Regiochemistry and Conformation of Poly(3-hexylthiophene) via the Synthesis and the Spectroscopic Characterization of the Model Configurational Triads

Abstract

The four model configurational triads of poly(3-hexylthiophene) (PHT) were synthesized by cross-coupling of the appropriate stannyl and bromo 3-hexylthiophene derivatives, catalyzed by Pd[(C6H6)3P] 4.The comparison of and 13C NMR chemical shifts of the triads with those of PHT allows the unambiguous assignment of the regiochemistry of the polymer. The NMR data of the triads, in conjunction with the results of force field MMP2 calculations, also give information on the conformational properties of PHT samples of different regiochemistry.

The Chemistry of Conducting Polythiophenes

“…Synthesis of the four isomeric trimers by Barbarella and co-workers unambiguously assigned the relative chemical shift of each triad, with each trimer being shielded by about 0.05 ppm relative to the polymer. [63] In (Table 1). These assignments are the same as the assignment by Holdcroft and coworkers [89] and different from those proposed by Sato and Morii.…”

“…[62,63] For the HT-HT example, both methods indicate that the thiophene rings prefer a trans coplanar orientation. Structures with the rings twisted by up to 20 (molecular mechanics) or up to 50 (ab initio-STO-3G) from coplanarity all lie within less than 1 kcal of each other on a very flat potential energy surface and accordingly are easily accessible.…”

The remarkable influence of M 2 δ to thienyl π conjugation in oligothiophenes incorporating MM quadruple bonds

“…The dicarboxylate linker used in the oligomer syntheses is depicted in Scheme 2 Upper. To maximize -conjugation along the thienyl chain, we have maintained the 2,5-substitution pattern at the core C 4 S ring, while n-hexyl substituents are introduced at C(3) and C(4) position to increase solubility (5,(12)(13)(14)(15)(16)(17)(18)(19)(20).The oligomers derived from the dicarboxylate linkers are also compared with the discrete molecular complexes of the type trans-M 2 (TiPB) 2 L 2 (L ϭ thienyl carboxylates) shown in Scheme 2 Lower.A preliminary communication on some relevant aspects of this work was published (11) wherein we noted that the thin films of the oligomers showed electroluminescence when fabricated into an LED device (21,22). We also note that other groups, in particular Wolf and Raithby and their respective coworkers (23-27), have incorporated certain metal ions into oligothiophenes, but their focus was mostly on elements of the later transition metals.…”

“…The dicarboxylate linker used in the oligomer syntheses is depicted in Scheme 2 Upper. To maximize -conjugation along the thienyl chain, we have maintained the 2,5-substitution pattern at the core C 4 S ring, while n-hexyl substituents are introduced at C(3) and C(4) position to increase solubility (5,(12)(13)(14)(15)(16)(17)(18)(19)(20).…”

Synthesis of Donor—Acceptor Substituted Oligothiophenes by Stille Coupling.

“…14,16 Donor-acceptor substituted oligothiophenes represent promising candidates for NLO applications. [1][2][3][4]13,17,20 The synthesis of donor-acceptor oligothiophenes may be achieved by several methods such as cross-coupling reactions; Stille, [14][15][16][17][21][22][23][24] Suzuki, 25 or others 4,6,8,[26][27][28] and by procedures involving thiophene ring formations. 19,[29][30] Recently we have developed an efficient method for the synthesis of 5-amino-and 5-alkoxy-2,2´-bithiophenes.…”