A novel polythiophene bearing a pendant terpyridine moiety has been synthesized by electrochemical polymerization of a new thiophene monomer, namely 4'-(2,2':5',2 ''-terthien-3'-ethynyl)-2,2':6',2 ''-terpyridine (TAT). The insertion of a conjugated ethynyl spacer between the terthiophene and the terpyridine fragments provides for an effective extension of the delocalization of electrons within the structural unit and the polymer as a whole. The synthesis and characterization of the relevant monomer, the electrosynthesis of the corresponding polymer and its electrochemical, UV-visible spectroelectro-chemical and IR characterization are described. Finally, a comparison between the electrochemical, spectroscopic, and spectroelectrochemical properties of PTAT and the analogue, saturated-spacer PTTT (TTT 4'-[(2,2': 5',2 ''-terthien-3'-yl)methoxy]- 2,2': 6',2 ''-terpyridine) polymer is discussed. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 3513-3523, 2011