A-Quaterthiophenes

K. Chondroudis and D.B. Mitzi, Electroluminescence from an organic-inorganic pereovskite incorporating a quaterthiophene dye within lead halide perovskite layer, Chem. Mater., 11 3028-3030,1999. 

Oligothiophene derivatives can also be inserted in a polyester matrix. A quaterthiophene derivative-polyester showed an absorption band at 407 nm and fluorescence emissions at 482 and 507 nm (4>F = 0.17 tf 0.41 ns) (98MM6289). 

In order to continue the study of photoinduced charge separation processes in oligothiophene-based materials, Otsubo et al. recently synthesized two dual oligothiophene-fullerene [Ceol triads 2.132 and 2.133 (Chart 1.26), in which a quaterthiophene and an octithiophene unit were separated by a propyl chain... 

Oligomers based on 4,4-difluorocyclopentadithiophene repeat units exhibit n-type semiconducting behavior [109]. The maximum field effect mobility (0.018 cm V s ) was obtained for a quaterthiophene compound furnished with perfluorohexyl end groups (entry 35, Table 3.1). 

Synthesis of more elaborate oligothiophenes was possible via a sequence of steps first, homocoupling of 2-bromo-3-cyclohexylthiophene took place in the presence of catalytic Pd(PhCN)2Cl2 second, Stille cross-coupling of the resulting dithiophene with 2 equiv of thienyl(tributyl)stannae afforded a quaterthiophene in 76% third, monobromination of the latter product was performed with NBS and finally, dimerization of the heterocyclic C-H bond with Pd(PhCN)2Cl2 provided an olig-othiophene in 53% yield (eq 216). ... 

Several types of nomenclature have been established for the oligothiophenes. Short notations like the original proposed by Bredt [36] (e.g. a,a,a-quaterthio-phene) and later on by Steinkopf [19a] (e.g. a-quaterthiophene) were later followed by the general and more convenient abbreviations nT or a-nT (e.g. 4T or a-4T). However, only the much more complicated systematic nomenclature used by Chemical Abstracts allows the precise denotation of Unkages between rings and positions of substituents. The numbering scheme of thiophene, of the three isomers of bithiophene, and of a substituted terthiophene is given in Fig. 2. 

This method has furthermore been used to synthesize a quaterthiophene regio-isomer. Thus, the reaction of 3,3 -bithiophene 11 with one equivalent of -BuLi affords the 2-lithio compound 17. Coupling of the latter with CUCI2 led in 6%... 

Table 5. Preparation and physical properties of / -substituted a-quaterthiophenes.

Similar results have been obtained with 4T (quaterthiophene) in dichloromethane (absorption maximum at 390 nm). The observed transient spectrum appears structured with two maxima at 560 nm and 610 nm. The lifetime of the corresponding triplet 34T is on the order of 35 (is. The excitation of 6T in dichloromethane (absorption maximum at 432 nm) leads to a transient triplet with an absorption maximum at 680 nm and a lifetime of about 24 (is. 

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