B3LYP/6-31G* calculations show that the most stable structures of C48B12 and C48N12 can still be considered as acceptor and donor, respectively. The rectifier property, however, whose typical characteristic is the energy difference between acceptor, lowest unoccupied molecular orbital (LUMO) and the donor, highest unoccupied molecular orbital (HOMO) level is calculated to be 0.82 eV, several order of magnitude larger than the 0.14 eV value calculated recently for less stable isomers at the same level of theory. This requires the application of a much larger voltage bias for the C48B12 and C48N12 pair to be considered as valid components in molecular electronics. (C) 2003 Elsevier B.V. All rights reserved.