Dithieno 2,3-b: 3 ,2 -d thiophene

Dibromo-dithieno[2,3-b 3,2 -d]thiophene was also prepared by the author and had a mp = 181-182°C after de-silyation of 4,4 -dibromo-5-trimethylsilane-dithieno[2,3-b 3, 2 ]thiophene. and C-NMR and MS data also provided. 

Three approaches to the synthesis of dithieno[2,3-Z) 3, 2 -J]thiophene (10) and dithieno[3,4-Zr 3, 4 -r thiophene (11) starting from di(bromothienyl) sulfides 8 and 9 were developed (97TL4581, 2000H761). One procedure (condensation a) involves cyclization of sulfides 8 and 9 with hexamethyldistannane catalysed by a palladium complex. Two other procedures involve lithiation, the formation of organocopper (conditions b, c, e) or organozinc (conditions b, d, e) derivatives and their oxidation by molecular oxygen. 

The remaining isomeric dithienothiophenes, poly(dithieno]3,4-b 3, 2 -d]thiophene) (70) and poly(dithieno]3,4-b 2, 3 -d]thiophene) (71), have also been the subject of a number of studies since their initial preparation in 1997 [106]. As with polymer 69, polymers 70 and 71 were prepared by electropolymerization of the corresponding monomeric dithienothiophenes to give films, which undergo both n- and p-doping processes. 

Inaoka and Collard [621] successfully carried out electropolymerization of substituted dithieno[3,4-b 3 ,4 -d]thiophenes, illustrated in Eg. 14.2. finding acceptable conductivities (ca. 5 S/cm with l2-doping) and observing that the 2,5-dioctyl analog was soluble in most organic solvents. 

The first example of a narrow band-gap polymer is polyisothianaphthene [Structure (8)] with a band gap of near 1.0 eV [74,75]. Other polymers designed and synthesized with the intention of developing narrow band-gap polymers include poly(dithieno[3,4-b 3, 4 -d]thiophene [76], poly-4//-cy clopenta[2,1 -6 3,4-/ ]dithiophen-4-one [77], poly-4-dicyanimethy lene-4//-cyclopenta[2,l-6 3,4-6 ]dithiophene [78], poly(2,3-dihexylthieno[3,4-6]-pyrazine (9) [79], polysquaraines [80], polycroconaines [80], poly-(naphtho[2,3-c]thiophene-fl//-bithiophene) (10) [81], a polymer containing... 

A new class of photochromic diarylethenes containing thieno[3,2-b] thiophenes, dithieno[3,2-b 2, 3 -d]thiophene (08CC5203), and dithieno [3,2-fc 2, 3 -d]pyrroles (09CEJ10005) with photoswitchable luminescence properties were synthesized by Suzuki cross-coupling reactions (Scheme 48). 

Scheme 15.4 Structures of narrow-bandgap polythiophene derivatives cyclopenta[2,1-b 3,4-bf Jdithiophene-4-one (CDT) and dithieno[3,4-b 3, 4 -d]thiophene (DTTI)...

Condensation of three thiophene rings, as in dithienothiophenes (5-10), results in a greater reactivity toward oxidizing agents such as peracids, the sulfur atom of the central ring being attacked.121,123,124 Dithieno[3,2-b 2, 3 -d]thiophene (6) and dithieno[3,4-6 3, 4 -[Pg.200]

The synthesis, characterization, electrical conductivity, and field effect mobility of a series of novel soluble N-alkyl dithieno[3,2-b 2, 3 -d]pyrrole (DTP) and thiophene (TH)-based copolymers (DTP-co-THs) were reported (06MM1771 08JA13167). The incorporation of DTP units extends n conjugation, and the introduction of thiophene subunits imparts good solubility, high conductivity, and high charge carrier mobility. Therefore, the incorporation of DTP units and various substituted thiophenes into the polymer backbone affords the ability to enhance the solubility, lower the band gap, and achieve the enhanced electronic properties. 

Fig. 10.24 Structures of polymers absorbing beyond 600 nm (a) poly(dithieno(3,4-b 2, 3 -d)thiophene), (b) tbiophene/isothianaphthalene copolymers, and (c) a thienyl-pyrrole/benzothiazole copolymer.

One of the highest PLQY values, measured in the sohd state for an ohgothiophene-S,S-dioxide was shown by the rigid-core oligomer 3,5-dimethyl-2,3 -bis(3-methylthiophene)-dithieno[3,2-b 2, 3 -d]thiophene-4,4-dioxide, DTTOMe4 ... 

Fig. 7. Molecular structure of 3,5-dimethyl-2,6-bis(dimesitylboryl)-dithieno[3,2-b 2, 3 d]thiophene and PL spectrum in solution (left) and in the solid state (right).

Figure 7.6 Electrical and optical (evaluated by detecting the transmitted light at 490 nm) responses at the 1000th square wave (2 s period) and at the 1010th (8 s) of poly(dithieno 3,2-b 2, 3 -d thiophene), after [21].

M. D. losip, S. Destri, M. Pasini, W. Porzio, K. P. Pemstich and B. Batlogg, New dithieno[3,2-f> 2, 3 -thiophene oligomers as promising materials for organic field-effect transistor applications, Synth. Met., 146, 251-257 (2004). 

FIGURE 17 Structure of selected fused ring systems related to thiophene (a) dithieno(3,2-b 2, y-d) thiophene, (b) dithieno(3,4-/ 3, 4 -d)thiophene, (c) thieno(3,2- )thiophene, and (d) thieno(2,3-6)thiophene. 

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