Analysis of the aromaticity in extended systems formed from isoelectronic Al₄ ²⁻ and C₄ ²⁺ aromatic clusters

Inspired by carbo-benzene and its inorganic analogues, in the current work, the viability of extended systems (called carbomers) formed from aromatic small rings was studied. The aluminum aromatic cluster, Al₄ ²⁻, and its isoelectronic carbon analogue, C₄ ²⁺, were employed as starting point. The insertion of alkynyl units into the Al–Al and C–C bonds results in the extended molecules named carbomers. These molecules were compared with the global minima structures, which were searched employing the genetic algorithm program, GEGA. The electronic delocalization (aromaticity) of the isomers was studied with the induced magnetic field (B^ind). The results showed that global minimum of C₁₂ ²⁺ (formed from C₄ ²⁺) was an unexpected diatropic structure which presented a similar magnetic response to the C₄ ²⁺ cluster. Also, optical properties of C₁₂ ²⁺ were computed.