Catalysis on Photoinduced Electron Transfer

光诱导电子转移的催化

基本信息

批准号：
07454195
负责人：
FUKUZUMI Shunichi
金额：
$ 4.67万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

We have found that Sc^<3+> ion is highly effective for the reduction of benzaldehyde and its derivatives by an NADH analogue at room temperature. The apparent reactivity is shown to be comparable with the enzyme. The catalytic mechanism is discussed based on the comparison of the catalysis of Sc^<3+> on the electron transfer reactions of carbonyl compounds. The hydride transfer reaction from 10-methyl-9,10-dihydroacridine (AcrH_2) to p-benzoquinone (Q) is catalyzed by various metal ions such as Mg^<2+> and rare-earth metal ions in acetonitrile (MeCN). Among triflate salts of metal ions examined, Sc (OTf) _3 was the most effective. The observed second-order rate constant increases with an increase in [Sc^<3+>] at low concentrations, changing to second order dependence at high concentrations. Essentially the same catalytic behavior of Sc^<3+> was observed in the electron transfer reduction of Q by CoTPP (TPP=tetraphenylporphyrin dianion) in MeCN.The second-order dependence of the rate constant with respect to [Sc^<3+>] is ascribed to formation of a 1 : 2 complex between Q^<・-> and Sc^<3+>. The formation of Q^<・->-2Sc^<3+> is confirmed by the ESR spectrum which exhibits the super hyperfine interaction with two equivalent Sc nuclei. Thus, the hydride transfer from AcrH_2 to Q may proceed via Sc^<3+>-catalyzed electron transfer from AcrH_2 to Q.When AcrH_2 is replaced by 1-benzyl-1,4-dihydronicotinamide (BNAH) which is a stronger electron donor than AcrH_2, benzaldehyde and its derivatives are reduced by BNAH efficiently in the presence of Sc^<3+> in MeCN at room temperature to yield the corresponding alcohols. The Sc^<3+> also catalyzes photoinduced electron transfer from the excited state of Ru (bpy) _3^<2+> to benzaldehydes in MeCN.Catalysis of metal ions on various thermal and photoinduced electron transfer reactions has been examined in detail.

我们发现Sc^3+离子在室温下对于NADH类似物还原苯甲醛及其衍生物非常有效，其表观反应活性与酶相当。基于以下讨论了催化机制。 Sc^3+对羰基化合物电子转移反应的催化作用比较10-甲基-9,10-二氢吖啶的氢化物转移反应。 (AcrH_2)在乙腈(MeCN)中被多种金属离子如Mg 2+ 和稀土金属离子催化生成对苯醌(Q)。在所检测的金属离子的三氟甲磺酸盐中，Sc(OTf)_3为。观察到的二阶速率常数在低浓度下随着[Sc^<3+>]的增加而增加，在高浓度下基本上变为二阶依赖性。在 MeCN 中 CoTPP（TPP=四苯基卟啉二价阴离子）对 Q 的电子转移还原中观察到 Sc^<3+> 的相同催化行为。速率常数相对于 [Sc^<3+> 的二阶依赖性]归因于Q^<·->和Sc^<3+>之间形成1:2络合物。Q^<·->-2Sc^<3+>的形成由以下证实。 ESR谱显示出与两个等效Sc核的超精细相互作用。因此，从AcrH_2到Q的氢化物转移可以通过Sc^<3+>-催化从AcrH_2到Q的电子转移进行。当AcrH_2被1-benzyl-取代时。 1,4-二氢烟酰胺(BNAH)是比AcrH_2更强的电子供体，苯甲醛及其衍生物被BNAH还原在室温下，在 MeCN 中存在 Sc^<3+> 的情况下，Sc^<3+> 也能催化光诱导电子从 Ru (bpy)_3^<2+> 的激发态转移到相应的醇。 MeCN 中的苯甲醛。金属离子对各种热和光诱导电子转移反应的催化作用已得到详细研究。