Magnetically induced current densities and current pathways have been calculated for a series of fully annelated dicationic and dianionic tetraphenylenes, which are also named circulenes. The gauge including magnetically induced current (GIMIC) method has been employed for calculating the current density susceptibilities. The aromatic character and current pathways are deduced from the calculated current density susceptibilities showing that the neutral circulenes have two concentric pathways with aromatic and antiaromatic character, respectively. The inner octatetraene core (the hub) is found to sustain a paratropic (antiaromatic) ring current, whereas the ring current along the outer part of the macrocycle (the rim) is diatropic (aromatic). The neutral circulenes can be considered nonaromatic, because the sum of the ring-current strengths of the hub and the rim almost vanishes. The aromatic character of the doubly charged circulenes is completely different: the dianionic circulenes and the OC-, CH-, CH2-, SiH-, GeH-, SiH2-, and GeH2-containing dicationic species sustain net diatropic ring currents i.e., they are aromatic, whereas the O-, S-, Se-, NH-, PH- and AsH-containing dicationic circulenes are strongly antiaromatic. The present study also shows that GIMIC calculations on the circulenes provide more accurate information about the aromatic character than that obtained using local indices such as nuclear-independent chemical shifts (NICSs) and H-1 NMR chemical shifts.
1.KTH Royal Inst Technol, Sch Biotechnol, Div Theoret Chem & Biol, S-10691 Stockholm, Sweden 2.Bohdan Khmelnitsky Natl Univ, Dept Organ Chem, Blvd Shevchenko 81, UA-18031 Cherkassy, Ukraine 3.Tomsk Polytech Univ, 30 Lenin Ave, Tomsk 634050, Russia 4.Tomsk State Univ, 36 Lenin Ave, Tomsk 634050, Russia 5.Univ Helsinki, Dept Chem, POB 55 AI Virtanens Plats 1, FIN-00014 Helsinki, Finland 6.Chinese Acad Sci, Inst Chem, Key Lab Engn Plast, Beijing 100190, Peoples R China 7.Chinese Acad Sci, Inst Chem, Beijing Natl Lab Mol Sci, Beijing 100190, Peoples R China