Selenourea-Ca2+ Reactions in Gas Phase. Similarities and Dissimilarities with Urea and Thiourea

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• 作者：Cristina Trujillo ; Otilia Mó ; Manuel Y&aacute ; ñ ; ez ; Jeanine Tortajada ; Jean-Yves Salpin
• 刊名：Journal of Physical Chemistry B
• 出版年：2008
• 出版时间：May 1, 2008
• 年：2008
• 卷：112
• 期：17
• 页码：5479 - 5486
• 全文大小：425K
• 年卷期：v.112,no.17(May 1, 2008)
• ISSN：1520-5207

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.