Abdel-Shafi Ayman A, Bourdelande Jose L, Ali Sameh S
Department of Chemistry, Faculty of Science, Ain Shams University, 11566, Abbassia, Cairo, Egypt.
Dalton Trans. 2007 Jun 28(24):2510-6. doi: 10.1039/b705524b. Epub 2007 May 23.
Photophysical properties in dilute acetonitrile solution are reported for a number of iridium(III) and rhenium(I) complexes. The nature of the lowest excited state of the complexes under investigation is either metal-to-ligand charge transfer ((3)MLCT) or a ligand centred ((3)LC) state. Rate constants, k(q), for quenching of the lowest excited states by molecular oxygen are in the range 1.5 x 10(8) to 1.4 x 10(10) M(-1) s(-1). Efficiency of singlet oxygen production, f(Delta)(T), following oxygen quenching of the lowest excited states of these complexes, are in the range of 0.27-1.00. The rate constants and the efficiency of singlet oxygen formation are quantitatively reproduced by a model that assumes the competition between a non-charge transfer (nCT) and a CT deactivation channel. The balance between CT and nCT deactivation channels, which is described by the relative contribution p(CT) of CT induced deactivation, is discussed. The kinetic model is found to be successfully applied in the case of quenching of the excited triplet states of coordination compounds by oxygen in acetonitrile, as was proposed for the quenching of pi-pi* triplet states by oxygen.
报道了多种铱（III）和铼（I）配合物在稀乙腈溶液中的光物理性质。所研究配合物的最低激发态性质为金属到配体的电荷转移（(3)MLCT）或配体中心（(3)LC）态。通过分子氧猝灭最低激发态的速率常数k(q)在1.5×10(8)至1.4×10(10) M(-1) s(-1)范围内。这些配合物最低激发态经氧猝灭后单线态氧产生效率f(Delta)(T)在0.27 - 1.00范围内。速率常数和单线态氧形成效率通过一个假设非电荷转移（nCT）和电荷转移（CT）失活通道之间竞争的模型进行定量再现。讨论了由CT诱导失活的相对贡献p(CT)所描述的CT和nCT失活通道之间的平衡。如针对氧猝灭π-π*三重态所提出的那样，发现该动力学模型成功应用于乙腈中氧猝灭配位化合物激发三重态的情况。
