Structures and Dynamics of Negatively-Charged Molecular Clusters

In the present study，we have concentrated our attention to(1)the geometrical and electronic structures and(2)reactivities of negatively-charged molecular clusters：(1)The electronic structures of[(CO_2)_nROH]^-(R=H，CH_3，and C_2H_5)were investigated by photoelectron spectroscopy.The analysis of the spectra revealed that two forms of isomers coexist in[(CO_2)_nROH]^-(2*n*3)；one has an electronic structure described as[C_2O_4^-·ROH(CO_2)_&lt；n-2&gt；]where the excess electron is delocalized over two CO_2molecules，and the other involves a monomer anionic core as[CO_2^-·ROH(CO_2)_&lt；n-1&gt；]。This is one of the few experimental rasults which demonstrates the coexistence of isomers of negatively-charged molecular clusters having defferent electronic structures.The present findings are also supported byab initio calculations at the unrestricted Hatree-Fock levels.(2)New type of gas-phase reactions involving nagatively-charged molecular clusters were investigated by mass spectrometric technique combined with photoelectron spectroscopy.For example，we have reported reactions of(CO_2)_n^-with CH_3I leading to the formation of a novel molecular anion[CO_2CH_3I]^-，which has not been observed in the corresponding condensed-phase reaction.It turned out that[CO_2CH_3I]^-has a large vertical detachment energy，implyintg that the excess electron is delocalized over[CO_2CH_3I]^-to form an acetate-iodine complex[CH_3CO_2-I]^-.This suggests that(CO_2)_n^-reacts with CH_3I via anucleophilic process.Ab initio calculations are under way to get information on the geometrical and electronic structures of[CO_2CH_3I]^-.

In the present study, we have concentrated our attention to (1) the geometrical and electronic structures and (2) reactivities of negatively-charged molecular clusters :(1) The electronic structures of [(CO_2)_nROH]^-(R=H,CH_3, and C_2H_5) were investigated by photoelectron spectroscopy. The analysis of the spectra revealed that two forms of isomers coexist in [(CO_2)_nROH]^-(2*n*3) ; one has an electronic structure described as [C_2O_4^-・ROH(CO_2)_<n-2>]where the excess electron is delocalized over two CO_2 molecules, and the other involves a monomer anionic core as [CO_2^-・ROH(CO_2)_<n-1>]. This is one of the few experimental rasults which demonstrates the coexistence of isomers of negatively-charged molecular clusters having defferent electronic structures. The present findings are also supported byab initio calculations at the unrestricted Hatree-Fock levels.(2) New type of gas-phase reactions involving nagatively-charged molecular clusters were investigated by mass spectrometric technique combined with photoelectron spectroscopy. For example, we have reported reactions of (CO_2)_n^-with CH_3I leading to the formation of a novel molecular anion [CO_2CH_3I]^-, which has not been observed in the corresponding condensed-phase reaction. It turned out that [CO_2CH_3I]^-has a large vertical detachment energy, implyintg that the excess electron is delocalized over [CO_2CH_3I]^-to form an acetate-iodine complex [CH_3CO_2-I]^-. This suggests that (CO_2)_n^-reacts with CH_3I via anucleophilic process. Ab initio calculations are under way to get information on the geometrical and electronic structures of [CO_2CH_3I]^-.