Photosensitized generation of singlet oxygen from ruthenium(II) and osmium(II) bipyridyl complexes
Photosensitized generation of singlet oxygen from ruthenium(II) and osmium(II) bipyridyl complexes
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DOI：
10.1039/b310238f
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发表时间：
2004-01-01
影响因子：
4
通讯作者：
Ershov, AY
中科院分区：
文献类型：
--
作者：
Abdel-Shafi, AA;Worrall, DR;Ershov, AY
报道了一些钌（II）和锇（II）联吡啶配合物在稀乙腈溶液中的光物理性质。的激发态的金属配体电荷转移态（MLCT）的锇配合物的寿命短于钌配合物。发现分子氧猝灭最低激发态金属到配体电荷转移态的速率常数k（q）在（1.1 - 7.7）× 10（9）dm（3）mol（-1）s（-1）范围内。在这些钌和锇络合物的最低激发态的氧猝灭之后，单线态氧产生的效果f（Delta）（T）在0.10 - 0.72的范围内，较低值与具有较低氧化电位的那些化合物相关。激发MLCT状态，k（q），淬灭的速率常数，被发现是一般较高的锇络合物比钌络合物。整体猝灭速率常数，k（q）被发现给被猝灭的激发态的能量的负相关性，也与复合物的氧化电位。然而，当考虑到完全由于能量转移而产生单线态氧的猝灭的贡献k（q）（1）时，其对激发态能量的依赖性更加复杂。由于激发MLCT态的能量耗散而没有能量转移的猝灭速率常数k（q）（3）被发现与络合物的氧化电位有明显的相关性。讨论了影响激发态氧猝灭机制和猝灭后单线态氧生成效率的因素。这些因素包括氧化电位、配合物的最低激发态能量和中心金属的自旋轨道耦合常数。
Photophysical properties for a number ruthenium(II) and osmium(II) bipyridyl complexes are reported in dilute acetonitrile solution. The lifetimes of the excited metal to ligand charge transfer states (MLCT) of the osmium complexes are shorter than for the ruthenium complexes. Rate constants, k(q), for quenching of the lowest excited metal to ligand charge transfer states by molecular oxygen are found to be in the range (1.1 - 7.7) x 10(9) dm(3) mol(-1) s(-1). Efficiencies of singlet oxygen production, f(Delta)(T), following oxygen quenching of the lowest excited states of these ruthenium and osmium complexes are in the range of 0.10 - 0.72, lower values being associated with those compounds having lower oxidation potentials. The rate constants for quenching of the excited MLCT states, k(q), are found to be generally higher for osmium complexes than for ruthenium complexes. Overall quenching rate constants, k(q) were found to give an inverse correlation with the energy of the excited state being quenched, and also to correlate with the oxidation potentials of the complexes. However, when the contribution of quenching due exclusively to energy transfer to produce singlet oxygen, k(q)(1), is considered, its dependence on the energy of the excited states is more complex. Rate constants for quenching due to energy dissipation of the excited MLCT states without energy transfer, k(q)(3), were found to show a clear correlation with the oxidation potential of the complexes. Factors affecting both the mechanism of oxygen quenching of the excited states and the efficiency of singlet oxygen generation following this quenching are discussed. These factors include the oxidation potential, the energy of the lowest excited state of the complexes and spin - orbit coupling constant of the central metal.