π-Conjugated soluble and fluorescent poly(thiophene-2,5-diyl)s with phenolic,hindered phenolic and p-C6H4OCH3 substituents. Preparation,optical properties,and redox reaction

Dehalogenation polycondensation of 3-(4-methoxyphenyl)-2,5-dibromothiophene with Mg and a zerovalent nickel complex as well as chemical oxidative polymerization of 3-(4-methoxyphenyl)thiophene with FeCl₃ gives poly3-(4-methoxyphenyl)thiophene-2,5-diyl] P3(4-MeOPh)Th. Treatment of soluble P3(4-MeOPh)Th with BBr₃ converts the OCH₃ group to an OH group and gives poly3-(4-hydroxyphenyl)thiophene-2,5-diyl] P3(4-OHPh)Th. Oxidative polymerization of 3-3,5-di-t-butyl-4-{(trimethylsilyl)oxy}phenyl]thiophene with FeCl₃ in an aqueous medium directly affords another kind of polythiophene with a sterically hindered phenolic group, poly3-(3,5-di-t-butyl-4-hydroxyphenyl)thiophene-2,5-diyl] P3(4-OH-3,5-tBu₂Ph)Th. An organometallic dehalogenation polymerization using a nickel complex also affords P3(4-OH-3,5-tBu₂Ph)Th. All the polymers described above show strong photoluminescence in a region of 500–600 nm. Oxidation of P3(4-OH-3,5-tBu₂Ph)Th with PbO₂ gives stable radical species as confirmed by IR and ESR spectroscopy. Electrochemical redox behavior of the polymers is compared with that of other polythiophenes. © 1997 John Wiley & Sons, Inc.