Electronic and structural properties of fractal coronene derivatives: A DFT study

This study presents a comprehensive theoretical investigation of the electronic and structural properties of a series of fractal molecular architectures derived from benzene and progressively extended toward circumcoronene-like graphene analogues. Molecular geometries were constructed using GaussView 6, while all quantum-chemical calculations were carried out within the Gaussian 09 package using density functional theory (DFT) at the B3LYP/6-31G level, ensuring a reliable balance between computational accuracy and efficiency. The gradual expansion of the hexagonal framework resulted in a systematic reduction in the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), indicating enhanced electronic delocalization and improved charge-transport characteristics in higher-order fractal structures. Electron density contour maps revealed an increased π-electron symmetry in the central regions of the larger systems, whereas smaller units exhibited an edge-localized electron density, consistent with the development of extended π–π conjugation. In addition, the density of states (DOS) spectra demonstrated a pronounced broadening of both occupied and virtual states with an increasing structural size, confirming the strong correlation between the fractal growth and electronic transport behavior. Furthermore, analysis of the HOMO and LUMO distributions showed an orbital broadening and enhanced spatial symmetry in advanced fractal geometries, accounting for the observed reduction in the energy gap. These results indicate that coronene-based fractal structures exhibit significant potential for applications in conductive nanomaterials and molecular electronics, as their electronic and structural properties can be finely tuned through controlled fractal branching, enabling tailored performance in next-generation nanoscale devices.