1. Introduction A circulene is a fower-type molecule comprising a core and its surrounding petals that has the general formula [n:(p 1 ,p 2 ) n/2 ], where n is the folding of the core polygon and p i are the polygonal petals. For n<6, the molecule is bowl-shaped, whereas for n>6 it is saddle-shaped [1-3]. The bowl-shaped circulenes are potentially useful in the direct synthesis of fullerenes [4,5] while the saddle- shaped circulenes could appear as patches in foamy structures of spongy carbon [6,7]. The idea of increasing aromaticity/stability of fullerenes tessellated by disjoint circulenes/fowers originates in the classical texts of Clar [8,9] that postulated disjoint benzenoid rings (i.e., rings having six π-electrons localized in double-simple alternating bonds and separated from adjacent rings by formal single bonds) as a criterion for the full aromatic conjugation (i.e., double-simple bond alternation) [10]. According to the VB theory, molecular structures exhibiting such fully resonant sextets are expected to be extremely stable [10-12]. Patterns larger than benzene, e.g. naphthalene or azulene (i.e., a pair of pentagon- heptagon carbon rings) have been investigated in the context of the Clar’s theory of aromaticity. By extension [13-16], circulene supra-faces (eventually called fowers) may also be taken into consideration [1,2]. A set of disjoint faces, built up over all atoms of the molecule, is called a perfect Clar PC structure (Fig. 1, middle). Only in polyhex structures, (e.g. polyhex toroids) where the empty/full assignment can be interchanged at two adjacent hexagons, the PC structure consists of full π-electron, disjoint hexagons, as originally suggested by Clar. However, the PC structures in fullerenes include Central European Journal of Chemistry Fullerenes patched by fowers * E-mail: diudea@gmail.com Received 14 August 2012; Accepted 21 November 2012 Abstract: © Versita Sp. z o.o. Keywords: ab initio • HOMA • NICS • Circulenes • Fullerene patches 1 National Institute for Research and Development in Electrochemistry and Condensed Matter, 300569 Timisoara, Romania 2 University “POLITEHNICA” of Timisoara, Faculty of Industrial Chemistry and Environmental Engineering, 300006 Timisoara, Romania 3 Faculty of Chemistry and Chemical Engineering, “Babes-Bolyai” University,400028 Cluj, Romania 4 Department of Physical Chemistry, Collegium Medicum, Nicolaus Copernicus University, 85–950 Bydgoszcz, Poland 5 Institute of Physics, University of Szczecin, 70-451 Szczecin, Poland Raluca Pop 1 , Mihai Medeleanu 2 , Mircea V. Diudea 3* , Beata Szefer 4 , Jerzy Cioslowski 5 Research Article Stability measures, such as the total energy and the HOMO-LUMO gap, calculated at the Hartree-Fock and DFT levels of theory, and the aromatic character of fve circulenes/fowers with a hexagonal core and petals consisting of 5-, 6- and 7-membered rings are investigated. Geometric (HOMA) and magnetic (NICS) criteria are used to estimate the local aromatic character of every ring of the investigated circulenes. The local aromaticity of the coronene and sumanene patches in two tetrahedrally spanned fullerenes were calculated and compared with the HOMA and NICS values of the corresponding isolated circulenes. Cent. Eur. J. Chem. • 11(4) • 2013 • 527-534 DOI: 10.2478/s11532-012-0191-2 527