Abstract: 132 stable complexes formed by metal ions(Na+，K+，Ca2+，Mg2+) and fourteen stable adenine tautomers in gas and aqueous phases were optimized at the B3LYP/6-311++G**//6-31+G* level in combination with the PCM models. By comparison, the stabilization ordering of all these stable complexes in aqueous phase is first obtained and the optimal binding site for a metal ion in a specific adenine tautomer is identified. Meanwhile, the differences of the ordering in the two different phases are analyzed systematically. Results indicate that it is solvent effect to induce different solute-solvent interaction and, as a result, lead to the stabilization ordering change from that in gas phase. It is the different metal ion effect to result in the different ordering of relative stability of a complex formed by different metal ion and identical adenine tautomer. For these changes, this article makes detailed analysis based on gas-phase binding energies (EBE) and aqueous phase polarized solute-solvent energies (Epol).

Key words: B3LYP, PCM model, Adenine-M+/2+, Relative stability