Mixed valence spectrum and cyclic voltammetry of binuclear iron cyano complexes

Glauser, R.; Hauser, Urs; Herren, Fritz; Lüdi, A.; Roder, P.; Schmidt, Eva S.; Siegenthaler, H.; Wenk, F.

doi:10.1021/ja00806a048

Cited by 45 publications

(14 citation statements)

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“…This is a question which can be answered, at least for mixed-valence complexes, by interpreta tion of the oscillator strength of the intervalence band. In Table III, some data (24,25) for the intervalence band of the complex ion [Fe(II)Fe(III)(CN) ] 6~, described initially by Ludi, et al (26), are shown: In this complex, the energy gap 2J separating upper and lower potential surfaces is estimated to be -0.19 eV. This is evi dently too large for the weak-interaction limit to hold.…”

Section: Intervalence Transfermentioning

confidence: 91%

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Parameters of Electron-Transfer Kinetics

Hush

1982

Mechanistic Aspects of Inorganic Reactions

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Over the last two decades, there has been a considerable increase in experimental information about the rates of electron transfer processes, particularly in solution in ionizing solvents. The main features (enthalpies, free energies and entropies of activation) of a large class of these reactions have been broadly understood for about the same length of time. It is interesting to note that the results of very early calculations of outer-sphere reaction rates and their tempera ture dependence frequently agree with recent more detailed estimates. In order to assess the appli cability of different approaches, and thus to discriminate between them, it is desirable to have as much detailed information as possible about the relevant basic parameters. These include, for example, electron coupling or overlap energies, electron-phonon coupling strengths, vibrational frequencies, and spin coupling data. A brief survey is given of the types of experiment which may provide this information. With such data, discussions on matters such as the applicability of Golden Rule perturbation approaches, electronic adiabaticity, the role of nuclear tunnelling, etc., can be put on firmer ground, and some of the outstanding theoretical issues awaiting reso lution are outlined.The theory of homogeneous electron transfer processes, as well as of the closely-related electron exchanges with metallic electrodes, has been the subject of considerable study.The proposal by Hush and by Marcus that these processes are, for simple systems, either usually electronically adiabatic or 0097-6156/82/0198-0301$09.00/0

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Section: Intervalence Transfermentioning

confidence: 91%

“…The value of χ can be also written as Typical values of Γ, (T) so calculated (26) for frequencies in -1 the range 100-400 cm and number of quanta S fe involved in coupling to that mode are shown in Table IV. 13.…”

Section: Nuclear Tunnellingmentioning

confidence: 99%

Parameters of Electron-Transfer Kinetics

Hush

1982

Mechanistic Aspects of Inorganic Reactions

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“…The value of a 2 is comparable to the reported data for dinuclear ion of [(CN) 5 Fe III (NC)-Fe II (CN) 5 ] 6À (a 2 0.03). [14] The small degree of delocalization, which is in contrast to larger delocalizaion in the reported dinuclear complex of [NC-Ru(bpy) 2 -(CN)-Ru(bpy) 2 -CN] 2 (H AB 2000 cm À1 and a 2 0.07), [15] shows the class II behavior. [16] [Fe II 2 Co II 2 (m-CN) 4 (bpy ) Figure 5.…”

Section: Electrochemistrymentioning

confidence: 99%

Cyanide-Bridged Fe−Fe and Fe−Co Molecular Squares: Structures and Electrochemistry of [Fe(μ-CN)4(bpy)8](PF6)4⋅4 H2O, [FeCo(μ-CN)4(bpy)8](PF6)4⋅3 CHCl3⋅2 CH3CN, and [FeCo(μ-CN)4(bpy)8](PF6)6⋅2 CHCl3⋅4 CH3NO2

