Stable doubly charged positive molecular ions formed by direct attachment of alpha particles to HCN and HNC

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 Sr(2+) 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 NH(4)(+), but kinetically metastable. The loss of neutral fragments with the concomitant generation of lighter doubly charged fragment ions, namely, [(H(3)N)Sr](2+) and [(HNCO)]Sr(2+), compete with the aforementioned Coulomb explosion processes yielding NH(4)(+) + [(NCO)Sr](+) and [(H(2)N)Sr](+) + [H(2)NCO](+), although the former processes dominate. Hence, both singly and doubly charged species are detected as dissociation products. Quite importantly, the observed eliminations of NH(3) or HNCO lead to the formation of new doubly charged species, which turn out to be thermodynamically stable.

On the existence and lifetimes of Cu2+ complexes with water, ammonia, and hydrogen cyanide

High-level ab initio calculations have been carried out to evaluate the lifetimes of complexes formed by the association of Cu2+ to water, ammonia, and hydrogen cyanide. The corresponding binding energies were evaluated at the CCSD(T)6-311+G(3df,2pd) level of theory. The potential-energy curves corresponding to their dissociation into Cu+ + L+ (L=H2O, NH3, and HCN) were obtained at the CCSD(T)6-311+G(3df,2p) level on BHLYP6-311+G(d,p) optimized geometries. Lifetimes were calculated using the exterior complex scaling and the semiclassical WKB methods. Although all the complexes investigated are thermodynamically unstable with respect to their dissociation into Cu+ + L+ in a typical Coulomb explosion, the activation barrier is high enough to accommodate several vibrational resonances, with very large lifetimes. As a matter of fact, if the three complexes are produced in the lowest vibrational levels, they behave as totally bound (with almost infinite lifetime) species.