Perylene salts

Absorption spectra of more than five-ring systems are compared in Table XII, where only the first and second (and third) bands are listed for simplicity. Pericondensation (195) to 2 shifts the absorption band more bathochromically than catacondensation (30) does. Cyclization of azonia-pentahelicene salt (180) to the corresponding azoniabenzo[g/n ]perylene salt (204) shifts the maximum absorption wavelength about 18 nm longer, similar to the annelation to form azoniahexahelicene salt (206). 

In fact, perylene has been used to produce many cation-radical salts with simple inorganic monoanions (Br, 13 C104", or PF5" and AsF5"), 5 and charge-transfer salts with organic acceptors such as TCNQ and per-fluoroanil. Electrical conductivities at room temperature up to 1400 S.cm have been measured in some cases. On the other hand, perylene salts with magnetic anions such as FeX4 (X" = Cl, Br) and... 

Veiros and M. T. Duarte Perylene Salts with Tetrahalogenoferrate(lll) Anions - Synthesis, Crystal-Structure of [(C2oHi2)3](FeCl4) and Characterization J. Chem. Soc. Dalton Trans. 3543 (1995). 

Other selected examples include tris(tetramethylethylene diamine-sodium)-9,9-dianthryl 143,154 alkali metal salts of 9,10-bis(diisopropylsilyl)anthracene 144,155 as well as the closely related naked 9,10-bis(trimethylsilyl)anthra-cene radical anion 145.156 This chemistry is further extended to the solvent-shared and solvent-separated alkali metal salts of perylene radical anions and dianions 146, 147,156 while other examples focus on alkali metal salts of 1,2-diphenylbenzene and tetraphenylethylene derivatives, where reduction with potassium in diglyme afforded contact molecules with extensive 7r-bonding, [l,2-Ph2C6H4K(diglyme)] 148.157 Extensive 7r-coordination is also observed in (1,1,4,4 tetraphenylbutadiene-2,3-diyl)tetracesiumbis(diglyme)bis(methoxyethanolate) 149.158... 

Although organic anion radicals are oxygen sensitive, they have been isolated as crystalline salts from a variety of electron acceptors (e.g., chloranil, tetracyanoethylene, tetracyanoquinodimethane, perylene, naphthalene, anthracene, tetraphenylethylene, etc.) and their structures have been established by X-ray crystallography.180... 

Unsymmetrically substituted perylene pigments are a comparatively recent novelty. Selective protonation of the tetra sodium salt of perylene tetracarboxylic acid affords the monosodium salt of perylene tetracarboxylic monoanhydride in high yield. Stepwise reaction with amines produces unsymmetrically substituted perylene pigments [2],... 

The dianhydride of perylene tetracarboxylic acid is converted into the pigment form by preparing the corresponding alkali salt and then reprecipitating the compound with an acid. The dianhydride is formed after separating the acid by thermal aftertreatment at 100 to 200°C, possibly under pressure, with an organic solvent. The list of suitable media includes alcohols, ketones, carboxylic acid esters, hydrocarbons, and dipolar aprotic solvents. 

McKenna et al. (1977) found that a bis steroid [10] can bind perylene without micellization. Interestingly, the corresponding monosteroid did not bind perylene in the absence of micellization. The bis-steroid may assume a conformation which is related to the aggregate structure of bile salts. An... 

Perinones are structurally similar to perylenes being made by condensing naphthalene tetracarboxylic dianhydride with amines, but in this case 1,2-diamines, e.g. Cl Pigment Orange 43 (2.71), or its cis isomer. The isomers can be separated by fractionation of their salts. They offer orange to bordeaux shades with similar properties to perylenes, but are less commercially important. 

Intermolecular PET from photoexcited JV-ethyl-2-ethylphenothiazine [87] and perylene [88], for example, to triphenylsulfonium salts produces C—S cleavage to provide diphenylsulfi.de and phenyl radical as well as the cation-radical of the sensitizer. 

