文摘
The gas-phase reactions between Ca2+ and selenourea were investigated by means of electrospray/tandemmass spectrometry techniques. The MS/MS spectra of [Ca(selenourea)]2+ complexes show intense peaks atm/z 43, 121, 124, and 146 and assigned to monocations produced in different coulomb explosion processes.The structures and bonding characteristics of the stationary points of the [Ca(selenourea)]2+ potential energysurface (PES) were theoretically studied by DFT calculations carried out at the B3LYP/6-311+G(3df,2p)//B3LYP/6-311+G(d,p) level. The analysis of the topology of this PES allows identification of H2NCNH+,CaSeH+, selenourea+· and CaNCSe+ ion peaks at m/z 43, 121, 124, and 146, respectively. The reactivity ofselenourea and the topology of the corresponding potential energy surface mimic that of thiourea. However,significant dissimilarities are found with respect to urea. The dissociative electron-transfer processes, notobserved for urea, is one of the dominant fragmentations for selenourea, reflecting its much lower ionizationenergy. Similarly, the coulomb explosions yielding CaXH+ + H2NCNH+ (X = O or Se), which for urea arenot observed, are very favorable for selenourea. Finally, while in urea the loss of NH3 competes with theformation of NH4+, for selenourea the latter process is clearly dominant.
