Several complexes of alumaphosphinine ring with cations (Li+, Na+, K+, Be2+, Mg2+, and Ca2+) were optimized at B3LYP/6-311++G(d,p), and the single-point calculations were performed at MP2/6-311++G(d,p) level of theory. Different aspects of cation- interaction, including interaction energy calculations, charge transfer values, and the variations in aromaticity of the ring upon complexation, were also considered. Natural Bond Orbital (NBO) analysis was performed to calculate the charge transfer and natural population analysis of the complexes. Quantum Theory of Atoms In Molecules (QTAIM) was also applied to analyze the properties of the bond critical points in the complexes. Finally, Nucleus Independent Chemical Shift (NICS), the Harmonic Oscillator Model of Aromaticity (HOMA), the Para-Delocalization Index (PDI), and the aromatic  fluctuation
index (FLU) were applied to evaluate the variation of aromaticity of the alumaphosphinine ring induced upon complexation.