Synthesis of Highly Twisted, Nonplanar Aromatic Macrocycles Enabled by Axially Chiral 4,5-Diphenylphenanthrene Building Block

The synthesis, structures, and properties of highly twisted, nonplanar aromatic macrocycles are described. These macrocycles with an approximately 90° twist angle were synthesized by an effective synthetic approach through a quadruple Suzuki-Miyaura coupling of 4,5-bisarylphenanthrene as a novel axially chiral nonplanar building block. By varying the cross-coupling partner as the spacer, a family of twisted macrocycles was synthesized, allowing for a systematic study of the effect of the spacer on macrocycle shape and photophysical properties. For example, a unique macrocyclic aggregation-induced emission (AIE) emitter with double tetraphenylethylene units as the spacers was readily synthesized. Furthermore, attributed to its conformationally restricted twisted structure, a 3,6-disubstituted-1,8-naphthalimide-incorporated macrocycle showed remarkable solvatofluorochromism with high fluorescence quantum yields. The excellent conformational stability of these macrocycles further enabled complete enantiomeri...