Bond Shortening (1.4 脜) in the Singlet and Triplet Excited States of [Ir2(dimen)4]2+ in Solution Determined by Time-Resolved X-ray Scattering

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• 作者：Kristoffer Haldrup ; Tobias Harlang ; Morten Christensen ; Asmus Dohn ; Tim Brandt van Driel ; Kasper Skov Kj忙r ; Niels Harrit ; Johan Vibenholt ; Laurent Guerin ; Michael Wulff ; Martin Meedom Nielsen
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：October 3, 2011
• 年：2011
• 卷：50
• 期：19
• 页码：9329-9336
• 全文大小：945K
• 年卷期：v.50,no.19(October 3, 2011)
• ISSN：1520-510X

文摘

Ground- and excited-state structures of the bimetallic, ligand-bridged compound Ir₂(dimen)₄²⁺ 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) 脜 and a triplet excited-state lifetime of 410(70) ns. A model incorporating the presence of two ground-state structures differing in Ir鈥揑r separation is demonstrated to fit the obtained data very well, in agreement with previous spectroscopic investigations. Two ground-state isomers with Ir鈥揑r separations of 3.60(9) and 4.3(1) 脜 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)₄²⁺.