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摘要
The article contains a comprehensive study regarding the synthesis and properties of novel polythiophenes, where bithiophene units are linked with either ethynyl or bisethynylarylenyl bridges. A convenient and selective method for lithiation of 2,2%26apos;-bithiophene, with the aid of n-butyllithium in dialkyl ether/n-hexane solution under mild conditions (-5 to 5 degrees C), is also presented. The lithiation, followed by the addition of iodine solution at room temperature constituted a robust method towards the synthesis of 5-iodo-2,2%26apos;-bithiophene, which was then used as a key substrate in the Sonogashira-type cross-coupling reactions. The coupling of 5-ethynyl-2,2%26apos;-bithiophene with 5-iodo-2,2%26apos;-bithiophene, mediated by [PdCl2(PPh3)(2)]/CuI couple, resulted in the formation of 1,2-bis(2,2%26apos;-bithiophene-5-yl)ethyne. The synthesized monomers of Bt-A-Bt (where Bt = 2,2%26apos;-bithiophene-5-yl) type, namely: 1,2-bis(2,2%26apos;-bithiophene-5-yl)ethyne, 1,4-bis(2,2%26apos;-bithiophene-5-yl)buta-1,3-diyne and 1,4-bis(2,2%26apos;-bithiophene-5-ylethynyl)benzene were transformed into conducting polymers in an electrochemical oxidation process. The influence of the A bridge on the stability, luminescent and electrochemical behavior was thoroughly studied. The polymers present an extraordinary stability during multiple n- and p-doping. The experimental results were also investigated theoretically, using DFT approach. For each polymer calculations of the frontier orbital energies and the corresponding E-g value were done using periodic boundary conditions. For polythiophene derived from 1,2-bis-(2,2%26apos;-bitiophene-5-yl)ethyne the value of the band gap was also estimated using an oligomeric approximation. Furthermore, the presented compounds revealed an enhanced fluorescent activity, especially in the case of a monomer with bisethynylphenylene bridge and the corresponding polymer.
- 出版日期2013-2-1
