物理化学学报 >> 1994, Vol. 10 >> Issue (09): 825-829.doi: 10.3866/PKU.WHXB19940911

研究论文 上一篇    下一篇

聚噻吩取代效应的理论研究

周传华, 李奇, 黄元河, 刘若庄   

  1. 北京师范大学化学系,北京 100875
  • 收稿日期:1993-09-14 修回日期:1994-03-17 发布日期:1994-09-15
  • 通讯作者: 刘若庄

A Theoretical Study on the Substituent Effect of Polythiophene

Zhou Chuan-Hua, Li Qi, Huang  Yuan-He, Liu Ruo-Zhuang   

  1. Department of Chemistry,Beijing Normal University,Beijing 100875
  • Received:1993-09-14 Revised:1994-03-17 Published:1994-09-15
  • Contact: Liu Ruo-Zhuang

摘要:

用自洽场晶体轨道法(SCF CNDO/2-CO)对聚噻吩的一些一取代物和二取代物的电子结构进行了研究,计算的取代基包括-CH3,-C2H5,-OCH3和-CN.计算结果表明,这些取代基基本没有影响聚噻吩主链的平面结构,除聚-3,4-二甲基噻吩的主链发生了40°的扭转外,其它衍生物的主链仍处于同一平面. 根据各取代高分子的电子特性我们得到结论:给电子基团和吸电子基团的取代都将使能隙(Eg)减小,价带宽和导带宽都较聚噻吩有所减小. 给电子基团的取代将使高聚物的电离能和电子亲合势减小,更有利于p-型氧化掺杂.吸电子基因的取代将使电离能和电子亲合势都增大,更有利于n-型掺杂.文章对各种取代高聚物的晶体轨道进行了深入的分析和讨论.

关键词: 聚噻吩衍生物, 取代基效应, 自治场晶体轨道法, 电子结构

Abstract:

We present a theoretical investigation of the electronic structure of some derivatives of poly-thiophene (PT), mainly poly (3-methylthiophene) (PMT), poly (3-ethylthiophene) (PET), poly(3-methoxythiophene) (PMOT), poly(3-cyanothiophene)(PCNT), poly (3,4-dimethyl thiophene) (PDMT), poly (3,4-dimethoxy thiophene)(PDMOT), poly (3,4-dicyanothiophene) (PDCNT), poly (3-methoxy-4-methylthiophene)(PMOMT), poly (3-methyl-4-cyanothiophene) (PMCNT) and poly (3-methoxy-4-cyanothiophene) (PMOCNT), by using SCF-CNDO/2-CO method. The goal is to discuss the influence of these substituents on the band structure of PT.
The calculated results showed that all of the 3-substituted PTs have coplanar configurations while the 3,4-disubstituted PTs will be nonplanar if the two substituents have a large steric hindrance (such as PDMT). From the band structures of these substituted PTs, we got the conclusions as follows:
1. The substitution of H atom by electron-donating or electron-withdrawing groups will make Eg narrower and the Ess of 3,4-disubstituted PTs are even narrower than those of 3-substituted PTs.
2. When the two substituents of the 3,4-disubstituted PTs have a large steric interaction with the S atoms of the neighbouring rings, such as poly (3,4-dimethylthiophene),its energy gap (Eg) will be much wider.
3. As the H atoms of 3 or 3, 4-position of PT are substituted by electron-donating groups, both of the I.P. and E.A. become lower, whereas by electron-withdrawing group, both of them become higher. So it is expected that the electron-donating group substituted PTs are favourable to p-type doping while the electron-withdrawing group substituted PTs to n-type doping.

Key words: Poly-substituted thiophene, Effect of substituents, Self consisitent field crystal orbital, Electronic structure