Ground State Structures of Fe2O4−6 + Clusters Probed by Reactions with N2

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 113; no. 18; pp. 5302 - 5309
• Main Authors: Xue, Wei, Yin, Shi, Ding, Xun-Lei, He, Sheng-Gui, Ge, Mao-Fa
• Format: Journal Article
• Language: English
• Published: American Chemical Society 07.05.2009
• Subjects: A: Kinetics, Spectroscopy
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp810426s

Reactions of small cationic iron oxide clusters (Fe2O4−6 +) with N2 are investigated by experiments and first principle calculations. The cationic iron oxide clusters are generated by reaction of laser ablated iron plasma with O2 in a supersonic expansion, and are reacted with N2 in a fast flow reactor at near room temperature conditions. Cluster cations are detected by a time-of-flight mass spectrometer. The substitution reaction Fe2O n + + N2 → Fe2O n-2N2 + + O2 is observed for n = 5 but not for n = 4 and 6. Density functional theory calculations predict that the low-lying energy structures of Fe2O4−6 + are with side-on (η1-O2) or end-on (η2-O2) bonded molecular oxygen unit(s). The calculations further predict that the substitution of η1-O2 and η2-O2 in Fe2O4,6 + clusters by N2 is exothermic and subject to negative and positive overall reaction barriers, respectively, at room temperature. We thus propose that the ground state structures of Fe2O4 + and Fe2O6 + contain η2-O2. In contrast, both the experiment and theory favor a η1-O2 in the ground state structure of Fe2O5 +.