Two-dimensional tessellation by molecular tiles constructed from halogen\u2013halogen and halogen\u2013metal networks

Fang Cheng,Kian Ping Loh,Hai Xu,Yan Shao,Zhixin Hu,Xue-Jun Wu,Wei Ji,Zijing Ding,Xuefeng Lu,Jishan Wu

doi:10.1038/s41467-018-07323-6

Abstract

Molecular tessellations are often discovered serendipitously, and the mechanisms by which specific molecules can be tiled seamlessly to form periodic tessellation remain unclear. Fabrication of molecular tessellation with higher symmetry compared with traditional Bravais lattices promises potential applications as photonic crystals. Here, we demonstrate that highly complex tessellation can be constructed on Au(111) from a single molecular building block, hexakis(4-iodophenyl)benzene (HPBI). HPBI gives rise to two self-assembly phases on Au(111) that possess the same geometric symmetry but different packing densities, on account of the presence of halogen-bonded and halogen–metal coordinated networks. Sub-domains of these phases with self-similarity serve as tiles in the periodic tessellations to express polygons consisting of parallelograms and two types of triangles. Our work highlights the important principle of constructing multiple phases with self-similarity from a single building block, which may constitute a new route to construct complex tessellations.

Highlights

Molecular tessellations are often discovered serendipitously, and the mechanisms by which specific molecules can be tiled seamlessly to form periodic tessellation remain unclear
The mesogenic molecular building block, namely HPBI44,45, is a nonplanar molecule composed of a central benzene ring flanked by six out-of-plane piodophenyl groups with a lateral width of about 1.5 nm (Fig. 1a)
A single HPBI molecule consists of a flower-shaped feature with six-fold symmetry, which is consistent with the C6 symmetry of the molecule

Summary

Introduction

Molecular tessellations are often discovered serendipitously, and the mechanisms by which specific molecules can be tiled seamlessly to form periodic tessellation remain unclear. HPBI gives rise to two self-assembly phases on Au(111) that possess the same geometric symmetry but different packing densities, on account of the presence of halogen-bonded and halogen–metal coordinated networks Subdomains of these phases with self-similarity serve as tiles in the periodic tessellations to express polygons consisting of parallelograms and two types of triangles. Hexakis(4-iodophenyl)benzene (HPBI), a D6h symmetric molecule, is used as a building block to fabricate two periodic supramolecular phase types on Au(111) These selfassembly patterns have the same lattice symmetry but different packing densities; the variation in packing density is attributed to networks formed by halogen bonds[40,41] and halogen–Au coordination, as verified via scanning tunnelling microscopy (STM) and density function theory (DFT) calculations. The selfsimilarity of these two phases favours interweaving between the phases to form higher-order supramolecular phases; this mechanism constitutes a new method for constructing complex 2D tessellations through the interplay between intermolecular and molecule–substrate interactions[42,43]

Methods

Results

Conclusion