Synthesis and Two‐Dimensional Chiral Surface Self‐Assembly of a π‐Conjugated System with Three‐Fold Symmetry: Benzotri(7‐Azaindole)

• Published in: Angewandte Chemie International Edition 2021-01, Vol.60 (4), p.1782-1788
• Main Authors: Rodríguez, Luis M., Gómez, Paula, Más‐Montoya, Miriam, Abad, José, Tárraga, Alberto, Cerdá, Jorge I., Méndez, Javier, Curiel, David
• Format: Article
• Language: English
• Subjects: 2D materials; Assembly; benzotri(7-azaindole); Chirality; Hydrogen bonding; Hydrogen bonds; Molecular rotation; spontaneous resolution; Structural stability; Substrates; supramolecular surface chirality; surface self-assembly; Symmetry; Synthesis
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202012100

The synthesis of a novel expanded π‐conjugated system, namely benzotri(7‐azaindole), BTAI, is reported. Its C3h symmetry along with the integration of six complementary donor and acceptor N−H⋅⋅⋅N hydrogen bonds in the conjugated structure promote the 2D self‐assembly on Au(111) over extended areas. Besides, a perfect commensurability with the gold lattice endows the physisorbed molecular film with a remarkable stability. The structural features of BTAI result in two levels of surface chirality: Firstly, the molecules become chiral upon adsorption on the surface. Then, due to the favorable N−H⋅⋅⋅N hydrogen bond‐directed self‐assembly, along with the relative molecular rotation with respect to the substrate, supramolecular chirality manifests in two mirror enantiomorphous domains. Thus, the system undergoes spontaneous chiral resolution. LEED and STM assisted by theoretical simulations have been employed to characterize in detail these novel 2D conglomerates with relevant chiral properties for systems with C3h symmetry. The synthesis of benzotri(7‐azaindole), BTAI, aims at the control of molecular arrangement in the nanoscale. The rational design and location of hydrogen bond donor and acceptor sites promotes the two‐dimensional self‐assembly of this novel conjugated system with C3h symmetry. STM experiments on Au(111) and computational models prove the formation of extended homochiral domains resulting from the spontaneous resolution of the surface enantiomers.