Bithiophenes interactions

Dipolar cycloaddition of 2,4-(trimethylsilyl)- and 2,4-(trimethylgermyl)-substituted thiophene-1,1-dioxides as well as silylated 2,2 -bithiophene-1,1-dioxides was investigated. It was shown that only the C(4)=C(5) double bond of 2,4-disubstituted thiophene-1,1-dioxides interacts with acetonitrile oxide to give thienoisoxazoline dioxides. Bithiophene derivatives were inactive or their reaction with nitrile oxide was accompanied by desilylation. Cycloaddition of benzonitrile oxide with all mentioned sulfones did not occur. The molecular structure of 3a-methyl-5.6a-bis(trimethylgermyl)-3a,6a-dihydrothieno 2.3-c/ isoxazole 4,4-dioxide was established by X-ray diffraction (263). ... 

The interaction of 2,4-dichlorothiophene (6) with 3,5-dichloro-2H-thiophenium ion (5) to give bithiophene 7 is an electrophilic substitution in which cation 5 is an electrophile. Similarly, the add-induced oligomerization of five-membered heteroaromatics is a resinification. The structure of 3,4-dimethylpyrrole dimer formed in 6N HCl (68JCS(C) 2526) shows that the oligomerization may proceed (Scheme 11) through a 2H-pyrrolium ion, reaction 2 in Scheme 2. 

In polymers snch as poly(di-octyl-fluorene-co-bithiophene) (E8T2) in which close interchain interactions are weakened by the sp -coordinated carbon atom on... 

M. Baibarac, I. Baltog, and S. Lefrant, Raman spectroscopic evidence for interfacial interactions in poly(bithiophene)/single-walled carbon nanotube composites. Carbon, 47, 1389-1398 (2009). 

We have recently shown that 3,6-dimethoxythieno[3,2-h]thiophene 21 leads to a polymer presenting low oxidation potential and moderate bandgap (1.7 eV) [74]. The advantage of thienothiophene unit compared to bithiophene one resides in the planar structure and absence of positional isomers. Furthermore, the crystallographic structure of the dimer 22 (Figure 13.1), shows a hilly planar conjugated system stabilized by noncovalent intramolecular sulhir-oxygen interactions. 

Another strategy proposed by Sannicolo et al. consists of the use of cyclopentabithiophene precursors with either a 16-crown-5-ether ring coplanar to the bithiophene moiety (74) or a 15-crown-5-ether perpendicular to it (75) [180]. This approach considerably reduces the steric interactions between the complexing site and the conjugated backbone. Consequently, the precursors were readily electropolymerized into extensively conjugated polymers as confirmed by optical data. The analysis of electrochemical properties in the presence of alkali cations showed that while poly(75) is completely insensitive to change of the cationic species, the redox potential of poly(74) undergoes a 350 mV positive shift in the presence of Na" " [ 180]. 

Swager and coworkers synthesized receptor polymers 102 and 103 [209,210]. The polymers were prepared by copolymerization of 2,5-dibromo-3-decylthiophene or 3,3 -bis(methoxyethoxy)-2,2 -bithiophene with the organozinc derivative of the macrocyclic 3,3 -dialkoxy-2,2 -bithiophene by palladium-catalyzed cross-coupling. Cyclic voltammetry and in situ conductivity measurements on polymer films have evidenced the complexation of paraquat derivatives. However, the complexation between polymer films and acceptors can lead to opposite shifts of oxidation potential of the polymer due to the interplay of donor-acceptor interaction and conformational changes of the polymer. 

Sannicolo et al. first reported the electropolymerization of a Ceo-derivatized bridged bithiophenic precursor (235) [431]. Ferraris et al. have described the synthesis and the electropolymerization of a bithiophene with a Cgo group attached at P-position by an alkyl spacer (236), whereas processable PT copolymers were postfunctionalized with Cgo to give polymers [432]. Recently, PT with Cgo groups connected to the rr-conjugated polymer chain by a phenyl polyether linker has been prepared by electropolymerization of bithiophene 237 [427,433]. While the donor backbone and the acceptor moiety do not interact in the ground state, a photoinduced electron transfer between the PT chain and the attached Cgo group has been demonstrated by ESR measurements. 

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