PHOTOELECTRON-SPECTROSCOPY OF DOUBLY-CHARGED ANIONS - INTRAMOLECULAR COULOMB REPULSION AND SOLVENT STABILIZATION

Photoelectron spectroscopy has been combined with an electrospray ioni zation technique to study gas-phase multiply charged anions and their intramolecular Coulomb repulsion and solvation stabilization. We repor t an initial study on a series of linear dicarboxylate dianions (DC2-) , -O2C(CH2)(n)CO2- (n = 3-6), solvated by one and two waters. The seco nd electron binding energy of DC2- decreases with decreasing aliphatic chain length owing to the increasing Coulomb repulsion between the tw o charges; the dianion with n = 2 has a binding energy close to zero a nd is not stable in the gas phase. We found that this dianion can be s tabilized by one water, and in general the first water stabilizes the electron binding energy of DC2- by similar to 0.3 eV. The second water , however, was observed to show a much stronger stabilization effect ( similar to 0.6 eV), suggesting that the two waters solvate the two car boxylate groups separately.