Study on electronic structure and excitation characteristics of cyclo [18] carbon

The omega B97XD/def-TZVP method based on DFT was used to optimize the structure of C-18. Then based on the TD-DFT omega B97XD/aug-cc-PVTZ method, the first 50 excited states were calculated in the gas phase. The Mayer bond order, UV spectrum, electron-hole distribution and LOL were calculated. The results showed that the C-C bond length and Mayer bond order show alternating features. UV spectrum is mainly formed by the ground state transition to the 21st, 22nd, 39th and 40th excited states, and the four excitations are local excitations. The Trelectrons in the upper and lower planes of the molecular plane have high delocalization.