Conjugated Trimeric Scaffolds Accessible from Indolyne Cyclotrimerizations: Synthesis, Structures, and Electronic Properties.

We report the design and synthesis of a new class of indole-based conjugated trimers. The targeted compounds are accessed from in situ generated, highly reactive indolyne intermediates using Pd-catalyzed cyclotrimerization reactions. By harnessing three indolyne isomers, six isomeric indole trimers are accessible, none of which have been previously synthesized. Using computational analysis, we describe the structural and photophysical properties of these unique compounds. This study showcases the use of indolynes in transition metal-catalyzed reactions, while providing access to a new class of conjugated trimers, including highly bent heteroaromatic compounds. Computations indicate that, despite differences in planarity between the molecules, the photophysical properties of each trimer are derived from the N-methylindole building block. Excited state behavior follows predicable patterns.