Hidden Order and Haldane-Like Phase in Molecular Chains Assembled from Conformation-Switchable Molecules

Abstract

Topological properties of matters have attracted tremendous interest in the past years due to the scientific and technological importance. It is of great interest to discover the analogs of topological phases in molecular architectures, if the key constituents of the phases are properly mimicked. Using scanning tunneling microscopy, we demonstrate that quasi-1D molecular chains assembled from conformation-switchable dibenzo[ g, p]chrysene molecules show hidden antiparallel order analogous to the hidden antiferromagnetic order in the Haldane phase, a known topological phase of quantum spin-1 chains. This is realized by mimicking the spin degree of freedom with the intramolecular helicene chiral switches and by emulating the interspin antiferromagnetic coupling with intermolecular homochiral coupling. The discovery of the molecular analog of topological matters may inspire the search of molecular architectures with nontrivial topological properties.

On-Surface Synthesis of Self-Assembled Covalently Linked Wavy Chains with Site-Selective Conformational Switching

“…Alternatively, multiple precursor conformations on surfaces can also be arranged into ordered chains by site-selective conformational switching. 34 For example, two precursor conformations A and B are arranged with AB, AAB, etc. as repeating units.…”

“…Some strategies have been demonstrated to effectively control the molecular conformation, such as the template effect of organometallic intermediates, , new adsorbate surface formed by leaving bromine atoms or distinct substrates, , adjusting molecular concentration, , annealing or tip-induced manipulation, , etc. Alternatively, multiple precursor conformations on surfaces can also be arranged into ordered chains by site-selective conformational switching . For example, two precursor conformations A and B are arranged with AB, AAB, etc.…”

Helical Conformation Tunability via Hydrogen Bonding in Supramolecular Frameworks

“…[12][13][14][15][16][17] Understanding how hydrogen bonding influences the molecular self-assembly is a key step to realize the controllable fabrication and manipulation of functionalized molecules into complex architectures and is crucial for the potential applications such as molecular electronic devices. [18][19][20] With the development of scanning-probe microscopy techniques, high-resolution imaging provides the possibility to characterize the molecular structures directly, 21,22 which delivers an appealing hotbed for investigating the role of hydrogen bonds in molecular self-assembly. Here, we used specifically designed molecules with dynamical molecular conformation as building blocks for self-assembly fabrication, which furnishes a model system for investigating the rich relationships between hydrogen bonding and molecular selfassembly, including the emergent tunable molecular conformation in the molecular framework.…”