Role of intrinsic hydrogen bonds in the assembly of perylene imide derivatives in solution and at the liquid-solid interface.

The impact of hydrogen bond formation on the supramolecular assembly of two perylene imide derivatives (PMAMI and PDINH) was systematically investigated in solution and at the liquid-solid interface. PDINH has intrinsic hydrogen bond sites, but this is not the case for PMAMI. The solution assembly was explored by morphological methods (SEM, AFM, TEM and cryo-TEM) and spectral characterization (UV-vis, FL, XRD, and FTIR spectra). The surface assembly at the liquid-solid interface was detected by scanning tunneling microscopy (STM). It was found that in a mixed solution (THF/MeOH, 10 v%/90 v%), PMAMI formed nanofibers together with large sheet structures and PDINH assembled into uniform nanosheets, suggesting different molecular packing routes. The assembled structures could be adjusted by varying the solvent polarity for both molecules. At the liquid-solid interface, clearly distinguished surface nanostructures from PMAMI and PDINH were easily observed. Based on all spectral and morphological characterizations, it was suggested that in solution the assembly of PMAMI was mainly derived by π-π stacking interactions; on the other hand, the synergetic interaction of hydrogen bonds and π-π stacking was the reason for the hierarchical assembly of PDINH. Hydrogen bonds could be formed both for PMAMI and PDINH and stabilized nanostructures at the liquid-solid interface. This investigation could be useful in designing perylene imide-based building blocks for fabricating supramolecular assemblies with predetermined nanostructures and properties.