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

Martin Kristoffer Haldrup, Tobias Harlang, Morten Christensen, Asmus Ougaard Dohn, Tim Brandt van Driel, Kasper Skov Kjær, Niels Harrit, Johan Vibenholt, Laurent Guerin, Michael Wulff, Martin Meedom Nielsen

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    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) 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)42+.
    Original languageEnglish
    JournalInorganic Chemistry
    Volume50
    Issue number19
    Pages (from-to)9329-9336
    ISSN0020-1669
    DOIs
    Publication statusPublished - 2011

    Keywords

    • Materials characterisation and modelling

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