Burgert R, Schnöckel H, Grubisic A, Li X, Stokes S T, Bowen K H, Ganteför G F, Kiran B, Jena P
Institute of Inorganic Chemistry, University of Karlsruhe (TH), 76128 Karlsruhe, Germany.
Science. 2008 Jan 25;319(5862):438-42. doi: 10.1126/science.1148643.
The reactivity pattern of small (approximately 10 to 20 atoms) anionic aluminum clusters with oxygen has posed a long-standing puzzle. Those clusters with an odd number of atoms tend to react much more slowly than their even-numbered counterparts. We used Fourier transform ion cyclotron resonance mass spectrometry to show that spin conservation straightforwardly accounts for this trend. The reaction rate of odd-numbered clusters increased appreciably when singlet oxygen was used in place of ground-state (triplet) oxygen. Conversely, monohydride clusters AlnH-, in which addition of the hydrogen atom shifts the spin state by converting formerly open-shell structures to closed-shell ones (and vice versa), exhibited an opposing trend: The odd-n hydride clusters reacted more rapidly with triplet oxygen. These findings are supported by theoretical simulations and highlight the general importance of spin selection rules in mediating cluster reactivity.
小尺寸（约10至20个原子）的阴离子铝簇与氧的反应模式一直是个长期存在的谜题。那些原子数为奇数的簇与原子数为偶数的簇相比，反应往往要慢得多。我们使用傅里叶变换离子回旋共振质谱法表明，自旋守恒直接解释了这一趋势。当使用单线态氧代替基态（三线态）氧时，奇数原子簇的反应速率显著增加。相反，单氢化物簇AlnH-，其中氢原子的添加通过将以前的开壳层结构转变为闭壳层结构（反之亦然）来改变自旋态，呈现出相反的趋势：奇数n的氢化物簇与三线态氧反应更快。这些发现得到了理论模拟的支持，并突出了自旋选择规则在介导簇反应性方面的普遍重要性。
