ESR spectra of superoxide anion-scandium complexes detectable in fluid solution
ESR spectra of superoxide anion-scandium complexes detectable in fluid solution
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DOI：
10.1021/ja981289b
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发表时间：
1999-02-24
影响因子：
15
通讯作者：
Itoh, S
中科院分区：
文献类型：
--
作者：
Fukuzumi, S;Patz, M;Itoh, S
最确定的超氧阴离子O2-的检测，在生命系统中是相当重要的，1是通过ESR光谱进行的，由于氧在含有非质子溶剂的冷冻介质中或在各种固体氧化物表面上在77 k时具有较大的自旋轨道耦合，该光谱给出了一个特征的双线高度各向异性信号。ESR检测o2的缺点是由于溶剂相互作用或轨道简并使轨道角动量猝灭而引起的快速弛豫导致了明显的谱线展宽，这使得在流体溶液中特别是在较高温度下无法进行检测。因此，到目前为止，还没有报道过室温下流体溶液中o2的ESR光谱。我们在此报道，在远高于非质子溶剂熔点的温度下，即使在60℃下，当o2与钪离子形成1:1配合物时，也能成功地获得o2的各向同性ESR谱。钪核引起的超细分裂和富氧17O的超细耦合为溶液中O2—Sc3+络合物的结构提供了有价值的信息。二聚体1-苄基- 1,4 -二氢烟酰胺[(BNA) 2]可以作为独特的双电子给体8，作为电子源光化学还原O2为O2。如方案所示
The most definitive detection of superoxide anion O2-, which is of considerable importance in living systems, 1 has been made by the ESR spectrum which gives a characteristic two-line highly anisotropic signal due to the large spin-orbit coupling of oxygen in frozen media containing aprotic solvents or on various solid oxide surfaces at 77 K. 2-4 However, the disadvantage of the ESR detection of O2-is the significant line broadening resulting from fast relaxation because of the quenching of the orbital angular momentum by fluctuating solvent interactions or orbital degeneracy which has precluded the detection in fluid solution particularly at higher temperatures. 5, 6 Thus, no ESR spectra of O2-have so far been reported in fluid solution at room temperature. 7We report herein that the isotropic ESR spectra of O2-can be obtained successfully in solution at temperatures much higher than the melting point of aprotic solvents even at 60 C when O2-forms a 1: 1 complex with scandium ion. The superhyperfine splitting due to the scandium nucleus and the hyperfine coupling of oxygen enriched in 17O provide valuable information about the structure of the O2--Sc3+ complex in solution. The dimeric 1-benzyl-1, 4-dihydronicotinamide [(BNA) 2], which can act as a unique two-electron donor, 8 is used as an electron source to reduce O2 to O2-photochemically. As shown in Scheme