Enhancing Dual‐State Emission in Maleimide Fluorophores through Fluorocarbon Functionalisation

Herein, a library of trifluoroethyl substituted aminomaleimide derivatives are reported with small size and enhanced emissions in both solution and solid-state. A diCH2CF3 substituted aminochloromaleimide exhibits the most efficient dual-state emission (Φf >50 % in solution and solid-state), with reduced quenching from protic solvents. This is attributed to the reduction of electron density on the maleimide ring and suppressed π-π stacking in the solid-state. This mechanism was explored in-depth by crystallographic analysis, and modelling of the electronic distribution of HOMO-LUMO isosurfaces and NCI plots. Hence, these dual-state dyes overcome the limitations of single-state luminescence and will serve as an important step forward for this rapidly developing nascent field. The authors thank the Ministerio de Economia y Competitividad (MINECO) of Spain (project: PID2019-104772GB-I00) and the Basque Government (project IT1346-19), and the Leverhulme Trust (RPG-2016-452). Dr. Thomas R. Wilks and Dr. Yujie Xie are thanked for helpful discussions and Chi Tsang (University of Birmingham) for high resolution mass spectroscopy analysis. The authors acknowledge the computational resources, and technical and human support provided by the DIPC.