OPEN-CHAIN AND CYCLIC PROTONATED OZONE - THE GROUND-STATE POTENTIAL-ENERGY HYPERSURFACE

Theoretical studies have been performed in an attempt to elucidate the intricate potential-energy hypersurface of protonated ozone(HO3+). Protonation of both open-chain (C2v) and cyclic (D3h) forms of ozone (O3) has been investigated. Methods used involved self-consistent-field (SCF) and coupled cluster including all single and double substitutions (CCSD) geometry optimizations utilizing a double-zeta plus polarization (DZ+P) basis. Harmonic vibrational frequencies have been predicted at the SCF level in order to characterize the stationary points obtained. In addition, single and double excitation configuration interaction (CISD) and CISD+Q single-point energies were determined for all stationary points. The global minimum for HO3+ was found to be a terminally attached proton on open-chain ozone in a trans arrangement, with the corresponding cis isomer 3.6 kcal mol-1 higher in energy. Protonation of ozone does not preferentially stabilize the cyclic isomer relative to the open-chain form.