Self-sorting multiple building blocks for correctly positioning molecules through orthogonal recognition is a promising strategy for construction of a hierarchical self-assembled molecular network (SAMN) on a surface. Herein we report...

We herein investigated the effect of the number of alkoxy chains on the two-dimensional selfassembly of a trigonal molecular building block. To this end, a dehydrobenzo[12]annulene (DBA) derivative, DBA-OC14-OC1 having three tetradecyloxy chains and three methoxy groups in an alternating manner, was synthesized. Scanning tunneling microscopy (STM) observations at the 1,2,4-trichlorobenzene (TCB)/graphite interface revealed that DBA-OC14-OC1 forms three monolayer structures, porous honeycomb, parallelogram, and hexagonal A structures. At the 1phenyloctane (PO)/graphite interface, DBA-OC14-OC1 also forms three structures: parallelogram, hexagonal B and dense-linear structures. In contrast to the previously reported DBA derivative DBA-OC14 having six tetradecyloxy chains, DBA-OC14-OC1 shows structural polymorphism with a variety of alkyl chain interaction modes. Since in the observed patterns DBA-OC14-OC1 adopts a low symmetric Cs or C1 geometry, the variation of the interaction modes and the resulting network patterns likely originate from the conformational flexibility on surface of this DBA by decreasing number of alkyl chains. Molecular mechanics simulations gave insight in the structural and energy aspects of this pattern formation. We also discussed the role of solvents, TCB and PO, on the polymorph formation.

Grain boundaries in polycrystals have a prominent impact on the properties of a material, therefore stimulating the research on grain boundary engineering. Structure determination of grain boundaries of molecule‐based polycrystals with submolecular resolution remains elusive. Reducing the complexity to monolayers has the potential to simplify grain boundary engineering and may offer real‐space imaging with submolecular resolution using scanning tunneling microscopy (STM). Herein, the authors report the observation of quasi‐periodic nanoscale chirality switching in self‐assembled molecular networks, in combination with twinning, as revealed by STM at the liquid/solid interface. The width of the chiral domain structure peaks at 12–19 nm. Adjacent domains having opposite chirality are connected continuously through interdigitated alkoxy chains forming a 1D defect‐free domain border, reflecting a mirror twin boundary. Solvent co‐adsorption and the inherent conformational adaptability of the alkoxy chains turn out to be crucial factors in shaping grain boundaries. Moreover, the epitaxial interaction with the substrate plays a role in the nanoscale chirality reversal as well.