Two-Dimensional Self-Assembly of Bodipy Derivatives with Different Functional Groups at the Liquid-Solid Interface

Abstract

The 4,4-difluoro-boradiazaindacene (BODIPY) molecule possesses a rigid aromatic backbone, which facilitates the formation of self-assemblies and aggregates. However, most current studies on the self-assemblies of BODIPY derivatives have relied on spectroscopic methods to indirectly gather information about the self-assembled structures. In this study, we presented three BODIPY derivatives (B-3OC12, B-3OC12-2I, and B-DOB-2OC12) that shared the same core but were decorated with different functional groups. The self-assembly structures were revealed using scanning tunneling microscopy (STM) in combination with density functional theory (DFT). The results showed that all the molecules self-assembled into lamellar structures. When modified with three dodecyloxy chains or with the introduction of additional halogen atoms, the B-3OC12 and B-3OC12-2I molecules tended to distribute in a staggered form to build a tetramer or dimer. In contrast, the B-DOB-2OC12 molecule, which contains a dioxaborole group, self-assembled in a head-to-tail manner. These results demonstrated that BODIPY derivatives self-assembled into different structures, depending on their distinct patterns of intermolecular interactions influenced by functional groups.

Keywords: BODIPY, Self-assembly, Scanning tunneling microscopy (STM), Functional groups, Halogen interaction