Gas-phase geometry-optimized structures of aspartate complexes of anionic species (Hasp − ) with lithium, sodium and potassium metal cations and transition-state structures for their interconversions were obtained using the density functional theory computations at the B3LYP/6-311++G(d,p) level of theory. The metal ion affinities of Hasp − species and deprotonation energies of [Hasp-M] complexes, M=Li + , Na + and K + , and their conformers were obtained. Relative energies of the [Hasp-M] complex conformers, reaction energies, thermodynamic properties, rate and equilibrium constants of their complexation are reported. Binding energies of the most stable complexes with Li + , Na + and K + are −168.53, −133.34 and −117.68kcal/mol, respectively. The most stable complex conformer as a tri-coordinated form for aspartate complex with Li + and bi-coordinated form for aspartate complexes with Na + and K + were found.