Modeling Structural and Optical Properties of 6,6,12-Graphyne Oligomer Fragments.

This study investigates the structural and optical properties of 6,6,12-graphyne by analyzing five different radiaannulene oligomer fragments of the two-dimensional (2D) sheet in vacuum, cyclohexane, dichloromethane, and toluene. These properties are examined using various density functional theory (DFT) methods in combination with different basis sets. Solvent effects are incorporated using the integral equation formalism polarizable continuum model (IEF-PCM). The findings indicate that structural properties are primarily influenced by the inclusion of exact Hartree-Fock exchange in the chosen DFT method and the presence of polarization functions in the applied basis sets. For optical properties, all five molecules absorb light across the visible spectrum through both one- and two-photon processes. Notably, the inclusion of range correction in the selected method significantly alters the optical characteristics making alignment with experiment and CC2 (Coupled Cluster with Singles and approximate Doubles) calculations better. The presence of a solvent is found to enhance both infrared and ultraviolet-visible (UV-vis) absorption, while enforcing a planar geometry on the systems has minimal impact on the observed properties. Finally, comparisons with experimental spectra confirm that the calculations accurately reproduce key features and trends in the experimental data.