Thermochemical properties of the ammonia-water ionized dimer probed by ion-molecule reactions. - Archive ouverte HAL Access content directly
Journal Articles Journal of Physical Chemistry A Year : 2005

Thermochemical properties of the ammonia-water ionized dimer probed by ion-molecule reactions.

(1) , (1)
1

Abstract

The thermochemical properties of some small clusters such as the (H2O)2*+ dimer have already been investigated by both experimental and theoretical methods. The recent method to selectively prepare the ammonia-water ionized dimer [NH3, H2O]*+ (and not its proton transfer isomer [NH4+, OH*]) allowed us to study its chemical reactivity. This study focuses on the charge and proton transfer pathways: Ion-molecule reactions in the cell of an FT-ICR mass spectrometer were carried out with a range of organic compounds. Examination of the reactivity of the [NH3, H2O]*+ ionized dimer versus ionization energy and proton affinity of the neutral reagents shows a threshold in the reactivity in both instances. This leads to a bracketing of thermochemical properties related to the dimer. From these experiments and in agreement with ab initio calculations, the adiabatic recombination energy of the [NH3, H2O]*+ dimer was evaluated at -9.38 +/- 0.04 eV. The proton affinity bracketing required the reevaluation of two reference gas-phase basicity values. The results, in good agreement with the calculation, lead to an evaluation of the proton affinity of the [NH2*, H2O] dimer at 204.4 +/- 0.9 kcal mol(-1). These two experimental values are respectively related to the ionization energy of NH3*+ and to the proton affinity of NH2* by the difference in single water molecule solvation energies of ionized ammonia, of neutral ammonia, and of the NH2* radical.

Dates and versions

hal-00916201 , version 1 (11-12-2013)

Identifiers

Cite

Safwat A. Azeim, Guillaume van Der Rest. Thermochemical properties of the ammonia-water ionized dimer probed by ion-molecule reactions.. Journal of Physical Chemistry A, 2005, 109 (11), pp.2505-2513. ⟨10.1021/jp045425c⟩. ⟨hal-00916201⟩
37 View
0 Download

Altmetric

Share

Gmail Facebook Twitter LinkedIn More