On-surface synthesis and spontaneous segregation of conjugated tetraphenylethylene macrocycles.

Creating conjugated macrocycles has attracted extensive research interest because their unique chemical and physical properties, such as conformational flexibility, intrinsic inner cavities and aromaticity/antiaromaticity, make these systems appealing building blocks for functional supramolecular materials. Here, we report the synthesis of four-, six- and eight-membered tetraphenylethylene (TPE)-based macrocycles on Ag(111) via on-surface Ullmann coupling reactions. The as-synthesized macrocycles are spontaneously segregated on the surface and self-assemble as large-area two-dimensional mono-component supramolecular crystals, as characterized by scanning tunneling microscopy (STM). We propose that the synthesis benefits from the conformational flexibility of the TPE backbone in distinctive multi-step reaction pathways. This study opens up opportunities for exploring the photophysical properties of TPE-based macrocycles. On-surface synthesis is a useful tool to produce extended macrocyclic structures with atomic precision, with only one type of macrocycle typically formed through on-surface coupling reactions. Here, distinct domains of four-, six- and eight-membered tetraphenylethylene-based macrocycles are synthesized on Ag(111) as segregated large-area mono-component crystals. [ABSTRACT FROM AUTHOR]