). The salt prepared from hexane has a longer interlayer distance and gives trapped-valence state of Fe atoms, while the salt recrystallized from dichloromethane has a shorter interlayer distance and gives typical fusion-type valence detrapping of the mixed- valence state on the 57Fe Mössbauer spectroscopy. By annealed at 323 K the latter changes into the former salt. The X-ray diffraction study of the latter supports the results of the 57Fe Mössbauer spectroscopy.

Dependence of the rate of intramolecular electron transfer on crystal form in mixed-valence trinuclear iron phenylacetate complex

A dependence of the rate of intramolecular electron transfer on crystal form in mixed-valence trinuclear iron phenylacetate, [Fe 2 IIIFe IIO(O 2CCH 2Ph) 6(py) 3](py=pyridine), was found. This complex was obtained in two different crystal forms: a columnar and a needle crystal form. Mo¨ssbauer spectra of the columnar crystals showed a temperature-dependent valence detrapping, whereas the needle crystals showed a trapped mixed-valence state from a lower temperature up to room temperature. The structure of the columnar crystal was determined by single-crystal X-ray diffraction. The complex is located on the C 2 axis passing through central O Fe; thus, there are two crystallography inequivalent iron sites. The Fe Fe distances are 3.305(1) and 3.311(1)A˚, in agreement with their being indistinguishable on the 57Fe Mo¨ssbauer time-scale (∼10 −7–10 −8s). There is no evidence indicating intermolecular π-π interactions through the phenyl groups and/or pyridine ligands.

Structural consequences of electron-transfer reactions. 26. Evidence for time-dependent valence detrapping in a mixed-valent dimanganese fulvalenyl cation

Structural consequences of electron-transfer reactions. 26. Evidence for time-dependent valence detrapping in a mixed-valent dimanganese fulvalenyl cation

Valence detrapping in mixed-valence biferrocenes: evidence for phase transitions

The preparation and physical data characterizing valence detrapping for the PF 6 - and SbF 6 - salts of the mixed-valence dichlorobiferrocenium, 1',1'''-dihromohiferrocenium, and 1', 1'''-diiodohiferrocenium cations are presented. All six compounds are shown to he valence trapped on the vibrational time scale as indicated by C-H bending bands seen in the 815-85-cm -1 region of the IR spectrum

Mixed-valence biferrocenes: pronounced anion dependence of valence detrapping and effects of an asymmetric crystal lattice

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMixed-valence biferrocenes: pronounced anion dependence of valence detrapping and effects of an asymmetric crystal latticeRobert J. Webb, Steven J. Geib, Donna L. Staley, Arnold L. Rheingold, and David N. HendricksonCite this: J. Am. Chem. Soc. 1990, 112, 13, 5031–5042Publication Date (Print):June 1, 1990Publication History Published online1 May 2002Published inissue 1 June 1990https://doi.org/10.1021/ja00169a006RIGHTS & PERMISSIONSArticle Views113Altmetric-Citations51LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

ChemInform Abstract: Pronounced Anion Dependence of Valence Detrapping Temperature in Mixed‐Valence 1′,1′′′‐Disubstituted Biferrocenium Salts.

AbstractChanging from I3‐ to PF6‐ for the counter ion in (Ia) leads to a change from valence detrapped at 4.2 K to valence trapped at 350 K on the Moessbauer time scale.

Pronounced Anion Dependence of Valence Detrapping Temperature in Mixed‐Valence 1′, 1‴‐Disubstituted Biferrocenium Salts

Pronounced Anion Dependence of Valence Detrapping Temperature in Mixed‐Valence 1′, 1‴‐Disubstituted Biferrocenium Salts

Highly cooperative valence detrapping of mixed-valence manganese complex [Mn3O(O2CCH3)6(py)3](py) in the solid state

Highly cooperative valence detrapping of mixed-valence manganese complex [Mn3O(O2CCH3)6(py)3](py) in the solid state

Valence detrapping in iron(II)-iron(III) models of iron-oxo proteins

Valence detrapping in iron(II)-iron(III) models of iron-oxo proteins

ChemInform Abstract: Heat Capacity and Phase Transition of the Mixed‐Valence Compound Biferrocenium Triiodide

The results of the measurement of heat capacity at constant pressure, C,,, of the mixed-valence compound biferrocenium triiodide with an adiabatic calorimeter between 14 and 360 K are reported. This compound is known to show a trapped-valence state at low temperature on the 57Fe Mossbauer time scale and a detrapped average valence state at high temperatures. Heat capacity data are presented to show that biferrocenium triiodide exhibits a phase transition in the same temperature region where the valence detrapping occurs on the S7Fe Mossbauer time scale. The present calorimetric measurements indicate a main C, peak centered at 328 K and two subsidiary small peaks at 312 and 346 K. These three peaks may be attributed to the phase transition arising from different sample histories (mainly different grain sizes of the specimen). The phase transitions are characterized by weak cooperativity; the excess heat capacity due to the phase transition is observed over a wide temperature region from -220 to -360 K. The transition entropy was found to be ASm = (1.77 & 0.06) J K-' mol-'. This value is unexpectedly small even if one takes into account only the contribution from the onset of intramolecular electron transfer in the binuclear cations, which amounts to R In 2 (=5.76 J K-' mol-'), where R is the gas constant. Based on the temperature acquisition of AS,,,, the average of the potential energy difference between two electron-localized states, ( FeAFeB') and ( FeArrrFeB), was estimated. The result indicates incompleteness of the phase transitions. A qualitative microscopic model for the phase transition is presented. Intermolecular interactions in the stacks of mixed-valence cations are suggested to be important. In order to have a phase transition it is also important to have interactions between a given cation and its neighboring 1,- anions. In order to examine the role of the 13- counteranion, far-infrared and Raman spectra have been recorded in the range below 400 cm-' as a function of temperature. The symmetric stretching mode (ul) of the I,- anion was observed at 110 cm-I in the Raman spectrum while the deformation (u2) and asymmetric stretching (u,) modes were observed at 55 and 136 cm-' in the IR spectrum. The observation of such a mutual exclusion of vibrational modes between the IR and Raman experiments suggests that the I,- anion in biferrocenium triiodide has nearly a linear symmetrical form, and thus a charge oscillation between two distorted forms I--I-I and I-I--I- does not occur in the range 101-340 K. At the very least the distortion of the 1,- anion in biferrocenium triiodide is not as appreciable as it is in other statically distorted cases. IR and Raman data are also presented for the analogous mixed-valence compound 1',6'-dichlorobiferrocenium triicdide hemiicdine. In keeping with the X-ray structural results, which show an asymmetric It- anion in this compound, all three I,- vibrational modes are seen both in the IR and Raman spectra.