Sulphur Dioxide Oxidation by Zinc and Zinc Oxide Nitrate/Nitrite Complexes in the Gas Phase: An Interplay between Redox‐Active Ligands and Metal.

Different oxidative pathways of sulphur dioxide promoted by ZnO(NO3)2-, Zn(NO3)2- and Zn(NO2)(NO3)- are revealed by a joint investigation of mass spectrometry and theoretical calculations. The reactions are triggered by the [Zn+2-O-•]+ or by the low-valence Zn+ via oxygen ion transfer or electron transfer to SO2, respectively. The NOx- ligands intervene in the oxidation only when sulphur dioxide is converted to SO3- or SO2-, leading to the formation of zinc sulphate and zinc sulphite coordinated to nitrate or nitrite anions. Kinetic analyses show that the reactions are fast and efficient, and theory discloses the elementary steps, namely oxygen ion transfer, oxygen atom transfer and electron transfer, occurring through similar energy landscapes for the three reactive anions.