Adenine-hydrogen peroxide system: DFT and MP2 investigation

Theoretical calculations have been performed for different possible hydroge n bonding complexes between adenine and hydrogen peroxide (AHP). The studie d complexes (1-6) were cyclic ones showing two hydrogen bonds of different strength. All of the structures have been characterized at the B3LYP/6-31G( 2d,p) and MP2(full)/6-31G(2d,p) levels, yielding only real frequencies (min ima) at the B3LYP/6-31G(2d,p). The binding energies have been carried out f or all of the structures, taking into account the so-called BSSE and yieldi ng for the most stable structure 6 values of -11.53 and -11.95 kcal/mol at the B3LYP and MP2 levels, respectively. BSSE-free PES calculations were als o performed for several complexes. The Bader analyses were also applied to investigate the hydrogen bonding electronic properties.