Influence of External Electric Field on B₆C₆N₆: Focusing on Structure, Electronic Structure, Spectra and Reactivity

Ternary B₆C₆N₆ monocyclic compounds remain purely theoretical, with no experimental synthesis reported, and their behavior under external electric fields (EEFs) is largely unexplored. Taking the D_3h-symmetric B₆C₆N₆ isomer as a model, EEF-induced changes in geometry, bonding, electronic structure, excited-state properties, and reactivity were calculated at the ωB97XD/def2-TZVP level combined with TD-DFT (time-dependent density functional theory) and wavefunction analyses. As the EEF strength increases from 0 to 0.029 a.u. (-F_y direction), B₆C₆N₆ undergoes a regular D_3h→C_2ν symmetry reduction, with the N10-N15 bond at -F_y EEF source elongated from 1.28 Å to 1.46 Å, the cavity diameter contracted from 4.065 to 1.201 Å, and the long axis length expanded from 7.631 Å to 9.843 Å, and charge displacement reaches 0.88 e at -0.029 a.u. The HOMO-LUMO gap narrows from 7.81 eV to 5.03 eV, and the lowest-energy absorption band red-shifts from 316.3 nm to 679.8 nm, with a transition from local to charge-transfer excitation. OWDD (orbital-weighted dual descriptor) and LEAE (local electron attachment energy) analyses imply that -F_y EEF spatially reshapes the reactive sites, with the LEAE value at preferred nucleophilic sites decreasing to -7.07 eV at -0.029 a.u. These results provide a theoretical basis for understanding and potentially regulating B₆C₆N₆ isomers via EEFs.