The design and fabrication of well-defined two-dimensional (2D) molecular networks through the hierarchical self-assembly of perylene bisimide (PBI) derivatives represent a significant advancement in supramolecular nanotechnology. In this study, we systematically explored how varying functional groups on the PBI core—specifically propanol, ester, and amide—dictates the resulting nanoarchitecture at the liquid-solid interface. The investigation was conducted using scanning tunneling microscopy (STM) combined with density functional theory (DFT) calculations to elucidate the underlying interaction mechanisms.
When PBI-1, bearing a propanol group, was deposited on freshly cleaved highly oriented pyrolytic graphite (HOPG), it formed linear arrays aligned along specific crystallographic directions. High-resolution STM images revealed alternating bright spots corresponding to the imide nitrogen and perylene ring regions, indicating a non-parallel orientation relative to the substrate. The unit cell parameters were measured as a₁ = 2.4 ± 0.1 nm, b₁ = 4.5 ± 0.1 nm, and γ₁ = 44 ± 1°, consistent with hydrogen bonding between hydroxyl groups on adjacent molecules. DFT simulations confirmed that the tilt angle arises from a balance between intermolecular H-bonding and van der Waals interactions with the surface, supporting the observed ridge-like morphology.
In PBI-2, where a carboxylic acid-containing dendron was attached via ester linkage, the molecular structure promoted dimer formation. The primary driving force was CH···O=C hydrogen bonding between aromatic protons and the carbonyl oxygen of the ester group. These dimers arranged into a parallelogram-shaped 2D network with a₂ = 3.0 ± 0.1 nm, b₂ = 3.1 ± 0.1 nm, and γ₂ = 70 ± 1°. Interdigitated alkyl chains filled the gaps between the dimer rows, providing lateral stability and enhancing the overall coherence of the network. This result highlights the role of both directional hydrogen bonds and steric bulk in guiding assembly.
The most striking transformation occurred in PBI-3, where the ester group was replaced by an amide. The additional N–H bond introduced a second hydrogen-bonding site, enabling the formation of trimers stabilized by three CH···O=C–N hydrogen bonds at the primary level. At the secondary level, six such trimers assembled into a hexagonal ring via six CO···H–N hydrogen bonds. This hierarchical organization led to a large, ordered porous network with a₃ = b₃ = 9.8 ± 0.1 nm and γ₃ = 121 ± 1°. The symmetry and regularity of this structure were unprecedented among PBI-based systems reported previously.
Solvent effects further revealed the robustness and sensitivity of these interactions.NLRP3 Antibody In Vivo When heptanoic acid—a protic, polar solvent—was used instead of 1-phenyloctane, it disrupted the trimeric units in PBI-3 by competing for hydrogen-bonding sites. Instead, a dense dimeric structure resembling PBI-2 emerged, confirming that the amide-based network is highly sensitive to competitive solvation. DFT calculations showed that the interaction energy between heptanoic acid and PBI-3 exceeded that of the CH···O=C–N bond, explaining the structural collapse.CD227 Antibody Epigenetic Reader Domain
Concentration-dependent behavior was also observed.PMID:35185576 Diluting the PBI-3 solution resulted in co-edged hexagons, where each trimer shared hydrogen bonds with three neighbors, reducing the unit cell size to a₅ = b₅ = 6.1 ± 0.1 nm. This transition reflects a shift from isolated pores to interconnected frameworks driven by increased hydrogen-bonding efficiency at lower coverage. Upon evaporation, the system reverted to isolated hexagons, demonstrating dynamic reversibility.
DFT analysis confirmed that the high-concentration PBI-3-high structure exhibits greater thermodynamic stability, with a total energy per unit area of -0.246 kcal mol⁻¹ Å⁻² compared to -0.234 kcal mol⁻¹ Å⁻² for PBI-3-low. The enhanced stability stems from stronger intermolecular hydrogen bonding and more favorable surface interactions.
Finally, the host-guest capability of the hexagonal pores was demonstrated by incorporating coronene (COR). The guest molecule inserted into the cavity without disrupting the framework, forming a stable co-assembled structure with unchanged lattice parameters. DFT calculations verified that the PBI-3-high/COR system has lower energy than the pure PBI-3 network, proving successful stabilization via π–π stacking and van der Waals forces.
This work establishes a powerful strategy for engineering functional 2D molecular networks through targeted modification of PBI derivatives. By controlling hydrogen-bonding motifs and concentration, precise spatial organization can be achieved, offering new pathways for designing advanced supramolecular materials with applications in sensing, catalysis, and molecular electronics.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com