In this study, a series of rationally designed emissive phenanthrene derivatives were synthesized and their aggregation-induced emission (AIE) properties in tetrahydrofuran (THF)/water mixtures were investigated. Two tetraphenylethene (TPE) segments were conjugated to both ends of the phenanthrene core at the para-positions and meta-positions, resulting in pTPEP and mTPEP derivatives, respectively. While the TPE-conjugated phenanthrene derivatives did not show any emission when dissolved in pure THF, they showed strong sky-blue emissions in water-THF mixtures, which is attributed to the restriction of intramolecular motions of TPE segments by aggregation. Furthermore, silica nanoparticles loaded with these AIE-active compounds were prepared and proved to be promising intracellular imaging agents.
Keywords: aggregation; bio-imaging; emission; silica nanoparticles; tetraphenylethene.