Electronic transport in radial π-conjugated macrocyclic molecules: a density functional theory study

Area of Science:

• Organic electronics
• Materials science
• Computational chemistry

Background:

• Radially conjugated macrocyclic molecules enable tuning of frontier orbital energies.
• Donor-acceptor (D-A) interactions and ring geometry are key factors in molecular design.

Purpose of the Study:

• To systematically investigate the electronic structure and metal-molecule energy-level alignment of macrocyclic molecules.
• To establish quantitative structure-property relationships for D-A macrocyclic architectures.

Main Methods:

• Density Functional Theory (DFT) calculations.
• Analysis of electronic structure (HOMO-LUMO gap).
• Modeling of metal-molecule junctions (Au18) to study energy-level alignment.

Main Results:

• Macrocyclization induces system-specific changes in the HOMO-LUMO gap, influenced by ring strain and D-A coupling.
• [DTBDT-DPP]3 exhibits the smallest HOMO-LUMO gap and favorable HOMO alignment with the Au18 Fermi level.
• A low hole injection barrier (Φh ≈ 0.01–0.21 eV) was predicted for [DTBDT-DPP]3, identifying it as a promising candidate.

Conclusions:

• Macrocyclization offers a viable strategy for designing organic semiconductors with tailored electronic properties.
• The study provides a computational framework for rational design of macrocycle-based materials for organic electronics.
• Quantitative structure-property relationships were established for five D-A macrocyclic systems.