The thermal gas-phase reaction of [NOH]+ with nitric oxide (NO) has been studied using FT-ICR mass spectrometry complemented by high level quantum chemical calculations. Among different competitive paths that may be envisioned, using D- and 15N labelling in the reagent species has allowed to unequivocally observe an exclusive electron transfer (ET) reactivity. This outcome is well accounted by the energy profile for the envisioned plausible pathways calculated at UCCSD(T)/aug-ccpVTZ//UB3LYP/def2-TZVP level of theory. The seemingly barrierless ET process (as predicted by classical Marcus theory) is exoergonic by 20.8 kcal/mol. The two reaction partners may alternatively yield an adduct, where a large extent of charge transfer has taken place. This [HNO⋅⋅⋅NO]+ adduct may proceed by undergoing transfer of hydrogen, entailing largely hydride character. However, in agreement with a calculated barrier of ca. 12 kcal/mol, no experimental evidence is obtained for the occurrence of this alternative route.
Prevailing charge transfer in the reaction of protonated and neutral nitric oxide: A theoretical and experimental study / Usharani, D.; Crestoni, M. E.; Fornarini, S.. - In: INTERNATIONAL JOURNAL OF MASS SPECTROMETRY. - ISSN 1387-3806. - 471:(2022), p. 116724. [10.1016/j.ijms.2021.116724]