Synthesis and Polymerization Behavior of Tridentate Diacetylene Hosts

The synthesis of three new tridentate ligands capable of forming large cavities for encapsulation of organoiodides is described. Each compound consists of a central heterocyclic “base unit” linked by acetylenes to two heterocyclic “arm” units. The base and the arm unit are each either a 2,6-disubstituted pyridine or a 2,5-disubsituted thiophene ring. The terminal end of each arm unit is connected to a (butoxycarbonyl)methylurethanyl (BCMU) moiety by way of a diacetylene linkage. This serves as a polymerogenic group that helps align the diacetylenes for topotactic polymerization. The triaryl ring systems are constructed through a series of aryl bromide/protected acetylene coupling steps, followed by deprotection and further coupling. Two of the compounds polymerize photochemically and all three polymerize thermally.