Geometries, stability and aromaticity of Al2P22-, [M(Al2P2)]− (M = Li, Na, K, Cu) and N(Al2P2) (N = Be, Mg, Ca, Zn) clusters

Geometrical structure, aromaticity and other properties of Al2P22-, [M(Al2P2)]− (M = Li, Na, K, Cu) and N(Al2P2) (N = Be, Mg, Ca, Zn) species are theoretically investigated with density functional theory (DFT) methods. Calculation results show that for Al2P22- species, the planar structure, with D2h symmetry at the 1Ag state, is the global minimum at the B3LYP/6-311+G∗ level. Natural bond orbital (NBO) analysis indicates the existence of delocalization in the most stable Al2P22- species and its pyramidal complexes. Nucleus-independent chemical shift (NICS) and molecular orbital (MO) analysis further reveal that that pyramidal [M(Al2P2)]− and N(Al2P2) species preserve the aromatic nature of the most stable Al2P22- unit.