Centre for Molecular Movies, Technical University of Denmark, Risø National Laboratory, Materials Department, Roskilde, Denmark.
Inorg Chem. 2011 Oct 3;50(19):9329-36. doi: 10.1021/ic2006875. Epub 2011 Aug 8.
Ground- and excited-state structures of the bimetallic, ligand-bridged compound Ir2(dimen)4(2+) are investigated in acetonitrile by means of time-resolved X-ray scattering. Following excitation by 2 ps laser pulses at 390 nm, analysis of difference scattering patterns obtained at eight different time delays from 250 ps to 300 ns yields a triplet excited-state distance between the two Ir atoms of 2.90(2) Å and a triplet excited-state lifetime of 410(70) ns. A model incorporating the presence of two ground-state structures differing in Ir–Ir separation is demonstrated to fit the obtained data very well, in agreement with previous spectroscopic investigations. Two ground-state isomers with Ir–Ir separations of 3.60(9) and 4.3(1) Å are found to contribute equally to the difference scattering signal at short time delays. Further studies demonstrate the feasibility of increasing the effective time resolution from the 100 ps probe width down to the 10 ps regime by positioning the laser pump pulse at selected points in the X-ray probe pulse. This approach is used to investigate the structures of both the singlet and the triplet excited states of Ir2(dimen)4(2+).
采用时间分辨 X 射线散射方法，在乙腈中研究了桥联配体的双金属配合物 Ir2(dimen)4(2+)的基态和激发态结构。在 390nm 处用 2ps 激光脉冲激发后，在 250ps 至 300ns 的 8 个不同时间延迟处获得的差分散射图谱的分析，得出两个 Ir 原子之间的三重态激发态距离为 2.90(2)Å，三重态激发态寿命为 410(70)ns。证明了一个包含两种基态结构的模型，这两种基态结构在 Ir–Ir 分离方面存在差异，非常符合之前的光谱研究。发现两种基态异构体的 Ir–Ir 分离分别为 3.60(9)和 4.3(1)Å，在短时间延迟时对差分散射信号的贡献相等。进一步的研究表明，通过将激光泵浦脉冲定位在 X 射线探针脉冲的选定点，可以将有效时间分辨率从 100ps 探测脉冲宽度提高到 10ps 范围，从而提高有效时间分辨率。该方法用于研究 Ir2(dimen)4(2+)的单重态和三重态激发态的结构。
