Carbon-nitrogen nanorings and nanoribbons: a theoretical approach for altering the ground states of cyclacenes and polyacenes.

Carbon-nitrogen nanorings with formulae (CN) and in the form of [ n]pyrazine cyclacenes appear either as closed-shell singlets (S) for n = 5, 10, and 12, or open-shell singlets (S) for n = 6, 7, 9, and 11 at restricted and unrestricted broken spin-symmetry density functional theory (DFT). All of their corresponding acyclic isomers, which are called [ n]pyrazine polyacenes or nanoribbons, appear as S for n = 5-12. As a result, nitrogen substitutions alter the electronic ground state of cyclacenes and polyacenes and appear to increase their viability, which invites further experimental and theoretical realization and exploration. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]