Determine the Relative Aromaticity of Bilayer Graphyne, Bilayer Graphdiyne, and Bilayer Graphtriyne.

The electronic structure characteristics of bilayer graphyne, bilayer graphdiyne, and bilayer graphtriyne were systematically studied using molecular orbital (MO) analysis, density of states (DOS), and interaction region indicator (IRI) methods. The delocalization characteristics of the out-of-plane and in-plane π electrons (i.e., π and π electrons) of these materials were analyzed using the localized orbital locator (LOL). In addition, their responses to external magnetic fields were investigated through anisotropic induced current density (AICD) and isoscalar chemical shielding surfaces (ICSSs) to compare the induced ring currents and magnetic shielding effects, further exploring the aromaticity of the three bilayer materials. The research results indicate that as the number of alkyne groups increases, the aromaticity of the bilayer graphyne structure gradually weakens. Finally, their photophysical properties were studied through TD-DFT calculations. The results show that they exhibit strong localized excitation characteristics.