Stepwise construction of novel zig-zag shaped thiophene-based back-to-back terpyridine ligands with acetylenic tethers

A series of structurally well-defined molecular-scale wires bearing one to five 2,5-diethynyl-3,4-dibutylthiophene spacers and 2,2′:6′,2′′-terpyridine capping units were synthesized by a combination of cross-coupling reactions and deprotection steps. Palladium-catalyzed cross-coupling of halogenated thiophene units with acetylene grafted terpyridine effectively yields ethynylated thiophenes. Deprotection of the propargylic fragment provides additional building blocks, which could be used in an iterative sequence of reactions. Reliable and practical synthetic routes are now available for the construction of very large polytopic frameworks.