Journal of Physical Chemistry B, Vol.117, No.7, 2088-2095, 2013
Unimolecular Reactivity of the [Urea-Sr](2+) Complex, a Metastable Dication in the Gas Phase: An Experimental and Theoretical Perspective
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)-Sri 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.