Synthesis of Novel Biocompatible Thienopyrimidine Chromophores with Aggregation-Induced Emission Sensitive to Molecular Aggregation

Biocompatible luminogens with aggregation-induced emission (AIE) have several applications in the biology field, such as in detecting biomacromolecules bioprobes and in bioimaging. Due to their bioactivities and light-emitting properties, many heterocyclic compounds are good candidates for such applications. However, heterocyclic pi-conjugated systems with AIE behavior remain rare as strong intermolecular pi-pi interactions usually quench their emission. In this work, new thienopyrimidine heterocyclic compounds were synthesized and their structures were verified by elemental analysis and Fourier transform infrared (FT-IR), H-1 nuclear magnetic resonance (NMR), and C-13 NMR spectra. The photophysical properties of some compounds were investigated in the solution and solid states. Density functional theory calculations were also performed to confirm the observed photophysical properties of the compounds. The studied dyes displayed ATE properties with spectral shapes related to the aggregate structure and a quantum yield up to 10.8%. The emission efficiency of the powder is attributed to the incorporation of multiply rotatable and twisted aryl groups to the fused heterocyclic moieties. The dyes also showed high thermal stability and potent antimicrobial activities against numerous bacterial and fungal strains. Additionally, the cytotoxicity of the new compounds was evaluated against the Caco-2 cell line, and molecular docking was used to investigate the binding conformation of the most effective compound with the MNK2 enzyme. Therefore, the presented structures may potentially be used for bioapplications.