Thiophenes charge transfer

Several patents describe solid-state lithium batteries with the iodine-thiophen charge-transfer complex. " ... 

Scheme 4 Proposed stacking structure. The plane-to-plane distance d for the polymer shown in No. 19 is about 3.8 A [93-95], which is somewhat shorter than the d value (about 3.85 A) reported for head-to-tail-type poly(3-alkylthiophene) HT-P3RTh [128,129] and somewhat longer than the d values (3.6-3.65 A) observed with head-to-head-type poly(4-alkylthiazole-2,5-diyl) [124,129,130] and the charge-transfer-type copolymer of thiophene and 4-alkylthi-azole [131]. Poly(ethylenedioxythiophene) gives a similar d value (3.8 A) [132]. The existence of S in the aromatic ring seems to make the distance d longer...

The term charge tranter refers to a succession of interactions between two molecules, ranging from very weak donor-acceptor dipolar interactions to interactions that result in the formation of an ion pair, depending on the extent of electron delocalization. Charge transfer (CT) complexes are formed between electron-rich donor molecules and electron-deficient acceptors. Typically, donor molecules are p-electron-rich heterocycles (e.g., furan, pyrrole, thiophene), aromatics with electron-donating substiments, or compounds... 

Various applications of 13C NMR spectroscopy have been made examples include analysis of the spectra of substituted thieno[2,3-6 ]thiophenes (76ACS(B)417> and studies of the relaxation of both proton and 13C nuclei (80JMR(40)197>. The 13C spectra of thiophenium salts have been examined and, again, a strong downfield shift of the 0 -carbon atoms is seen, indicative of considerable charge transfer from sulfur to the 0 -positions (74TL75). 

Two situations are conducive to ipso attack. If polar effects come into play in stabilizing the transition state of the addition of the radical, then frequently ipso attack is encountered. This is clearly brought out in the different behaviour of adamantyl and methyl radicals towards the same substrate. It has been firmly established that while methyl and phenyl radicals are electroneutral, the bridgehead adamantyl radical behaves as a nucleophilic species (80ACR51). If this adamantyl radical is reacted with thiophene substrates made electron deficient by the presence of suitable substituents, then the transition state of the addition step may have the character of a charge-transfer complex the site at which the... 

Photolysis of allyl iodide in thiophene gives a mixture of 2-allyl- (63.8%) and 3-allyl-(36.2%) thiophenes (77JOC1570). This is in contrast to homolytic phenylation, where almost exclusive 2-phenylation takes place (Section 3.14.2.9). It has been suggested that the rate-determining step in the allyl substitution reaction has a small but definite charge-transfer character. 

Most of the information presently available has been obtained with a view to comparing selenophene and tellurophene with furan and thiophene, and has already been discussed in Chapter 3.01. The resulting ionization potentials are in good agreement with those deduced from the spectra of charge transfer complexes with tetracyanoethylene (82CS(20)214, 75JCS(F1)2045). 

An example of transfer of electron from nucleophile to substrate is seen in the formation of the radical anions (observable by ESR) of 5-halo-2A/,3W-benzotf>]thiophene-2,3-diones on treatment with nucleophiles.20 It has been proposed in some cases, that this single-electron transfer step takes place through a charge transfer complex between the nucleophile and the aromatic substrate.21-22 Some reactions occur spontaneously, i.e. without any catalysts or reagents other than the substrate and the nucleophile, but the initiation process is usually, although not invariably, photostimulated (near-ultraviolet radiation, 300-... 

Oligomers with 11 thiophene units showed an absorption maximum at 462 nm (91JA5887). The terthiophene derivative 21 and some other oli-gothiophene derivatives were studied because the coexistence of an electron-rich moiety (the terthiophene spine) and electron-deficient moiety (the dicyanomethylene groups on either side of the molecule) is expected to cause intramolecular charge-transfer (89BCJ1539 95BCJ2363 ... 

An investigation with the electron donor 4-methoxybenzo[b]thiophene (35) and electron acceptor p-chloroacetophenone (36) and with the bichro-mophores 37 and 38, where the above donor and acceptor moieties are connected by an olefinic (unsaturated as well as saturated) spacer, was performed (02JPP(A)(152)41). The absorption spectra of the donor 35 in the presence of the electron acceptor 36 were measured in n-heptane and highly polar acetonitrile solutions. In both nonpolar and highly polar media, it was found that the spectra of the mixture of 35 and 36 are just the superposition of the absorption bands of the individual components. This observation excludes the possibility of formation of any ground state charge transfer (CT) complex. 

After irradiation, a silver-colored thin polymer layer totally covers the liquid phase. During the irradiation process, the color of the liquid phase has changed from yellow to a deep red one. The red color is due to a charge transfer complex between iodine and the thiophene ring dissolved in the liquid. The polymerization process takes place only at the surface of the irradiated sample. However, it was observed that when the UV-irradiation by excimer laser is over, the polymerization process continues, but only at the surface of the irradiated sample a postpolymerization without incident UV-photons takes place. It was also observed that the presence of oxygen during... 

The above method was used for preparation of a new class of cofacially oriented neutral donor-acceptor thienothiophenes, namely 3-(4-methoxyphenyl)-4-(3-pyri-dyl) thicnol2,3-/ ]thiophene 199 and its ionic analog 200 (Scheme 37). The synthesis of 199 and 200 has been described to probe the presence of through-space charge transfer interactions [49],... 

These theoretical results discussed in the preceding paragraph are fully consistent with the experimental XPS and UPS data. Indeed, the new features appearing on the C(ls), S(2p), and Al(2p) XPS spectra constitute dear evidence of the charge transfer from aluminum to carbon and sulphur. Other model configurations, where the aluminum atoms are made to interact either only with the sulphur atoms or only with the 0-carbon atoms, are calculated to be much less stable than the Al—C structure described above, and do not result in any electron density redistribution consistent with the XPS results. The inert character of the 0-carbons, and of the adjacent thiophene units, upon reaction of aluminum with a given thiophene unit also is reflected in the spectra, as the major part of the C(ls) and S(2p) contribution remains unshifted when aluminum is deposited... 

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