Remote site photosubstitution in metalloporphyrin-rhenium tricarbonylbipyridine assemblies: photo-reactions of molecules with very short lived excited states
Remote site photosubstitution in metalloporphyrin-rhenium tricarbonylbipyridine assemblies: photo-reactions of molecules with very short lived excited states
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DOI：
10.1039/b806267f
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发表时间：
2008-01-01
影响因子：
4
通讯作者：
Perutz, Robin N.
中科院分区：
文献类型：
--
作者：
Gabrielsson, Anders;Smith, John R. Lindsay;Perutz, Robin N.
报道了一系列金属卟啉（和相应的游离碱卟啉）的合成，它们通过一个苯基的4-位上的酰胺键被联吡啶基团单内消旋取代：[Re（CO）（3）（Pic）Bpy-MTPP][OTf]，其中M = Mg，Zn，Pd或2 H，Pic = 3-甲基吡啶，Bpy = 2，2 '-联吡啶，TPP =四苯基卟啉。的光化学反应的组件与牺牲的电子给体三乙胺已通过红外光谱法进行了研究，并进行了比较的行为的类型Bpy-MTPP没有ESTA。选择性的长波长照射的金属卟啉单位在过量的甲基吡啶的存在下，导致还原在cubibipyridine中心。在不存在3-甲基吡啶的情况下，后者不被还原，而是被添加的卤化物或被THF溶剂取代。机理分析突出了一方面锌和镁螯合物与另一方面钯卟啉之间的差异。游离碱组装体[Re（CO）（3）（Pic）Bpy-H2 TPP][OTf]是不反应的。锌和镁卟啉组装体在经历来自三乙胺的光诱导内球电子转移以形成组装体的电荷移位激发态之前最初配位Et 3 N。相比之下，钯基二分体通过基于卟啉的激发态的外层还原淬灭反应。取代产物被假定为通过涉及电子转移链的机制形成。
The synthesis is reported of a series of metalloporphyrins (and the corresponding free-base porphyrin), mono-meso-substituted with a bipyridyl group via an amide link at the 4-position of one phenyl group: [Re(CO)(3)(Pic) Bpy-MTPP][OTf], whereM= Mg, Zn, Pd or 2H, Pic = 3-picoline, Bpy = 2,2'-bipyridine, TPP = tetraphenylporphyrin. The photochemical reactions of the assemblies with the sacrificial electron donor triethylamine have been investigated by IR spectroscopy and compared to the behaviour of analogues of the type Bpy-MTPP without rhenium. Selective long-wavelength irradiation of the metalloporphyrin unit in the presence of excess picoline leads to reduction at the rhenium bipyridine centre. In the absence of 3-picoline, the latter is not reduced, but substituted by added halide or by the THF solvent. Mechanistic analysis highlights the differences between the zinc and magnesium chelate on the one hand and the palladium porphyrin on the other. The free-base assembly, [Re(CO)(3)(Pic) Bpy-H2TPP][OTf] is unreactive. The zinc and magnesium porphyrin assemblies initially coordinate Et3N before undergoing photo-induced inner-sphere electron transfer from the triethylamine to form a charge-shifted excited state of the assembly. In contrast, the palladium-based dyad reacts via outer-sphere reductive quenching of a porphyrin-based excited state. The substitution products are postulated to form by a mechanism involving an electron-transfer chain.