Charge-transfer crystals

Kochi and co-workers engineered heteromolecular charge-transfer crystals of a tricyclic dithiin 34 stacked alternately with anthracene, which can undergo spontaneous Diels-Alder cycloaddition to give a novel artificial crystal system <2001JA87, 2001JA4951>. 

Iwasa Y, Koda T, Koshihara S, Tokura Y, Iwasawa N, Saito G (1989) Intrinsic negative-resistance effect in mixed-stack charge-transfer crystals. Phys Rev B39 10441-10444... 

Collet E, Lemee-Cailleau MH, Buron-Le Cointe M, Cailleau H, Wulff M, Luty T, Koshihara S, Meyer M, Toupet L, Rabiller P, Techert S (2003) Laser-induced ferroelectric structural order in an organic charge-transfer crystal. Science 300 612-615... 

Haarer D (1980) Optical and photoelectric properties of organic charge transfer crystals. Festkor-Adv Solid St 20 341... 

The charge-transfer crystal of 1,4-dithiin and anthracene was grown in dichloro-methane solution (50 mM) by slow evaporation of solvent at low temperature (-4 °C). After one week, a brown single crystal was isolated. The solid-state reaction of the anthracene-1,4-dithiin CT crystals was carried out at four temperatures (viz. 50, 60, 70 and 80 °C), and the conversion was monitered by XH NMR spectroscopy. 

The Mulliken arguments may be extended to charge-transfer crystals. The first solid charge-transfer crystals studied were colored, but had low thermodynamic stability relative to the separate neutral donor and acceptor crystals. However, if the donor D had low ID and if the acceptor had high Aa ... 

Infrared and Raman spectroscopy of organic charge-transfer crystals... 

Table 4.22. Optical spectral (one-electron) transition energies ( ) calculated for manganese oxides using the MS-SCF-ATa method, compared with experimentally observed transitions assigned to charge transfer, crystal field, valence band conduction band and crystal field conduction band transitions...

Begley, M. J., Crombie, L Griffiths, G. L. and Tone, R. C. F. (1981). Charge-transfer and non-charge-transfer crystal forms of (E)-(5,5 -dimesitylbifuranylidenediones and X-ray stractural investigation. J. Chem. Soc., Chem. Commun., 823-5. [216] Beilstein Institute (1978). How to use Beilstein. Beilstein handbook of organic chemistry. Beilstein Institute, Frankfurt. 

Owing to the special principles of topochemical reactions polydiacetylene copolymers can only be obtained if the comonomers form mixed crystals. Apart from this obvious preparative aspect mixed crystals are of interest because it can be expected that the monomer reactivity and the polymer properties can be effectively varied by the crystal composition. Similar effects have been successfully demonstrated in the isostructural doping of organic charge-transfer crystals In addition, it can be... 

Figure 3. ORTEP diagrams of donor-acceptor pairs in charge-transfer crystals of (A) ferrocene and 6w(durene)iron(II) [124], (B) durene and i u(hexamethylbenzene) iron(II) [124], and (C) tricyano-methide and 6M(hexamethylbenzene)iron(II) [120],...

Figure 6. Transient (diffuse-reflectance) absorption spectrum (—) obtained at 25 ps following the 532-nm laser excitation of charge-transfer crystals of [CpFeCpCH2N+Mc3]2 M06O19 dispersed in neutral alumina (10 %). The spectrum is deconvoluted as the (1 1) sum of reduced hexamolybdate...

Complete back electron transfer upon charge-transfer excitation has also been observed in crystalline EDA complexes. For example, laser excitation of the charge-transfer crystals of ferrocenyl donor and polyoxomolybdate acceptor results in short-lived (ps) transients the diffuse-reflectance absorption spectrum of which is shown in Figure 6 [137]. This transient spectrum can be deconvoluted as the sum of the absorption spectra of the oxidized ferrocenyl donor (ferrocenium) and the re-... 

Table 2 summarizes [391 the electrical conductivity of several charge-transfer crystals, most of which have a definite Peierls transition to a semiconducting state below a temperature T. In some cases, however, there is instead a very broad maximum in the conductivity vs. temperature plot, and the compound retains its high conductivity to the lowest temperatures measured, without ever going superconducting. One such salt, Cu(DMDCNQI)2, even reaches ct = 5x 10 S cm at 0.5 K. 

Mohwald, H., Erdle, E., and Thaer, A. Orientational phase transition in a charge-transfer crystal triplet excitons as probes for lattice dynamics. Chemical Physics 27, 79-87 (1978). 

When the intermolecular forces are relatively strong and directional, crystalline molecular compounds (crystalline molecular complexes) are formed. They have fixed stoichiometries and ordered structures. These two-component molecular crystals are also called cocrystals or maybe adduct crystals. Hydrogen-bonded cocrystals, donor-acceptor crystals (charge transfer crystals), and inclusion crystals (host-guest crystals) are examples of crystalline molecular complexes. Crystalline organic salt is a special case of hydrogen-bonded cocrystal or donor-acceptor crystal, i.e., proton (or electron) transfer from the acid (or donor) to base (or acceptor) occurred. 

Electrical and magnetic properties of donor-acceptor crystals (charge transfer crystals) are interesting in view of their potential applications to organic conduc-... 

A -Alkylcarbazoles formed yellow to orange to deep brown 1 1 charge transfer crystals with wi-dinitrobenzene, 3,5-dinitrobenzoic acid (3,5-DNBA) and its derivatives (Scheme 30) [57]. On the other hand, attempts to obtain adduct crystals of A -alkylcarbazoles with o- or p-dinltrobenzene and with 2,4- or 3,4-dinitrobenzoic acid failed. Upon solid-state photolysis, many of these adduct crystals underwent photoredox reactions and e a position of the A -alkylcarba-zoles was oxidized to produce carbazole, JV-acylcarbazoles, and A/-(hydroxy-... 

The intense theoretical and experimental activity in the organic charge transfer crystals exemplified by TTF-TCNQ has led to several intriguing new results in the past year. In particular, the observation of the Kohn anomaly and Peierls instability in both x-ray and neutron... 

The main object of this lecture is to emphasize the importance of asymmetry in creating attractive interactions between the delocalized electrons of biopolymers and charge transfer crystals and to prove the reality of our former results obtained for DNA models by presenting theoretical results obtained for the experimentally carefully investigated TCNQ complexes. 

Very highly conducting charge-transfer compounds based on 7,7,8,8-tetra-cyanoquinodimethane (TCNQ) continue to attract much attention. Some of the recent work has been summarized by Holmes-Siedle.82 The theory of -molecular charge-transfer crystals, of which the TCNQ salts form the most important category, has been thoroughly reviewed.83... 

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