Study on the Induced Dipole Moment of Cyclo[18]Carbon under EEFs

This study systematically investigates the variation of the induced dipole moment of the cyclo[18]carbon molecule under external electric field (EEF) applied along different axes using quantum chemical calculations. The results show that under an EEF applied along the z-axis (normal to the molecular plane), the induced dipole moment of the cyclo[18]carbon molecule exhibits a significant linear relationship with the EEF strength. In contrast, under an EEF applied along the x-axis (parallel to the molecular plane), the linear relationship is gradually disrupted as the EEF strength increases, and the cyclo[18]carbon molecule exhibits a significantly higher response to the x-axis EEF than to the z-axis EEF. Further electronic structure analysis reveals that the high responsiveness along the x-axis is attributed to the high delocalization of π-electrons in the cyclo[18]carbon molecule along this direction. By decomposing the induced dipole moment into electronic displacement dipole moments and geometric configuration dipole moments, it is found that the contribution of the geometric configuration dipole moment under x-axis EEFs is the primary cause of the deviation of the total induced dipole moment from the linear relationship. This study not only deepens the understanding of the behavior of the cyclo[18]carbon molecule in EEFs but also provides theoretical insights for the design of molecular electronic devices and the study of chemical reaction mechanisms in EEFs.