Ground state structures of Fe(2)O(4-6)(+) clusters probed by reactions with N(2)

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 113; no. 18; p. 5302
• Main Authors: Xue, Wei, Yin, Shi, Ding, Xun-Lei, He, Sheng-Gui, Ge, Mao-Fa
• Format: Journal Article
• Language: English
• Published: United States 07.05.2009
• Subjects: Ferric Compounds - chemistry; Mass Spectrometry; Molecular Probes - chemistry; Nitrogen - chemistry; Quantum Theory; Sensitivity and Specificity; Thermodynamics
• ISSN: 1520-5215; 1520-5215
• DOI: 10.1021/jp810426s

Reactions of small cationic iron oxide clusters (Fe(2)O(4-6)(+)) with N(2) are investigated by experiments and first principle calculations. The cationic iron oxide clusters are generated by reaction of laser ablated iron plasma with O(2) in a supersonic expansion, and are reacted with N(2) in a fast flow reactor at near room temperature conditions. Cluster cations are detected by a time-of-flight mass spectrometer. The substitution reaction Fe(2)O(n)(+) + N(2) --> Fe(2)O(n-2)N(2)(+) + O(2) is observed for n = 5 but not for n = 4 and 6. Density functional theory calculations predict that the low-lying energy structures of Fe(2)O(4-6)(+) are with side-on (eta(1)-O(2)) or end-on (eta(2)-O(2)) bonded molecular oxygen unit(s). The calculations further predict that the substitution of eta(1)-O(2) and eta(2)-O(2) in Fe(2)O(4,6)(+) clusters by N(2) is exothermic and subject to negative and positive overall reaction barriers, respectively, at room temperature. We thus propose that the ground state structures of Fe(2)O(4)(+) and Fe(2)O(6)(+) contain eta(2)-O(2). In contrast, both the experiment and theory favor a eta(1)-O(2) in the ground state structure of Fe(2)O(5)(+).