Charge transfer compounds

Charge-Transfer Compounds. Similat to iodine and chlorine, bromine can form charge-transfer complexes with organic molecules that can serve as Lewis bases. The frequency of the iatense uv charge-transfer adsorption band is dependent on the ionization potential of the donor solvent molecule. Electronic charge can be transferred from a TT-electron system as ia the case of aromatic compounds or from lone-pairs of electrons as ia ethers and amines. 

Charge-transfer compounds can be isolated ia the crystalline state, although low temperatures are often required. The bromine—dioxane compound, for example, has a chain stmeture (42). 

It is important to recognize that the intermolecular long-distance bonding with the participation of halogen derivatives represents a specific example of the broad general area of donor/acceptor interactions. Moreover, the complexes of molecular iodine, bromine and chlorine with aromatic donors represent classic examples of charge-transfer compounds [26-28] that are vital for the development of Mulliken theory of intermolecular association [29-31]. The latter thus provides the convenient framework for the... 

Azobenzene-linked amphiphile C180AZOSN employed for our experiments (Fig.4.) is an intramolecular charge-transfer compound with donor (alkoxy) and... 

S. Tazuke, R. K. Guo, and T. Ikeda, Time-resolved fluoresence spectroscopy of a twisted intramolecular charge transfer compound bonded to polymers, /. Phys. Chem. 94, 1408(1990). 

Koshihara S, Tokura Y, Iwasa Y, Koda T, Saito G, Mitani T (1991) Domain-wall excitation in organic charge transfer compounds investigated by photo-reflectance spectroscopy. Synth... 

Bousseau L, Valade L, Legros JP, Cassoux P, Garbauskas M, Interrante LV (1986) Highly conducting charge-transfer compounds of tetrathiafulvalene and transition metal- dmit complexes. J Am Chem Soc 108 1908-1916... 

Face-to-face aromatic stacking interactions are common in a wide range of organic charge-transfer compounds where there is a donor-acceptor interaction between an electron rich Ji-system and an electron... 

Fig. 11 The TDAE molecule donates one of its electrons to the C60 molecule producing the TDAE+-Qo charge-transfer compound...

Staab HA (1989) New aspects of organic charge-transfer compounds syntheses, structures and solid-state properties. In Yoshida Z, Shiba T, Oshiro Y (eds) New aspects of organic chemistry I. VCH, Weinheim, pp 227-236... 

It is also remarkable to point out that superconductivity has also been discovered in a family of charge-transfer compounds based on the molecule M(dmit)2, with M = Ni, Pd with Tc -1.6 K under 7 kbar [12] (Fig. 23). In this interesting series, structural and NMR studies support the picture of a one-dimensional Fermi surface, and the ground state competing with superconductivity is a charge density wave modulation driven by the Ni(dmit)2 stacks [85]. 

Although inert-gas clathrates have been described, this compound is believed to be the first xenon charge-transfer compound which is stable at room temperatures. Lattice-energy calculations for the xenon compound, by means of Kapustinskii s equation, give a value 110 kcal. mole", which is only 10 kcal. mole" smaller than that calculated for the dioxygenyl compound. These values indicate that if the compounds are ionic the electron affinity of the platinum hexafluoride must have a minimum value of 170 kcal. mole". ... 

A prototype for such a system is the charge transfer compound tetra-thiafulvalene-tetracyanoquinodimethane (TTF-TCNQ), that contains both anion (TCNQ) and cation (TTF) in the ratio 1 1 [9,10]. The planar molecules of TTF-TCNQ form segregated stacks in a plane to plane manner and the molecular (p-type) orbitals can interact preferentially along the stacking direction. 

First, practically nothing is said of the tremendous development in the so called HTCS, the new oxide superconductors. It could be argued that their metallic conductivity has been known much earlier than that of organic compounds. It is indeed a field by itself, which cannot possibly be dealt with here. It is, in a way, a great pity, as many similarities are observed, for instance between the oxide compounds and the organic charge transfer compounds, as stresses above normal , superconductive or antiferromagnetic properties, quasi low dimensionality, with exacerbated electron-electron interactions when localisation into Id is approached. .. 

The recent discovery (1) and separation (2, 3) of molecular forms of solid carlxin has made possible the formation of new semiconducting 4) and conducting (5) anionic charge-transfer compounds of C o (and C70) with molecular and alkali counterions, respectively. From the latter studies, Hebard et at. (6) have provided unambiguous evidence for superconductivity in solids composed of icosahedral Qo molecules doped with potassium (K,C) with an onset near = 18... 

Intramolecular Charge-Transfer Compound Bonded to Poly (methyl methacrylate)... 

The charge transfer compounds formed when imidazole and benzimidazole are sulfonated by sulfur trioxide have been discussed earlier (see Section 3.02.5.3.3). 

For information about classic charge-transfer compounds, see J. Rose, Molecular Complexes, Pergamon Press, Oxford, 1967. 

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