Exploring the geometrical structures of X©BnHnm [(X, m) = (B, +1), (C, +2) for n = 5; (X, m) = (Be, 0), (B, +1) for n = 6] by an electronic method.

A series of singlet and triplet wheel-type clusters obtained through an electronic method, i.e., adding two and four electrons into X©BnHnm [(X, m) = (B, +1), (C, +2) for n = 5; (X, m) = (Be, 0), (B, +1) for n = 6], have been studied theoretically. With the increase of the number of electrons, the sizes of peripheral boron rings tend to decrease due to the increase of negative charges on the boron rings. The results of the kinetic stability and the electronic stability suggest that the triplet C©B5H5 and singlet Be©B6H6 are stable and may be detected experimentally. Nucleus-independent chemical shift and molecular orbital analysis reveal that some wheel-type clusters with the planar ring possess aromaticity properties that are attributed to the delocalized π electrons conforming to the Huckel rule, i.e. 4n + 2 for singlets or 4n for triplets. These findings from this work are significant for designing novel wheel-type clusters. [ABSTRACT FROM AUTHOR]