Polythiophenes arylations

Kraft et al., 1998 Lowen and Van Dyke, 1990 Wei and Tian, 1993], Reactions other than oxidative polymerization are also being studied for producing polyaniline and polythiophene [Kraft et al., 1998 Loewe et al., 2001]. An example is the Pd-catalyzed dehydrohalogenation between aryl dihalides and aryl primary diamines to synthesize polyanilines [Kanbara et al.,... 

The use of the heteroaryl Heck reactions extends beyond fine chemicals synthesis. Polythiophenes were prepared starting from 3-octyl-2-iodotiophene by heating in the presence of palladium acetate and tetrabutylammonium chloride (6.91.),122 The arylation of benzothiophene has also been achieved under the same conditions.123... 

Whereas in solution the photoluminescence efficiency (Of) of poly(3-alkylthiophenes) (PATs) is 3(Mf)%, it drastically drops to 1-4% and lower in the solid state due to the increased contribution of nonradiative decay via interchain interactions and ISC caused by the heavy-atom effect of sulfur (97MM4608). Optoelectronic devices of this type of compounds have been studied (98SCI(280)1741 06SM(156)1241). Fibers of poly(3-hex-ylthiophene) for photovoltaic applications have been described (07MI1377). Poly(3-octylthiophene) showed a TTA band at 800 nm (96JPC15309). The photophysical properties of some alkyl and aryl polythiophenes have been studied (03JCP(118)1550). The absorption maximum of poly(3-octylthiophene) is at 438 nm, while the fluorescence was... 

The reaction of sulfur-containing heterocyclic compounds such as thiophenes and thiazoles (Eq. 68) is specifically enhanced by addition of Cul, while the role is not yet definitive [135]. The use of a bulky phosphine ligand such as P(f-Bu)3 also promotes the arylation [141]. 2-Iodothiophenes are polymerized to produce polythiophenes (Eq. 69) [142]. 

Synthesis of aryl coupled thiophenes and polymerization of these by conventional procedures leads to new copolymers which have different properties compared to the parent polythiophenes. This oligomeric approach towards building novel copolymers has been used to modify the main-chain and also to incorporate fractional amounts of functionalities in the side chains of the polymer back-bone. 

Another unique modification of the aryl spacer is the preparation of (155) <90JA5662, 92MI 212-I6, 93JA1869>. This orthogonal arrangement of polythiophene units produces a conducting polymer that can act as a molecular switch <88JA5687>. 

Functionalization of polythiophenes with aryl groups has attracted much interest because aryl terminals can be further functionalized. A series of 3-phenyl- and 4-phenylthiophene substituted on the phenyl ring with donor or acceptor groups has been electropolymerized [208] in order to tune the potentials for p and n doping. Monomer oxidation potential and polymer redox potentials were found to follow a linear Hammett correlation. 

Migita-Kosugi-Stille, Negishi-Baba, Mizoroki-Heck, and Kumada-Tamao-Corriu coupling) and for polythiophene synthesis. Direct arylation (see Chapter 4) was highlighted as one of the more efficacious methods. 

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