From Short- to Long-Range Chiral Recognition on Surfaces: Chiral Assembly and Synthesis.

Research on chiral behaviors of small organic molecules at solid surfaces, including chiral assembly and synthesis, can not only help unravel the origin of the chiral phenomenon in biological/chemical systems but also provide promising strategies to build up unprecedented chiral surfaces or nanoarchitectures with advanced applications in novel nanomaterials/nanodevices. Understanding how molecular chirality is recognized is considered to be a mandatory basis for such studies. In this review, a series of recent studies in chiral assembly and synthesis at well-defined metal surfaces under ultra-high vacuum conditions are outlined. More importantly, the intrinsic mechanisms of chiral recognition are highlighted, including short/long-range chiral recognition in chiral assembly and two main strategies to steer the reaction pathways and modulate selective synthesis of specific chiral products on surfaces.

Modulation on the Iron Centers by Selective Synthesis of Organic Ligands with Stereo-Specific Conformations.

Advanced fabrication of surface metal-organic complexes with specific coordination configuration and metal centers will facilitate to exploit novel nanomaterials with attractive electronic/magnetic properties. The precise on-surface synthesis provides an appealing strategy for in situ construction of complex organic ligands from simple precursors autonomously. In this paper, distinct organic ligands with stereo-specific conformation are separately synthesized through the well-known dehalogenative coupling. More interestingly, the exo-bent ligands promote the mono-iron chelated complexes with the Fe center significantly decoupled from the surface and of high spin, while the endo-bent ligands lead to bi-iron chelated ones instead with ferromagnetic properties.

Long-Range Chirality Recognition of a Polar Molecule on Au(111).

Chiral molecular self-assemblies were usually achieved using short-range intermolecular interactions, such as hydrogen-, metal-organic, and covalent bonding. However, unavoidable surface defects, such as step edges, surface reconstructions, or site dislocations may limit the applicability of short-range chirality recognition. Long-range chirality recognition on surfaces would be an appealing but challenging strategy for chiral reservation across surface defects at long distances. Now, long-range chirality recognition is presented between neighboring 3-bromo-naphthalen-2-ol (BNOL) stripes on an inert Au(111) surface across the herringbone reconstruction as investigated by STM and DFT calculations. The key to achieving such recognition is the herringbone reconstruction-induced local dipole accumulation at the edges of the BNOL stripes. The neighboring stripes are then forced to adopt the same chirality to create the opposite edged dipoles and neutralize the neighbored dipole moments.