The topology of the magnetically induced ring current of C₁₃Cl₂

We have performed density functional theory (DFT), second-order Møller-Plesset perturbation theory (MP2), coupled cluster singles and doubles (CCSD), and complete-active-space self-consistent-field (CASSCF) calculations of the magnetically induced current density (MICD) susceptibility of the molecular structures of C₁₃Cl₂ belonging to the C ₂ and C _2v point groups. The ring of the planar C _2v structure of C₁₃Cl₂ is aromatic sustaining a strong diatropic magnetically induced ring current (MIRC) and no paratropic contribution to the MIRC. The paratropic MIRC of the C ₂ structure suggests that it is weakly antiaromatic. Its paratropic MIRC makes several vertical loops around the cumulene part of the ring and passes on the inside of the other half of the ring. The strongest MIRC trajectories have a very unusual topology with a very large linking number (L _k) of 6π, which is the same as we obtained for the helical highest-occupied molecular orbital (HOMO). Our study shows that it is not necessary to introduce the half-Möbius topology concept to understand the electronic structure and the magnetic response of the C ₂ structure of C₁₃Cl₂.