Charge-transfer complexes tetrahydrofurane

Electrochemical studies have shown that Ceo is easily reduced (E1/2 = —0.21 and 0.33 V vs Ag/AgCl in tetrahydrofuran and benzonitrile, respectively [52] and —0.42 V vs SCE in benzonitrile [53, 54]). Up to six electrons can be added reversibly [55]. Several authors have shown that the fullerenes form charge-transfer complexes with amines [33, 56-59]. Wudl et al. have shown that Cgo reacts chemically with amines, giving various substitution products [60, 61]. Since the reduction potential of Ceo should be higher than that of the ground state by the amount of the triplet energy [62,63], its first reduction potential should be near 1.14 V vs SCE in benzonitrile [64]. The triplet should therefore be easily reduced by electron transfer from electron donors of lower oxidation potential. 

Irradiation of an acceptor monomer-electron donor charge transfer complex initiates anionic polymerization in the case of nitroethylene-tetrahydrofuran ( ) and radical polymerization in the case of methyl methacrylate-triphenylphosphine (6). 

Within this class of complexes AH° varies within much broader limits than TAS . The average value of the TAS° terms equals —30.8 kJ/mol. The second subset (points designed by , Fig. 4) consists of charge-transfer complexes, for which AH and TAS were also determined experimentally. (TCNE. .. p-xylene, o-xylene, mesitylene, durene I2. .. dimethylsulfide, diethylsulfide, tetrahydro thiophene TCNE. .. benzene, toluene, naphthalene COfCN). .. furan, thiophene, tetrahydrothiophene, tetrahydrofuran, diethylether, diethylsulfide ). Finally, the third subset (points designed by O, Fig. 4) consist of seven hydrogen-bonded complexes and true vdW molecules for which AH and TAS were evaluated theoretically (cf. Table 8) and... 

The [Ruv(N40)(0)]2+ complex is shown to oxidize a variety of organic substrates such as alcohols, alkenes, THF, and saturated hydrocarbons, which follows a second-order kinetics with rate = MRu(V)][substrate] (142). The oxidation reaction is accompanied by a concomitant reduction of [Ruv(N40)(0)]2+ to [RuIII(N40)(0H2)]2+. The mechanism of C—H bond oxidation by this Ru(V) complex has also been investigated. The C—H bond kinetic isotope effects for the oxidation of cyclohexane, tetrahydrofuran, propan-2-ol, and benzyl alcohol are 5.3 0.6, 6.0 0.7, 5.3 0.5, and 5.9 0.5, respectively. A mechanism involving a linear [Ru=0"H"-R] transition state has been suggested for the oxidation of C—H bonds. Since a linear free-energy relationship between log(rate constant) and the ionization potential of alcohols is observed, facilitation by charge transfer from the C—H bond to the Ru=0 moiety is suggested for the oxidation. 

Charge transfer (CT) complexes, different from aromatic ketone/amine systems, such as quinoline-bromine, pyridine-bromine, tetrahydrofuran-bromine etc. have also been reported to behave as initiators of vinyl polymerization, particularly under photoactivation [65-68]. 

Significant changes in the ligand-to-metal charge-transfer transitions and the f-f transitions in the electronic spectra of (CjHjljYb are observed, when bases like pyrrolidine, triethylphosphine, tetrahydrofuran, or tetrahydrothiophene are added to the complex in benzene solution (Schlesener and Ellis, 1983). The photoluminescence of (C5H5)3Tb and (CH3CjH4)3Tb in tetrahydrofuran solutions have been studied at different temperatures (Brittain et al., 1983). 

By way of contrast, the donor-acceptor complex of tetrahydrofurane and TCNE in solution shows a reversible photoresponse and ESR signal on irradiation in the charge-transfer band. This is attributed to a reversible... 

Poly(vinyl chloride) (PVC) film cast from tetrahydrofuran (THF) probably contains residues in the form of both PVC-THF charge transfer (CT) and PVC-THF-O2 CT complexes [1030,1797]. The formation of a-hydroperoxy-tetrahydrofuran (5.67) is a result of photolysis of the THF-O2 CT complex (cf. section 10.4.6). 

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