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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，在室温下，Sc~(2+)~(3+)对NADH类似物还原苯甲醛及其衍生物是非常有效的。表观反应活性与该酶相当。通过比较Sc~(2+)、Lt；~(3+)、Gt~(3+)对羰基化合物电子转移反应的催化作用，探讨了其催化机理。10-甲基-9，10-二氢吖啶(AcrH_2)向对苯二酚(Q)的氢化转移反应是在多种金属离子的催化下进行的。在所考察的金属离子的三氟盐中，Sc(OTf)3的效果最好。观察到的二级速率常数在低浓度时随[Sc^&lt；3+&gt；]的增加而增大，在高浓度时转变为二级依赖关系。CoTPP(TPP=四苯基卟啉二阴离子)在MeCN.中催化Q的电子转移还原反应中，Sc^&lt；3+和Gt；的催化行为基本相同.速率常数对[Sc^&lt；3+&gt；]的二级依赖性归因于Q^&lt；·-&gt；与Sc^&lt；3+&gt；之间形成1：2的络合物.ESR谱证实了Q^&lt；·-&gt；-2Sc^&lt；3+&gt；的形成，它与两个等价的Sc核发生超精细相互作用。当AcrH_2被比AcrH_2更强的电子供体1-苄基-1，4-二氢烟酰胺(BNAH)取代时，苯甲醛及其衍生物在Sc^&lt；3+&gt；的存在下，在室温下可被BNAH有效地还原生成相应的醇。此外，Sc~(2+)还能催化Ru(Bpy)_3~(2+)激发态向苯甲醛的光致电子转移。