Comparison of ruthenium(II) and cyclometalated iridium(III) azacrown ether phenanthroline hybrids for the detection of metal cations by electrochemiluminescence.
Comparison of ruthenium(II) and cyclometalated iridium(III) azacrown ether phenanthroline hybrids for the detection of metal cations by electrochemiluminescence.
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DOI：
10.1039/c000449a
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发表时间：
2010-05
影响因子：
4
通讯作者：
Hengwei Lin;M. Cinar;M. Schmittel
中科院分区：
文献类型：
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作者：
Hengwei Lin;M. Cinar;M. Schmittel
两个氮杂冠醚附加铱（III）配合物，1和3，被描述为金属阳离子的氧化还原电化学发光（ECL）与三正丙胺作为共反应物在乙腈中操作的探针。配合物1和3分别对Ba（2+）和Ag（+）表现出显著的电化学发光敏感性，发光强度增强了9倍，λmax（em）发生了前所未有的红移。相比之下，结构类似的氮杂冠醚附加的钌（II）络合物2和4在添加相同的金属离子时仅显示出不显著的ECL变化并且没有波长偏移。理解这种差异的关键是理解负责金属吸收的氮杂冠醚菲咯啉配体代表铱（III）络合物中的LUMO，但却是钌类似物的HOMO的一部分。因此，氧化还原ECL过程的电子转移平衡导致无金属的受激钌体系2* 和4* 的优先形成。相比之下，铱络合物1和3在发射状态下保持与金属离子配位，因为氧化涉及铱苯基喹啉部分，其不参与阳离子结合。
Two azacrown ether appended iridium(III) complexes, 1 and 3, are described as probes for metal cations operating on oxidative-reduction electrochemiluminescence (ECL) with tri-n-propylamine as coreactant in acetonitrile. Complexes 1 and 3 exhibit a notable ECL sensing for Ba(2+) and Ag(+), respectively, through a 9-fold emission intensity enhancement and an unprecedented λmax(em) red shift. In contrast, the structurally analogous azacrown ether appended ruthenium(II) complexes 2 and 4 only display insignificant ECL changes and no wavelength shift upon addition of the same metal ions. The key to understand this disparity is to appreciate that the azacrown ether phenanthroline ligand, responsible for metal uptake, represents the LUMO in iridium(III) complexes but is part of the HOMO for the ruthenium analogs. As a consequence, the electron transfer equilibria of the oxidative-reduction ECL process lead to a preferential formation of the metal free, excited ruthenium systems 2* and 4*. In contrast, the iridium complexes 1 and 3 remain coordinated to metal ions in the emitting state, as the oxidation involves the iridium phenylquinoline part, which is not invoked in cation binding.