Chemical and electrochemical oxidation of thiophene-pyridine and thiophene-pyrimidine co-oligomers in solutions.
Chemical and electrochemical oxidation of thiophene-pyridine and thiophene-pyrimidine co-oligomers in solutions.
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DOI：
10.1021/jp071614u
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发表时间：
2007-06
期刊：
影响因子：
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通讯作者：
A. Kumagai;Hiroki Fukumoto;Takakazu Yamamoto
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文献类型：
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作者：
A. Kumagai;Hiroki Fukumoto;Takakazu Yamamoto
本文研究了三种偶联共聚物Py-Th-(Th)n-Th-Py （Py =吡啶单元；Th =噻吩单元；5a, n = 1; 6a, n = 2）、Th-Py-(Th)n-Py-Th （5b: n = 1; 6b: n = 2）和Pym-Th-(Th)n-Th-Pym （Pym =嘧啶单元；5c: n = 1; 6c: n = 2）在溶液体系中的化学和电化学氧化（或p掺杂）。用NOBF(4)进行化学氧化，在紫外-可见光谱中有等吸点。NOBF(4)氧化后，5a在CH(2)Cl(2)中418 nm的紫外-可见吸收峰移至456 nm。氧化后的5a很容易被N(2)H(4)还原，得到5a的原始紫外-可见光谱，5b、6b和5c的氧化还原行为相似。在NOBF4氧化过程中，在[NOBF4] = 1.3 × 10（-6）、4 × 10（-6）、7 × 10（-6）和9 × 10(-6) M时，对5a、6b、5b和5c的氧化共聚物（氧化共聚物）/（原始中性共聚物）的比值为1。所得数据被认为反映了共聚物的易氧化性，其易氧化性受共聚物中含n芳香单元的电子接受性质和共聚物有效π共轭长度的影响。5a的循环伏安图显示3对氧化还原对，相对于Ag+/Ag，其阳极峰电流电位分别为Epa = 0.75、1.10和1.34 V。第一个氧化峰归属于5a的单电子氧化，5a和5c的第一个阳极峰(i)的电子电流与（扫描速率）1/2成正比。根据i-（扫描速率）1/2关系，估计5a和5c的扩散常数D分别为9.6 x 10（-6）和1.7 x 10(-5) cm2 s（-1）。5b与末端噻吩单元的CV数据表明5b发生了电化学氧化聚合。
Chemical and electrochemical oxidation (or p-doping) of three types of pi-conjugated co-oligomers, Py-Th-(Th)n-Th-Py (Py = pyridine unit; Th = thiophene unit; 5a, n = 1; 6a, n = 2), Th-Py-(Th)n-Py-Th (5b: n = 1; 6b: n = 2), and Pym-Th-(Th)n-Th-Pym (Pym = pyrimidine unit; 5c: n = 1; 6c: n = 2), in solution systems has been studied. The chemical oxidation with NOBF(4) proceeded with isosbestic points in the UV-vis spectrum. The UV-vis absorption peak of 5a at 418 nm in CH(2)Cl(2) shifted to 456 nm after oxidation of 5a with NOBF(4). The oxidized 5a was easily reduced by N(2)H(4) to give the original UV-vis spectrum of 5a, and 5b, 6b, and 5c behaved similarly in the oxidation and reduction. In the oxidation by NOBF4, an (oxidized co-oligomer)/(original neutral co-oligomer) ratio of 1 was attained at [NOBF4] = 1.3 x 10(-6), 4 x 10(-6), 7 x 10(-6), and 9 x 10(-6) M for 5a, 6b, 5b, and 5c, respectively. The obtained data are considered to reflect the ease of oxidation of the co-oligomer, which is affected by the electron-accepting nature of the N-containing aromatic unit in the co-oligomer and effective pi-conjugated length of the co-oligomer. The cyclic voltammogram of 5a showed three redox couples with anodic peak current potentials of Epa = 0.75, 1.10, and 1.34 V versus Ag+/Ag, respectively. The first oxidation peak was assigned to one-electron oxidation of 5a, and electronic current of the first anodic peak (i) of 5a and 5c was proportional to (scanning rate)1/2. From the i- (scanning rate)1/2 relationship, diffusion constants, D's, of 5a and 5c were estimated to be 9.6 x 10(-6) and 1.7 x 10(-5) cm2 s(-1), respectively. CV data of 5b with the terminal thiophene units indicated occurrence of electrochemical oxidative polymerization of 5b.