The electronic structures and ionization potentials of C4O4^m^-(m=0, 1, 2, 3, 4) are calculated at the RHF(UHF)/6-31G, RHF(UHF)6-31G^* and RHF(UHF)6-31+G levels using ab initio SCF and Boys localzed molecular orbital (LMO) approaches. The characteristic of bonding and the relationship between ionization potential and corresponding ΔE~S~C~F are discussed. Vibrational frequencies, IR intensities and intrinsic frequencies and force constants have also been calculated at the 6- 31G level by analytical second derivatives at the optimized equilibrium geomtries. The results of the electronic structures and Boys LMO calculations and the vibrational analyses are consistent with the optimized equilibrium geometries.

Key words: CYCLIC COMPOUNDS, AROMATIC COMPOUNDS, AB INITIO CALCULATION, STRUCTURAL CHEMISTRY, IONIZATION POTENTIAL, FREQUENCY OF VIBRATION, BONDING