Unimolecular reactivity of the [urea-Sr]²⁺ complex, a metastable dication in the gas phase. An experimental and theoretical perspective

Ane Eizaguirre (1) , Otilia Mó (1) , Manuel Yáñez (1) , Jeanine Tortajada (2) , Jean-Yves Salpin (2)

1 Departemento de Química C-9
2 LAMBE - Laboratoire Analyse et Modélisation pour la Biologie et l'Environnement

The interactions between urea and Sr²⁺ in the gas phase have been investigated by combining electrospray ionization/mass spectrometry techniques and density functional and high-level ab initio molecular orbital calculations. Our theoretical survey indicates that [Sr(urea)]²⁺ adducts are thermodynamically stable with respect to direct Coulomb explosions. However, after isomerization, some of the local minima of the PES are thermodynamically unstable with respect to the formation of NH₄⁺, but kinetically metastable. The loss of neutral fragments with the concomitant generation of lighter doubly-charged fragment ions, namely [(H₃N)Sr]²⁺ and [(HNCO)]Sr²⁺, compete with the aforementioned Coulomb explosion processes yielding NH₄⁺ + [(NCO)Sr]⁺ and [(H₂N)Sr]⁺ + [H₂NCO]⁺, although the former processes dominate. Hence, both singly- and doubly-charged species are detected as dissociation products. Quite importantly, the observed eliminations of NH₃ or HNCO, lead to the formation of new doubly-charged species, which turn out to be thermodynamically stable.

Mots clés: Dications; Dissociation products; Former process; Gasphase; Local minimums; Neutral fragments; Spectrometry technique; Thermodynamically stable; Unimolecular; Metabolism; Density functionals; Calculations; Dielectric devices; Gases; Orbital calculations; Urea; Ab initio molecular orbital calculation; Charged fragments; Charged species; Coulomb explosion; Coulomb explosion process

Domaines: Chimie-Physique [physics.chem-ph]

Ane Eizaguirre, Otilia Mó, Manuel Yáñez, Jeanine Tortajada, Jean-Yves Salpin. Unimolecular reactivity of the [urea-Sr]²⁺ complex, a metastable dication in the gas phase. An experimental and theoretical perspective. Journal of Physical Chemistry B, 2013, 117 (7), pp.2088-2095. ⟨10.1021/jp312466t⟩. ⟨hal-00912477⟩