[n]Cyclo‐3,6‐phenanthrenylenes: Synthesis, Structure, and Fluorescence

Five congeners of [n]cyclo-3,6-phenanthrenylene with 3, 4, 5, 7, and 8 panels were obtained from one-pot macrocyclization of dibromophenanthrene, and their crystal structures with diverse molecular shapes were revealed by X-ray crystallography. The compounds, except the four-panel congener, were highly fluorescent in solution, with quantum yields up to 85 %. The least fluorescent four-panel congener showed the smallest change in its absorption spectrum from that of monomeric phenanthrene, which provided an interesting structure-activity relationship for fluorescent macrocycles to guide future studies.