The temperature dependence of the NMR relaxation rate Tf1 for the Au compound (Fig. 9) exhibits a typical behavior of one-dimensional conductors with deviations to the Korringa law (Tf1 T) shown by the upward curvature at high temperatures similarly to (TMTTF)2PF6 [41] and TTF[Ni(dmit)2] [42]. Since there are no localized spins on the dithiolate chain, the relaxation comes from the hyperfine contact and dipolar interactions, 7 1 + r j, produced by the spins of the itinerant electrons along the perylene stacks. The enhancement of the relaxation is, however, less important than that shown by the Bechgaard salts [45]. 

Various compounds were shown to sensitize the photochemical decomposition of pyridinium salts. Photolysis of pyridinium salts in the presence of sensitizers such as anthracene, perylene and phenothiazine proceeds by an electron transfer from the excited state sensitizer to the pyridinium salt. Thus, a sensitizer radical cation and pyridinyl radical are formed as shown for the case of anthracene in Scheme 15. The latter rapidly decomposes to give pyridine and an ethoxy radical. Evidence for the proposed mechanism was obtained by observation of the absorption spectra of relevant radical cations upon laser flash photolysis of methylene chloride solutions containing sensitizers and pyridinium salt [64]. Moreover, estimates of the free energy change by the Rehm-Weller equation [65] give highly favorable values for anthracene, perylene, phenothiazine and thioxanthone sensitized systems, whilst benzophenone and acetophenone seemed not to be suitable sensitizers (Table 5). The failure of the polymerization experiments sensitized by benzophenone and acetophenone in the absence of a hydrogen donor is consistent with the proposed electron transfer mechanism. 

The first indication that molecular compounds could exhibit interesting electrical properties apart from those of an insulator was given in 1954, when Akamatu et al. (1) reported a resistivity of p = 10 2 cm for a bromine salt of perylene. Normally perylene crystals themselves are insulating with p = 1014 1016 1 cm therefore, a dramatic change in electronic structure had occurred. The perylene molecule is shown in Fig. 1. 

In the above radical-cation salts, the crystal contains partially oxidized donors, while the electroneutrality is achieved by the presence of closed shell anions. The structural requirements necessary for electrical conductivity in solid salts can also be met upon mixing of donors and acceptors in the resulting charge-transfer (CT) complexes both the donor and acceptor exist in a partially oxidized and reduced state, respectively. Famous examples are the conducting CT complexes formed upon mixing of perylene (112) [323. 324] and iodine or of tetrathiafulvalene (TTF, 119) as donor and 7,7,8,8-tetracyanoquinodimethane (TCNQ, 120) as acceptor [325-327] the crucial structural finding for the... 

Scherer and Willig (65) have studied the rate enhancement, due to cations and protons, of electron transfer from the surface of an organic insulator crystal, such as perylene, to oxidized ions, such as [Fe(CN)g] and fMo(CN)g] ", in solution. In an electrochemical method such as this, the saturation current directly renders the rate constant for electron transfer at the crystal surface. Furthermore, electron transfer on [Fe(CN)6l or [Mo(CN)g] can be studied in the absence of reduced forms, whereas the salt effect can be measured up to the solubility limit. They found that for the same concentration of added electrolyte, rate constants increased with the increased charge of the cation. Up to s 1M rate enhancement was of the order Li < Na < Cs but at salt concentrations >3.5 M a reversal that could be explained by different hydrations of the cations took place. They also found a good linear correlation in the shift to higher redox potentials (simultaneously increasing rate constants) with higher salt concentrations. 

Polycyclic arenes, e.g. perylene, have been widely studied in the preparation of molecular conductors, some of the radical cations show semiconducting or metallic behavior [418]. Introduction of one or more sulfur atoms at the periphery of such systems, i.e. thia arene derivatives, generally imparts greater stability to the radical-cation salts, coupled with increase conductivity [419]. For compound 116, X-ray structure studied have been reported on the pure donor and some radical-ion salts [420]. 

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