Extensive Quinoidal Oligothiophenes with Dicyanomethylene Groups at Terminal Positions as Highly Amphoteric Redox Molecules
摘要:
A series of highly extensive quinoidal oligothiophenes carrying a dicyanomethylene group at both terminal positions is synthesized. As the quinoidal structures extend, they have highly amphoteric abilities and show strong electronic absorptions in the visible to near-infrared region. The higher homologues, quinquethiophene and sexithiophene, exist as equilibrium mixtures with the biradical species.
Synthesis and Spectroscopic Properties of a Series of β-Blocked Long Oligothiophenes up to the 96-mer: Revaluation of Effective Conjugation Length
摘要:
A series of extraordinarily long oligothiophenes up to the 96-mer has been developed by iterative oxidative coupling of the completely beta-blocked sexithiophene. They are highly conjugated like nonsubstituted oligothiophenes, and the effective conjugation of this system is extended to 96 thiophene units and much longer than that previously speculated for polythiophenes.
Conductive, magnetic, and optical properties of sterically hindered dodecithiophenes bearing bulky 2,2-bis(butoxymethyl)-1,3-propanediyl groups were examined. At high doping with FeCl3, a completely hindered dodecithiophene had only a poor conductivity of 5×10−4 S cm−1, but two partially hindered dodecithiophenes had relatively high conductivities of 1.9 and 0.6 S cm−1, which are one or two orders lower than the conductivity (38 S cm−1) of the unhindered dodecithiophene. Despite having different structures and conductivities, all of the doped solids of these dodecithiophenes were magnetically inactive and demonstrated similar optical absorption spectra in the near infrared region, as generally observed for polythiophenes. On the other hand, their optical spectra in dichloromethane were quite different from one another. A solution spectrum of the unhindered dodecithiophene under high doping was characterized by two absorption transitions assignable to a π-dimer. On the other hand, a solution spectrum of the completely hindered dodecithiophene was characterized by an absorption transition due to a bipolaron. Furthermore, the solution spectra of two partially hindered dodecithiophenes could be explained as an overlap of both π-dimeric and bipolaronic bands. From these results, both π-dimer and bipolaron species appear to serve as active charge carriers in conductive poly(oligo)thiophenes.
对带有大体积2,2-双(丁氧基甲基)-1,3-丙二基的立体阻碍十二硫吩的电导率、磁性和光学性质进行了研究。在用FeCl3高掺杂时,完全阻碍的十二硫吩的电导率仅为5×10−4 S cm−1,但两种部分阻碍的十二硫吩的电导率相对较高,分别为1.9和0.6 S cm−1,比未阻碍的十二硫吩的电导率(38 S cm−1)低一到两个数量级。尽管这些十二硫吩的结构和电导率不同,但所有掺杂的固体均不具有磁性,并且在近红外区域显示出类似的光吸收光谱,这与聚噻吩的一般观察结果一致。另一方面,它们在二氯甲烷中的光谱彼此差异很大。高掺杂下未阻碍的十二硫吩的溶液光谱的特征是两个可归因于π-二聚体的吸收跃迁。另一方面,完全阻碍的十二硫吩的溶液光谱的特征是双极子引起的吸收跃迁。此外,两种部分阻碍的十二硫吩的溶液光谱可以解释为π-二聚体和双极子带重叠的结果。从这些结果来看,π-二聚体和双极子似乎都可以作为导电聚(寡)噻吩中的活性电荷载体。
Synthesis and Spectroscopic Properties of a Series of β-Blocked Long Oligothiophenes up to the 96-mer: Revaluation of Effective Conjugation Length
A series of extraordinarily long oligothiophenes up to the 96-mer has been developed by iterative oxidative coupling of the completely beta-blocked sexithiophene. They are highly conjugated like nonsubstituted oligothiophenes, and the effective conjugation of this system is extended to 96 thiophene units and much longer than that previously speculated for polythiophenes.
Extensive Quinoidal Oligothiophenes with Dicyanomethylene Groups at Terminal Positions as Highly Amphoteric Redox Molecules
A series of highly extensive quinoidal oligothiophenes carrying a dicyanomethylene group at both terminal positions is synthesized. As the quinoidal structures extend, they have highly amphoteric abilities and show strong electronic absorptions in the visible to near-infrared region. The higher homologues, quinquethiophene and sexithiophene, exist as equilibrium mixtures with the biradical species.