Organic Mixed Valence

Hankache, Jihane; Wenger, Oliver S.

doi:10.1021/cr100441k

Cited by 349 publications

(305 citation statements)

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“…This matches nicely with other reported oligophenyl quinone radical anions and is diagnostic of the formation of the semiquinoid radical. 50,51 By powder X-ray diffraction, a small contraction of just 0.9% in the unit cell volume is observed for Mg 2 (dobpdc)(PF 6 ) 0.48 ( Figure 3e and Table S7). As shown in the structure in Figure 1, the long axis of the biphenyl linker runs nearly parallel to the a axis of the unit cell, and the phenoxy−metal bonds lie along neither the a axis nor the c axis.…”

Section: Resultsmentioning

confidence: 99%

A Dual−Ion Battery Cathode via Oxidative Insertion of Anions in a Metal–Organic Framework

2015

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A redox−active metal−organic framework, Fe 2 (dobpdc) (dobpdc 4− = 4,4′-dioxidobiphenyl-3,3′-dicarboxylate), is shown to undergo a topotactic oxidative insertion reaction with a variety of weakly coordinating anions, including BF 4 − and PF 6 − . The reaction results in just a minor lattice contraction, and a broad intervalence charge-transfer band emerges, indicative of charge mobility. Although both metaland ligand-based oxidations can be accessed, only the former were found to be fully reversible and, importantly, proceed stoichiometrically under both chemical and electrochemical conditions. Electrochemical measurements probing the effects of nanoconfinement on the insertion reaction revealed strong anion size and solvent dependences. Significantly, the anion insertion behavior of Fe 2 (dobpdc) enabled its use in the construction of a dual-ion battery prototype incorporating a sodium anode. As a cathode, the material displays a particularly high initial reduction potential and is further stable for at least 50 charge/discharge cycles, exhibiting a maximum specific energy of 316 Wh/ kg.

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Section: Resultsmentioning

confidence: 99%

A Dual−Ion Battery Cathode via Oxidative Insertion of Anions in a Metal–Organic Framework

2015

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“…Since all the iron centers are trivalent as confirmed by Mössbauer spectroscopy, the origin of the IVCT must be the organic dhbq 2−/3− moieties. Interestingly a very sharp absorption edge is observed at low energy (4500 cm −1 ), one of the best-known signatures of Robin-Day Class II/III mixed-valency [193][194][195][196]. This represents the first observation of a Class II/III mixed-valency in a MOF which is also indicative of thermally activated charge transport within the lattice.…”

Section: Anilato-based Multifunctional Organic Framework (Mofs)mentioning

confidence: 63%

Recent Advances on Anilato-Based Molecular Materials with Magnetic and/or Conducting Properties

et al. 2017

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Abstract:The aim of the present work is to highlight the unique role of anilato-ligands, derivatives of the 2,5-dioxy-1,4-benzoquinone framework containing various substituents at the 3 and 6 positions (X = H, Cl, Br, I, CN, etc.), in engineering a great variety of new materials showing peculiar magnetic and/or conducting properties. Homoleptic anilato-based molecular building blocks and related materials will be discussed. Selected examples of such materials, spanning from graphene-related layered magnetic materials to intercalated supramolecular arrays, ferromagnetic 3D monometallic lanthanoid assemblies, multifunctional materials with coexistence of magnetic/conducting properties and/or chirality and multifunctional metal-organic frameworks (MOFs) will be discussed herein. The influence of (i) the electronic nature of the X substituents and (ii) intermolecular interactions i.e., H-Bonding, Halogen-Bonding, π-π stacking and dipolar interactions, on the physical properties of the resulting material will be also highlighted. A combined structural/physical properties analysis will be reported to provide an effective tool for designing novel anilate-based supramolecular architectures showing improved and/or novel physical properties. The role of the molecular approach in this context is pointed out as well, since it enables the chemical design of the molecular building blocks being suitable for self-assembly to form supramolecular structures with the desired interactions and physical properties.Keywords: benzoquinone derivatives; molecular magnetism; multifunctional molecular materials; spin-crossover materials; metal-organic frameworks General IntroductionThe aim of the present work is to highlight the key role of anilates in engineering new materials with new or improved magnetic and/or conducting properties and new technological applications. Only homoleptic anilato-based molecular building blocks and related materials will be discussed. Selected examples of para-/ferri-/ferro-magnetic, spin-crossover and conducting/magnetic multifunctional materials and MOFs based on transition metal complexes of anilato-derivatives, on varying the substituents at the 3,6 positions of the anilato moiety, will be discussed herein, whose structural features or physical properties are peculiar and/or unusual with respect to analogous compounds reported in the literature up to now. Their most appealing technological applications will be also reported.

