Triptycene‐Based Organic Nanosheet Assemblies via Reversible Boronic Ester Formation: Alkyl Chain Length‐Dependent Formation and Aggregation

A bottom-up strategy for the preparation of triptycene-based organic nanosheet assemblies through reversible boronic ester formation is presented. The triptycene scaffold enables the orthogonal placement of alkyl substituents and boronic ester-forming sites, providing a molecular platform to examine how peripheral alkyl chains influence nanosheet formation and aggregation. Time-dependent microscopy observations revealed alkyl-chain-length-dependent assembly behavior. Hexyl-substituted precursors afforded sheet-like domains at an earlier stage, whereas methyl- and ethyl-substituted analogs showed slower formation of less-defined nanosheet-like morphologies. These results indicate that longer alkyl chains are associated with earlier formation of sheet-like domains and stronger aggregation; however, this alkyl-chain effect is described as an empirical trend rather than a definitively established mechanism. Infrared spectroscopy supported boronic ester formation, and single-crystal structures of partial molecular analogs confirmed the orthogonal arrangement of the alkyl substituents relative to the framework-forming units. Absorption measurements showed a slight red-shift for the nanosheet assemblies relative to the corresponding reference compounds, consistent with modest extension of electronic communication within the boronic ester-linked framework. This study provides a case study showing that peripheral alkyl substituents can influence the formation and aggregation behavior of triptycene-based organic nanosheet assemblies, offering useful insight into the development of dispersible 2D organic materials.