Stabilization of the adenine covalent anion by micro-hydration: theoretical study

The Rydberg electron–transfer spectroscopy (RET) experiment [V. Periquet, A. Moreau, S. Carles, J.P. Schermann, C. Desfrançois, J. Electron. Spectrosc. Relat. Phenom., 106, 141 (2000)] showed that only after solvation by two water molecules the adenine molecule can form a stable covalent anion. Anions of adenine–water complexes containing different numbers of water molecules (A·W n , n =1–4) are investigated in this work with the use of quantum mechanical ab initio calculations. The calculations are used to determine the change of stability of the adenine covalent anion as the number of water molecules in the solvation shell increases. The analysis of the anion electron density is used to describe the localization of the excess electron in the A·W n complexes.