Ferrocene charge-transfer complexes

Metallicenium cations and ferrocene charge transfer complexes The ferricenimn cation may be isolated with anions such as Is [77,93] BF4 [93] and FeCU" [94,95]. The ferricenium ion has one unpaired electron but it shows no electron spin resonance since the ground state is orbitally degenerate [95a, 80]. It has been suggested that the ferricenium ion forms complexes in solution with the anions Is , FeCU [96a] and carboxylates [956]. However, the Mdssbauer spectrum of solid ferricenium tetrachloroferrate suggests it to be the salt [(7r-C5H5)2Fe]+FeCl4 [94]. Further, potentiometric studies show that there is no appreciable complex formation between the ferricenium and chloride ions in water at 25 [96a]. 

The structures of the black crystalline benzene solvate C6o-4C6H6, the black charge-transfer complex with bis(ethylenedithio)tetrathiafulvene, [C6o(BEDT-TTF)2], and the black ferrocene adduct [C6o Fe(Cp)2)2] (Fig. 8.7b) ) have also been solved and all feature the packing of Cso clusters. 

Over the past decade a number of new covalently bonded TTF/ferrocene adducts have been reported [77, 78]. The crystal structure of the l,l -bis(l,3-dithiole-2-ylidine)-substituted ferrocene derivative has been published [77]. In this complex, ferrocene has essentially been incorporated as a molecular spacer between the two l,3-dithole-2-ylidene rings forming a stretched TTF molecule. This adduct, and its methyl-substituted derivative, have been combined with TCNQ to form charge-transfer complexes with room temperature powder conductivities of 0.2 S cm-1. Similar diferrocenyl complexes have been prepared with bis (dithiolene) metal complexes [79, 80]. 

A stable ferrocene-TCNE adduct has been prepared and its structure, closely analogous to charge-transfer complexes of benzenoid systems has been determined to be that shown as 4.20 Whether a charge-transfer species involving the iron atom rather than the ring is possible has not been deter-... 

In addition to ferrocene, the oxidative redox couple that has received the most attention in supramolecular chemistry is tetrathiofulvalene (TTF), 35. This compound undergoes two reversible one-electron oxidations, first to a radical cation and then to a dication (Eq. 1.21). TTF first came to prominence in the 1970s when it was discovered that the charge transfer complex between it and 7,7,8,8-tetracyanoquinonedimethane (TCNQ) shows metallic conductivity. As a result, a large variety of different TTF derivatives have been prepared and characterized. This rich synthetic chemistry, coupled with the electroactivity, has intrigued supramolecular chemists for some time, with the result that the TTF unit has been incorporated into a wide variety of... 

Spectroscopic methods can be used to specify the position of donors and acceptors before photoexcitation [50]. This spatial arrangement can obviously influence the equilibrium eomplexation in charge transfer complexes, and hence, the optical transitions accessible to such species [51]. This ordered environment also allows for effective separation of a sensitizing dye from the location of subsequent chemical reactions [52], For example, the efficiency of cis-trans isomerization of A -methyl-4-(p-styryl)pyridinium halides via electron transfer sensitization by Ru(bpy) + was markedly enhanced in the presence of anionic surfactants (about 100-fold) [53], The authors postulate the operation of an electron-relay chain on the anionic surface for the sensitization of ions attached electrostatically. High adsorptivity of the salt on the anionic micelle could also be adduced from salt effects [53, 54]. The micellar order also influenced the attainable electron transfer rates for intramolecular and intermolecular reactions of analogous molecules (pyrene-viologen and pyrene-ferrocene) solubilized within a cationic micelle because the difference in location of the solubilized substances affects the effective distance separating the units [55]. 

A. Charge-Transfer Complexes of Bis(arene)iron(II) and Ferrocene ... 

The structure of the charge-transfer complex can be solved in the tetragonal space group P42/nmc, with a = 11.200(3) A and c = 13.283(5) A, as a discrete 1 1 mixture of individual ferrocene and bis(durene)iron(II) hexafluorophosphate units, that is,... 

It can be assumed that AICI3 combines with the ring of highest electron density, rather than with the iron atom of ferrocene. This decreases the stability of the metal-ring bond, and stimulates further substitution in this ring. There are some data indicating that in charge-transfer complexes in... 

Ferrocene-Containing Charge-Transfer Complexes. Conducting and Magnetic Materials... 

Charge-Transfer Complexes of Poly-alkylated Ferrocenes... 

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