Highly Fluorescent, π‐Extended Indenopyrido[2,1‐<i>a</i>]isoindolone Derivatives Prepared by a Palladium‐Catalysed Cascade Reaction

Abstract

Abstract A new family of heterocyclic pentacyclic compounds have been prepared by a cascade reaction involving 2,5‐dihalopyridines and (2‐formylphenyl)boronic acids. Most of the compounds exhibit high quantum yields of fluorescence in dichloromethane. In some cases, small changes in the substitution pattern caused fluorescence quenching. To rationalize this effect, a detailed photophysical study combined with electrochemical and computational studies was performed on four representative derivatives. It appears that the fluorescence quenching is caused by a thermally activated non‐radiative deactivation process that can be prevented in a rigid matrix such as ethanol at 77 K or a PMMA polymer.