Substrate-directed chiral selectivity of molecular self-assembled and covalent structures

Abstract

Controlling the synthesis of low-dimensional chiral nanostructures on solid surfaces has attracted tremendous interest in recent years. Herein, we report a study showing substrate-directed chiral selectivity of molecular self-assemblies and polymers. Depositing prochiral 2,6-dibromo-anthracene (DBA) on Ag(111) and Ag(100) held at 120 K leads to the formation of a homochiral self-assembled structure and racemic self-assembly, respectively. Thermal annealing induces the stepwise formation of organometallic and covalent structures on the two surfaces. Similar to the low-temperature case, high chiral selectivity is achieved on Ag(111), where organometallic chains and covalent polymers are composed of homochiral DBA molecules, while poor chiral selectivity is found on Ag(100). This difference is presumably attributed to the lattice symmetry and substrate reactivity, as supported by the contrast experiments carried out on Au(111) and Cu(111). This work provides guidance for the construction of chiral low-dimensional nanomaterials on surfaces.