Accurate ab initio G1 and G2 protocols have been used to characterize 14 [GRAPHICS] with n = 1-4, species. We have predicted that the C-site protonation of the earlier characterized [GRAPHICS] (B-2(1)) species is preferred over the P-site by 1.73 eV at the G2 level. For the [GRAPHICS] system, five stable molecular structures have been found fur each of the singlet and triplet spin multiplicities. In particular, the [GRAPHICS] singlet isomers du not present either biradicaloid character or P-C cross bonding, while both the [GRAPHICS] and [GRAPHICS] singlet molecules are almost pure biradical species with no P-C cross bonding. For every case the singlet state has been found to be more stable than the triplet. Finally, vibrational spectra of these species, which may help in their detection, are discussed.