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 D3h-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. (−Fy direction), B6C6N6 undergoes a regular D3h→C2ν symmetry reduction, with the N10–N15 bond at −Fy 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 −Fy 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.