How does an external electric field in the normal-direction affect the cyclo[18]carbon molecule?—a DFT study

This investigation explores the impact of an external electric field (EEF) in the normal-direction on cyclo[18]carbon, scrutinizing changes in molecular conformation, electronic structure, reactivity, and spectroscopic properties. Utilizing Gaussian16 and Multiwfn, we modeled the molecule under EEF conditions. The EEF induced an expansion of the cyclo[18]carbon ring and increased bond lengths. Interestingly, as the EEF strength increased, the molecular dipole moment showed a clear linear growth trend. Electronic structure and conceptual density functional theory (CDFT) analyses indicated a reduced HOMO-LUMO gap, enhancing chemical reactivity, and a shift in reactive sites. Spectroscopic data revealed new peaks in the infrared spectrum and a redshift in the ultraviolet-visible spectrum due to the EEF. Additionally, the EEF regulated the interplanar distance and binding energy of the cyclo[18]carbon dimers, influencing π-π stacking interactions. These findings underscore the significance of EEF directionality and intensity in modulating molecular characteristics, laying a theoretical groundwork for future studies on the response of cyclo[18]carbon to EEFs.