Abstract: Eleven stable adenine-Zn2+ isomers in aqueous phase were investigated at B3LYP/6-311++G** level in combination with the PCMand Onsager models. Different from those in gas phase, the stabilization ordering of these adenine-Zn2+ isomers in the aqueous phase changed and the binding sites of Zn2+ showed obvious regularity. In the adenine-Zn2+ isomerswith imine group, the complexeswith the combination between Zn2+ and (N7 andN6 ) sitesweremore stable than those with the combination between the Zn2+ and (N1 and N6) sites. In those isomers with amido groups, the preferred ordering of double nitrogen sites for Zn2+ combination was (N3 and N9)>(N7 and N6)>(N1 and N6). Activation energy calculations indicated that the intramolecular proton transfer (i.e., (N6)Ha→Ha(N1) in a9=>a9→a19l) was difficult for an isolated adenine (a9). Moreover, Zn2+ could hardly induce the decrease of activation energy of intramolecular proton transfer both in the gas and aqueous phases, whereas the Cu2+ could and the effect was obvious.

Key words: Ademine-Zn2+ isomers, Stability, DFT, Proton transfer, PCMmodel, Onsager model