Electronic Structure and Spectral Properties of Radical Heterocyclocarbon C12N Isomers.

Cyclo[n]carbons are reactive ring-shaped carbon allotropes that have been theoretically and experimentally studied for various numbers of carbon atoms in the ring (n). Recently, the first heterocyclocarbon, C12N, was experimentally synthesized and its molecular structure confirmed using scanning tunneling microscopy by Sun et al., revealing a likely C2v-symmetric ring. In this paper, we report on further theoretical investigation on the C12N molecule and its isomers, which have different bond length alternation (BLA): cumulene-like structure with smaller BLA and polyyne-like one with larger BLA. Calculations confirm that the cumulene-like C12N structure is slightly more stable. Calculated BLA, bond angle alternation, isochemical shielding surface, magnetically induced ring current, and g-factor consistently indicate the aromaticity of the cumulene-like C12N and antiaromaticity/less-aromaticity of the polyyne-like C12N. In addition, calculated electron paramagnetic resonance and infrared and Raman spectroscopic data are reported for both isomers as potential features for experimental identification in the future.