Elucidating the molecular structural origin of efficient emission across solid and solution phases of single benzene fluorophores.

Achieving high quantum yields for organic fluorophores in both solution and in the polycrystalline solid state is a significant yet challenging goal, as most fluorophores typically emit effectively in only one phase. In this study, we introduce 1,1'-(2,5-dimethoxyterephthaloyl)-bis(glutraimide) (TGlu), a novel 'single benzene'-based organic fluorophore featuring an alkoxy donor and an N-acyl-glutarimide acceptor. TGlu achieves close-to-unity fluorescence quantum yields in both solution and in the polycrystalline state. Through systematic studies involving four additional structural analogues of TGlu, we unveiled that the acceptor group within the single benzene core plays a crucial steric and electronic role in achieving high fluorescence efficiency in both phases. Furthermore, we demonstrated the versatility of this new fluorophore in various applications. In solution, TGlu serves as a highly effective photocatalyst for photoinduced energy/electron transfer reversible addition-fragmentation chain-transfer polymerization while in its single-crystal form, TGlu exhibits highly efficient waveguiding properties.