Theoretical insight into the doubly antiaromatic carbon allotrope cyclo[16]carbon.

A new carbon allotrope, cyclo[16]carbon (C 16 ), has recently been successfully synthesized. It is hypothesized to exhibit double antiaromatic properties owing to the 4 n π electrons. Theoretical calculations are a feasible method for systematically studying the structures and properties of unstable antiaromatic molecules. The results show that C 16 has a planar structure characterized by alternating long and short bonds with D 8h , and a strong antiaromatic characteristic originates from the two perpendicular π systems. We performed an extensive comparative analysis of C 16 and the aromatic cyclo[18]carbon, C 18 . This study offers valuable insight into the structural and electronic characteristics of C 16 and could inspire innovative applications and avenues for its utilization in various fields.