Post-Ugi synthesis of furo[2,3-c]isoquinolines with expanded π-conjugation display emission upon induced aggregation

Abstract

Furo[2,3-c]isoquinolines are tricyclic heteroaromatic structures that can be obtained by coupling the Ugi reaction with a complex Pd-mediated secondary transformation. These compounds are usually blue emitters which can be shifted to green emitters modulating the electronic properties of the substituents as well as their position on the scaffold. Here we present a different strategy for influencing the emission properties, that is the extension of the conjugation of the scaffold after the formation of the tricyclic heterocycle. This allowed us to synthesize a new library of highly conjugated and structurally complex fluorophores displaying considerable emission light-up upon induced aggregation. The electronic structure of absorption and emission of the chromophores was rationalized by cLR-CAM-B3LYP calculations.