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

Abstract

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.

Fluorescence Enhancement of Aromatic Macrocycles by Lowering Excited Singlet State Energies

“…Other relevant compounds were synthesized by adopting different methods. One-pot cyclization of dibromide 1b with a Yamamoto-type coupling reaction afforded a macrocycle ( 4g ) furnished with three methylene/acetal bridges (Scheme a). , Macrocycle 6 was designed by replacing one two-phenylene unit with one alkane chain. Macrocycle 6 was synthesized from 1,5-hexadiene, which was hydroborylated and coupled with 1a for the final Ni-mediated cyclization (Scheme b).…”

“…A unique series of organic materials has been designed simply by arraying aromatic panels in macrocyclic structures . For instance, the circularly polarized luminescence of organic molecules was dramatically enhanced by an intense magnetic transient dipole moment induced in belt-persistent macrocycles, and a magnetic-field-induced enhancement of electroluminescence, i.e., a magneto-electroluminescence effect, was observed with [ n ]­cyclo- meta -phenylene ([ n ]­CMP, n = 6; Figure ) embedded in a single-layer organic light-emitting device (OLED). , Furthermore, a single-layer OLED with a high internal quantum efficiency was fabricated by solely using hydrocarbon macrocycles, including [3]­cyclo-3,6-phenanthrenylene ([3]­CPhen 3,6 ) as an efficient emitter. , However, the structural factors of macrocycles for efficient fluorescence have not been elucidated. Specifically, [6]­CMP is a poor emitter with a photoluminescent quantum yield (ϕ) of 6%, whereas its vinylene-bridged congener, [3]­CPhen 3,6 , is an excellent emitter with an efficient yield of ϕ = 75% (Figure ).…”

“…Specifically, [6]­CMP is a poor emitter with a photoluminescent quantum yield (ϕ) of 6%, whereas its vinylene-bridged congener, [3]­CPhen 3,6 , is an excellent emitter with an efficient yield of ϕ = 75% (Figure ). However, our understanding of the structure–fluorescence relationships of macrocycles is still immature, and the origins of such considerable differences in ϕ values are unclear. In this study, we designed and synthesized a series of [6]­CMP-related macrocycles that differed in the number of phenylene/phenanthrenylene panels having different degrees of π-conjugation and flexibility.…”

Synthesis, Photophysical and Electrochemical Study of 1,3,6,8‐Tetraarylsubstituted X‐Shaped Phenanthrene Derivatives

“…Phenanthrene has a curved structure that enables it to serve as a core building block for the synthesis of unique functional π-electron molecules such as conjugated macrocycles, [14][15][16][17][18] helicenes [19][20][21][22][23][24][25][26] and phenacenes. [27][28][29] Efforts have been con-ducted to extend the conjugation of phenanthrenes by introducing aryl substituents at 3-and 6-positions where its HOMO and LUMO orbital coefficients are large.…”