Cyclo[48]carbon—Evaluation of Its Inherent Magnetic Behavior and Anisotropy from DFT Calculations

Cyclo[48]carbon (C48) exhibits an aesthetically pleasant structure featuring a cyclic polyyne, and it serves as a prototypical medium-sized ring that moves us towards an understanding of its overall magnetic behavior in a challenging molecular shape through analysis of its induced magnetic field. The isotropic induced magnetic field (NICS) profile shows a strong deshielding region at the ring center and a shielding region near the carbon rim, indicating antiaromatic behavior. Under a perpendicular magnetic field, a pronounced deshielding cone extends from the ring center, whereas a parallel external field induces a localized shielding near the carbon backbone. This results in significant magnetic anisotropy above and below the ring plane, characteristic of its medium-sized cyclic structure. Decomposition of the magnetic shielding highlights that paramagnetic effects predominantly govern the magnetic response and anisotropy of C48, with diamagnetic contributions playing a minor role. These insights suggest that chemical modifications targeting frontier orbitals could effectively tune the magnetic properties of cyclo[48]carbon, providing a foundation for the design of substituted derivatives with tailored diamagnetic anisotropy for advanced material applications.