BN Substituted Non-Classical Fullerenes

The non-classical fullerenes containing other kinds of polygons, such as square or heptagonrings, are within the range of energies spanned by the classical fullerene isomers and may be thecompetitors of classical fullerenes [1]. Among non-classical fullerenes, we have chosen the C46and C62 with one square ring and C32 with two square rings to investigate the electronic andmagnetic properties of BN substituted non-classical fullerenes, which are fully optimized at theM06-2X/6-311G level. Complete BN substitution of one of the square rings will make a C2-symmetric heterofullerene (C58B2N2, C42B2N2, and C28B2N2). Further BN substitution of thecarbon atoms is continued until complete BN substitution of one of the[4] radialene-like structure(C54B4N4, C38B4N4, and C24B4N4). The binding energies of BN substituted non-classicalfullerenes are slightly smaller than those obtained for non-classical fullerenes [2]. The IRspectrum in the BN substituted heterofullerenes are similar to those of their parents because oflow concentration of B-N impurity, separated into two regions: the stronger absorptions at 1200-1400 cm-1 driven from the stretching of C-B, C-N, B-N, and C-C bonds, while the weakerabsorptions at 600-800 cm-1 corresponding to the out-of-plane bending and breathing modes.NICS value in the cage center of C62 is obtained to be -7.05, which is close to that reported forC60. In fact, C62 contains diatropic hexagons and paratropic pentagons with NICS values of -6.6and +6.9 at the ring centers, respectively. NICS value of C32 is obtained to be -35.3 which is verysimilar to that reported for the classical C36 fullerene [3]. The compensation between diatropicand paratropic ring currents yields a more negative NICS values in the corresponding BNsubstituted fullerenes than in C62. The similar ring currents combine to produce non-aromaticcharacter at the center of the BN substituted C46 fullerene. On the other hand, BN-doping affectsaromaticity of the whole rings in the C32, leading to decrease of the aromatic character ofC28(BN)2 and C24(BN)4 in comparison to their parents.

Keywords:

Non-Classical Fullerenes , Aromaticity , DFT , NICS