Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
J Phys Chem A. 2011 Sep 22;115(37):10245-50. doi: 10.1021/jp203990w. Epub 2011 Aug 25.
Lanthanum oxide cluster anions are prepared by laser ablation and reacted with n-C(4)H(10) in a fast flow reactor. A time-of-flight mass spectrometer is used to detect the cluster distribution before and after the reactions. (La(2)O(3))(m=1-3)OH(-) and La(3)O(7)H(-) are observed as products, which suggests the occurrence of hydrogen atom abstraction reactions: (La(2)O(3))(m=1-3)O(-) + n-C(4)H(10) → (La(2)O(3))(m=1-3)OH(-) + C(4)H(9) and La(3)O(7)(-) + n-C(4)H(10) → La(3)O(7)H(-) + C(4)H(9). Density functional theory (DFT) calculations are performed to study the structures and bonding properties of La(2)O(4)(-), La(3)O(7)(-), and La(4)O(7)(-) clusters. The calculated results show that each of La(2)O(4)(-) and La(4)O(7)(-) contains one oxygen-centered radical (O(-•)) which is responsible for the high reactivity toward n-C(4)H(10). La(3)O(7)(-) contains one oxygen-centered radical (O(-•)) and one superoxide unit (O(2)(-•)), and the O(-•) is responsible for its high reactivity toward n-C(4)H(10). The O(-•) and O(2)(-•) can be considered to be generated by the adsorption of an O(2) molecule onto the singlet La(3)O(5)(-) with electron transfer from a terminally bonded oxygen ion (O(2-)) to the O(2). This may help us understand the mechanism of the formation of O(-•) and O(2)(-•) radicals in lanthanum oxide systems. The reaction mechanisms of La(2)O(4)(-) + n-C(4)H(10) and La(3)O(7)(-) + n-C(4)H(10) are also studied by the DFT calculations, and the calculated results are in good agreement with the experimental observations.
氧化镧团簇阴离子通过激光烧蚀制备，并在快速流动反应器中与正辛烷反应。使用飞行时间质谱仪检测反应前后的团簇分布。观察到(La₂O₃)ₘ=1-3)OH⁻和 La₃O₇H⁻作为产物，这表明发生了氢原子抽取反应：(La₂O₃)ₘ=1-3)O⁻+n-C₄H₁₀→(La₂O₃)ₘ=1-3)OH⁻+C₄H₉和 La₃O₇⁻+n-C₄H₁₀→La₃O₇H⁻+C₄H₉。通过密度泛函理论(DFT)计算研究了 La₂O₄⁻、La₃O₇⁻和 La₄O₇⁻团簇的结构和键合性质。计算结果表明，每个 La₂O₄⁻和 La₄O₇⁻都含有一个氧中心自由基(O⁻•)，这是其对正辛烷具有高反应性的原因。La₃O₇⁻含有一个氧中心自由基(O⁻•)和一个超氧自由基单元(O₂⁻•)，O⁻•负责其对正辛烷的高反应性。O⁻•和 O₂⁻•可以被认为是通过 O₂分子吸附到单重态 La₃O₅⁻上，并通过电子从末端键合的氧离子(O₂⁻)转移到 O₂而产生的。这有助于我们理解氧化镧体系中 O⁻•和 O₂⁻•自由基形成的机制。还通过 DFT 计算研究了 La₂O₄⁻+n-C₄H₁₀和 La₃O₇⁻+n-C₄H₁₀的反应机制，计算结果与实验观察结果吻合良好。
