Complete Photochromic Structural Change of Ruthenium(II)-Diimine Complexes Based on the Control of the Excited States by Metallation
Complete Photochromic Structural Change of Ruthenium(II)-Diimine Complexes Based on the Control of the Excited States by Metallation
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基于金属化控制激发态的钌(II)-二亚胺配合物的完全光致变色结构变化
DOI：
10.1002/chem.201300437
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
and T. Kojima
中科院分区：
文献类型：
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作者：
T. Sawaki;T. Ishizuka;M. Kawano;Y. Shiota;K. Yoshizawa;and T. Kojima
研究了新合成的配合物[RuII（TPA）（tpphz）]2+（1; TPA=三（2-吡啶甲基）胺，tpphz=四吡啶并[3，2-a：2 '，3'-c：3 ''，2 ''-h：2 '，3'-j]吩嗪）及其衍生物的热反应和光化学反应。加热络合物1（封闭形式）及其衍生物在MeCN中的溶液，导致TPA配体的一个吡啶甲基部分部分解离，并且在Ru II中心上产生的空位被来自溶剂的MeCN分子占据，以定量产率分别得到解离的络合物[Ru II（η3-TPA）（tpphz）（MeCN）]2+（1′，开放形式）及其衍生物。在动力学分析的基础上研究了热分解反应，表明反应通过七配位过渡态进行。虽然MLCT吸收带的光照射诱导了后向反应，但络合物1 ′的光反应在络合物1和1 ′之间达到光稳定状态，因此络合物1从络合物1 ′的回收率为67%。当配合物1在tpphz配体的空位上质子化后，配合物1 +H+从配合物1 ′+H+中光诱导回收的效率提高到83%。相比之下，双核μ-tpphz配合物2和3，其包含RuII（TPA）（tpphz）单元和在tpphz配体的另一配位边缘上的RuII（bpy）2或PdIICl 2部分，表现出从其开放形式到其封闭形式的100%光转化（2′→ 2和3 ′→3）。这些结果是过渡金属络合物的完全光致变色结构变化的第一个例子，如其开放和封闭形式之间的完全相互转化所代表的。通过进行光学和电化学测量的审查，使我们能够提出一个合理的解释，即金属配位在tpphz配体的空位上如何提高从开放形式到封闭形式的光转换效率。必须通过金属配位使闭合形式的三重金属-配体电荷转移激发态（3 MLCT *）的能级相对于三重金属中心激发态（3 MC *）的能级降低。这种能级操纵阻碍了从3 MLCT * 态到3 MC * 态的跃迁，从而阻止了TPA配体的部分光解。
The thermal and photochemical reactions of a newly synthesized complex, [RuII(TPA)(tpphz)]2+(1; TPA=tris(2‐pyridylmethyl)amine, tpphz=tetrapyrido[3,2‐a:2′,3′‐c:3′′,2′′‐h: 2′′′,3′′′‐j]phenazine), and its derivatives have been investigated. Heating a solution of complex1(closed form) and its derivatives in MeCN caused the partial dissociation of one pyridylmethyl moiety of the TPA ligand and the resulting vacant site on the RuIIcenter was occupied by a molecule of MeCN from the solvent to give a dissociated complex, [RuII(η3‐TPA)(tpphz)(MeCN)]2+(1′, open form), and its derivatives, respectively, in quantitative yields. The thermal dissociation reactions were investigated on the basis of kinetics analysis, which indicated that the reactions proceeded through a seven‐coordinate transition state. Although the backwards reaction was induced by photoirradiation of the MLCT absorption bands, the photoreaction of complex1′reached a photostationary state between complexes1and1′and, hence, the recovery of complex1from complex1′was 67 %. Upon protonation of complex1at the vacant site of the tpphz ligand, the efficiency of the photoinduced recovery of complex1+H+from complex1′+H+improved to 83 %. In contrast, dinuclear μ‐tpphz complexes2and3, which contained the RuII(TPA)(tpphz) unit and either a RuII(bpy)2or PdIICl2moiety on the other coordination edge of the tpphz ligand, exhibited 100 % photoconversion from their open forms into their closed forms (2′→2and3′→3). These results are the first examples of the complete photochromic structural change of a transition‐metal complex, as represented by complete interconversion between its open and closed forms. Scrutinization by performing optical and electrochemical measurements allowed us to propose a rationale for how metal coordination at the vacant site of the tpphz ligand improves the efficiency of photoconversion from the open form into the closed form. It is essential to lower the energy level of the triplet metal‐to‐ligand charge‐transfer excited state (3MLCT*) of the closed form relative to that of the triplet metal‐centered excited state (3MC*) by metal coordination. This energy‐level manipulation hinders the transition from the3MLCT* state into the3MC* state in the closed form to block the partial photodissociation of the TPA ligand.