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“…[36][37]50 Indeed, these absorptions fall into the spectral range in which intervalence absorptions of bis(triarylamine) radical cations are commonly observed. 16,20,[34][35][51][52][53][54][55][56][57][58][59][60][61] An important difference to the intervalence absorptions of coordination compounds 40,[62][63][64][65] are the comparatively large extinction coefficients of these bands, but this is a (favorable) peculiarity of organic mixed-valence compounds which has been noted many times before. Table 2.…”

Section: -49mentioning

confidence: 99%

“…15 Indeed, the oneelectron oxidized or one-electron reduced forms of several oligo-p-phenylene and oligo-p-phenylene vinylene systems could be described well as organic mixed-valence compounds in various experimental studies, [16][17][18][19][20][21][22][23][24][25] but until now there has been comparatively little conceptually analogous work on thiophene systems. [26][27][28][29][30][31][32][33][34][35] A notable exception is the recent study of the oxidized forms of bis (4-(alkoxyphenyl)amino) derivatives of dithienylethene and bithiophene and the finding that a mixed-3 valence description of these cations is meaningful. 36 Another exception is our own recent investigation of photoswitchable organic mixed-valence in dithienylethene systems.…”

Section: Introductionmentioning

confidence: 99%

“…However, it is to be noted that even class II compounds can in principle exhibit EPR spectra that suggest complete delocalization of the unpaired electron spin. 34 Specifically, this is the case in systems in which thermal electron transfer between the two ends of the molecule is rapid on the EPR timescale, i. e., faster than ∼10 -7 s. There have been several comparative investigations of optical and thermal electron transfer in organic mixed-valence systems (mostly on bis(hydrazine) radical cations), [80][81][82] which have come to the conclusion that the results obtained by the two fundamentally different experimental techniques (i. e., optical absorption and EPR spectroscopy) need not necessarily lead to the same conclusion, mostly because these techniques probe electron transfer on significantly different timescales. Be that as it may, in our specific case the EPR data is consistent with the optical absorption results in that both sets of data can be analyzed adequately by assuming complete (in EPR) or nearly complete (in absorption) delocalization of the unpaired electron.…”

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Charge Delocalization in a Homologous Series of α,α′-Bis(dianisylamino)-Substituted Thiophene Monocations

et al. 2012

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A homologous series of three molecules containing thiophene, bithiophene and terthiophene bridges between two redox-active tertiary amino-groups was synthesized and explored. Charge-delocalization in the one-electron oxidized forms of these molecules was investigated by a combination of cyclic voltammetry, near-infrared optical absorption spectroscopy, and EPR spectroscopy. All three cation radicals can be described as organic mixed-valence species, and for all of them the experimental data is consistent with strong delocalization of the unpaired electron. Depending on what model is used for 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 analysis of the optical absorption data, estimates for the electronic coupling matrix element (H AB ) range from ∼5000 cm -1 to ∼7000 cm -1 for the shortest member of the homologous series. According to optical absorption and EPR spectroscopy even the terthiophene radical appears to belong either to Robin-Day class III or to a category of radicals commonly denominated as borderline class II / class III systems. The finding of such a large extent of charge delocalization over up to three adjacent thiophene units is remarkable.

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Organic Mixed Valence

Cited by 349 publications

References 209 publications

A Dual−Ion Battery Cathode via Oxidative Insertion of Anions in a Metal–Organic Framework

A Dual−Ion Battery Cathode via Oxidative Insertion of Anions in a Metal–Organic Framework

Recent Advances on Anilato-Based Molecular Materials with Magnetic and/or Conducting Properties

Charge Delocalization in a Homologous Series of α,α′-Bis(dianisylamino)-Substituted Thiophene Monocations

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