Structural Transformation of Tetracarboxylic Acids Self-Assembly Structures Regulated by a Pyridine Derivative

In this work, the self-assembly behaviors of tetracarboxylic acid derivatives (EBTD, BCPTD, and DETD) and their co-assembly behaviors with pyridine derivative PEBP-C8 were investigated by scanning tunneling microscopy (STM) and density functional theory (DFT). EBTD, BCPTD, and EBTD molecules self-assembled into similar regular grid structures by forming O-H···O hydrogen bonds. Especially, with a meta-dicarboxylic group, DETD molecules could aggregate into another kind of dimeric building block, leading to more diversified self-assembly nanostructures. With the introduction of PEBP-C8, all of the O-H···O hydrogen bonds in EBTD and BCPTD systems were broken and O-H···N hydrogen bonds were formed with PEBP-C8. In contrast, for the DETD/PEBP-C8 system, partial O-H···O hydrogen bonds were retained along with the new O-H···N bonds with PEBP-C8. Both EBTD and BCPTD co-assembled with PEBP-C8 to form acid-pyridine-acid-pyridine nanostructures. Nevertheless, DETD not only assembled with PEBP-C8 into an acid-pyridine-acid-pyridine nanostructure but also formed a pyridine-acid-acid-pyridine nanostructure.