AB-INITIO STUDIES OF PEROXYNITRITE ANION-WATER COMPLEXES

Quantum mechanical methods have been applied to the cis-ONOO--H2O, cis -ONOO--(H2O)(2) and trans-ONOO--H2O complexes. Equilibrium geometries, binding energies, net atomic charges and vibrational frequencies are presented for several different arrangements. The Moller-Plessett seco nd-order perturbation (MP2) method predicted shorter hydrogen bonds th an the SCF method, but the computed Hartree-Fock (HF) binding energies are similar to counterpoise corrected MP2 values. The geometry change s of ONOO- and water after solvation are examined. The ONOO- and H2O b ond length changes follow typical hydrogen bond structural trends, whe reas bond angles in ONOO- are unaffected when the hydrogen bond is for med, similar to the conclusions from NO2--(H2O)(n) HF/6-31G studies an d Monte Carlo simulations. The cis-ONOO--(H2O)(n) frequencies are comp ared with the solution Raman spectrum and with calculations on isolate d ONOO-.