et al. 2000

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Cyanide-bridged iron-iron and iron--cobalt molecular squares of [Fe(II/4)(mu-CN)4(bpy)8[(PF6)4 x 4H2O (1), [Fe(II/2)Co(II/2)(mu-CN)4(bpy)8](PF6)4 x 3CHCl3 x 2CH3CN (2), and [Fe(II/2)Co(III/2)(mu-CN)4(bpy)8](PF6)6 x 2CHCl3 x 4CH3NO2 (3) (bpy =2,2'-bipyridine) were prepared. X-ray structure analyses for 1-3 were performed and their electrochemistry was studied. In 1-3, four metal ions are bridged by cyanide groups to form tetranuclear macrocycles ("molecular squares"). Each metal ion in the square is six-coordinate: four of the coordination sites are occupied by the nitrogen atoms of two of bpy ligands and the remaining cis coordination sites are occupied by cyanide-carbon or cyanide-nitrogen atoms. In 1, Fe-C (cyanide) (1.899(4)-1.927(4)A) and Fe-N(cyanide) (1.929(4)-1.950(4)A) distances are typical of low-spin Fe2+ ions. In 2, Fe-C(cyanide) and Co(2+)-N(cyanide) bond lengths are in the range 1.919(5)-1.963(5)A and 1.850(5)-2.017(5) A, respectively: in contrast, shorter bond lengths are observed for the metal to cyanide-carbon and cyanide-nitrogen (1.878(7)- 1.893(7) A) in 3. As a result, the molecular squares in 1. 2, and 3 have sides of 4.947(1)4.986(1) A, 5.001(1)-5.053(1) A, and 4.910(1)-4.918(1) A, respectively. Magnetic susceptibility measurements revealed that the Fe2+ and Co3- ions in 1 and 3 are diamagnetic, while the high-spin Co2+ ions in 2 are weakly coupled through the low-spin Fe2 ions. Cyclic voltammograms of the squares are presented, and the electrochemically generated mixed-valent species [Fe(II/2)Fe(III/2)(mu-CN)4(bpy)8]6+ was discussed in terms of the intervalence transfer band.

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“…Scheme 2 shows possible intermediates and reaction pathways for the formation of the Cu 6 Fe 2 cluster (the plots are based on the observed structural parameters). The formation of oligonuclear cyanoferrate(II) species usually involves the reduction of the corresponding iron(III) compounds, [43,44] the reaction of aqua-or aminopentacyanoferrate(II) with hexacyanoferrate(II), or the photochemical labilization of cyanide ligands in [Fe(CN) 6 ] 4Ϫ . [45] Therefore, the host-guest complex 6 was assumed to be stable in solution.…”

Section: Host-guest Complexes Based On the [Cu 3 (L 3 )] 6؉ Cationmentioning

confidence: 99%

Interactions between Copper(II) Complexes of Mono-, Bis-, and Tris(macrocyclic) Ligands and Inorganic or Organic Guests

Comba¹,

Lampeka²,

Nazarenko³

et al. 2002

Eur. J. Inorg. Chem.

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The copper(II)-assisted condensation of [Cu(2,3,2-tet)] 2+ [2,3,2-tet = bis-N,NЈ-(2-aminoethyl)propane-1,3-diamine] with formaldehyde and melamine (melamine = 2,4,6-triamino-1,3,5-triazine) afforded melamine-based mono-, bis-, and tris(macrocyclic) ligand/copper(II) complexes in approx. 30% overall yield. Three different monocopper(II), one dicopper(II), and one tricopper(II) complex structures are reported, as well as two structures of host-guest assemblies of the tricopper(II) complex with benzene-1,3,5-tricarboxylate and one resulting from a reaction with hexacyanoferrate(II) to afford an octanuclear Cu 6 Fe 2 complex. These structures are discussed together with those of five previously reported

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Mixed valence spectrum and cyclic voltammetry of binuclear iron cyano complexes

Cited by 45 publications

References 1 publication

Parameters of Electron-Transfer Kinetics

Parameters of Electron-Transfer Kinetics

Cyanide-Bridged Fe−Fe and Fe−Co Molecular Squares: Structures and Electrochemistry of [Fe(μ-CN)4(bpy)8](PF6)4⋅4 H2O, [FeCo(μ-CN)4(bpy)8](PF6)4⋅3 CHCl3⋅2 CH3CN, and [FeCo(μ-CN)4(bpy)8](PF6)6⋅2 CHCl3⋅4 CH3NO2

Interactions between Copper(II) Complexes of Mono-, Bis-, and Tris(macrocyclic) Ligands and Inorganic or Organic Guests

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