Synthesis of novel poly(dithienylpyridines)

This paper describes the chemical and electrochemical synthesis of novel copolymers of thiophene and pyridine. Di-iodination of 3-hydroxypyridine 12 followed by O-substitution gave a series of ethers 14b-d and esters/carbamates 15a-d which were reacted with the stannylated bithiophene derivative 17 in a Stille cross-coupling reaction yielding poly (1b-d) and poly (2a-d) respectively. These chemical polymerisation reactions generally resulted in highly insoluble materials which were difficult to characterise. Ethers 14b-d and esters/carbamates 15a-d gave O-substituted 3-hydroxy-2,6-di(2-thienyl)pyridines 1b-d and 2a-d respectively in Stille cross-coupling reactions with the stannylated thiophene 16. Ethers 1b-d underwent electrochemical polymerisation allowing the synthesis of O-alkylated polymers, poly (1b-d), with electrochemical band-gaps of 1.4 to 1.6 eV. In contrast, the esters/carbamates 2a-d could not be electropolymerised.