Synthesis, Structure, and Optical Property of [6]Cyclo-1,2-naphthylene

A one-pot procedure with cobalt-mediated oxidation of 2,2'-dilithio-1,1'-binaphthyl by ferrocenium salts afforded the chiral cyclic hexamer of naphthylene, [6]cyclo-1,2-naphthylene (1). The molecular structure of 1 was determined by single crystal X-ray crystallography and NMR analyses, revealing its cyclic structure with an approximate D₃ symmetry. Compound 1 exhibits blue emission at 383 nm with high photoluminescence quantum yield of 97 %, which can be attributed to its rigid twelve-membered ring structure. Optical resolution of 1 by chiral HPLC allowed for the evaluation of its chiroptical properties. Each enantiomer exhibits circular dichroism with complex Cotton effects, which are grouped into three positive or three negative couplets. Circularly polarized luminescence is observed at 383 nm with an anisotropy factor |g_lum| on the order of 10^-4. The high photoluminescence quantum yield and the CPL properties of 1 indicate its potential application as a CPL emitter.