Structure and stability of the heteroannulated [8&ndash;10]circulenes: A quantum-chemical study

Gribanova, Tatyana N.; Zefirov, Nikolay S.; Minkin, Vladimir I.

doi:10.1351/PAC-CON-09-10-36

Pure Appl. Chem., 2010, Vol. 82, No. 4, pp. 1011-1024

http://dx.doi.org/10.1351/PAC-CON-09-10-36

Published online 2010-03-19

Structure and stability of the heteroannulated [8–10]circulenes: A quantum-chemical study

Tatyana N. Gribanova¹, Nikolay S. Zefirov² and Vladimir I. Minkin¹*

¹ Institute of Physical and Organic Chemistry at Southern Federal University, pr. Stachki 194/2, Rostov-on-Don, 344090, Russian Federation
² Moscow State University, Leninskiye Gory, Moscow, 119899, Russian Federation

Abstract: The structure and stability of a new family of heterocyclic [n]circulenes C_nN_nY_n (n = 8–10; Y = N, P, As, BF₂, AlF₂, GaF₂) have been computationally studied using density functional theory (DFT) B3LYP/6-311G* calculations. The geometry of the compounds is determined by the balance of steric factors and effects of aromatic π-electron delocalization depending on the electronegativity of heteroatoms. An increase in the bulkiness of peripheral atoms Y and enlargement of the inner C_n cycle leads to the gradual transformation of the bowl-shaped circulene structure (Y = N, BF₂) to planar and then saddle-shaped forms (Y = P, As, AlF₂, GaF₂). The calculations performed manifest stabilization of the heteroannulated circulenes ensured by the strong aromatic character of the conjugated five-membered rings fringing the central non-aromatic or antiaromatic [8–10] annulene rings.