Triplet Excited State Distortions in a Pyrazolate Bridged Platinum Dimer Measured by X-ray Transient Absorption Spectroscopy

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• 作者：Jenny V. Lockard ; Aaron A. Rachford ; Grigory Smolentsev ; Andrew B. Stickrath ; Xianghuai Wang ; Xiaoyi Zhang ; Klaus Atenkoffer ; Guy Jennings ; Alexander Soldatov ; Arnold L. Rheingold ; Felix N. Castellano
• 刊名：Journal of Physical Chemistry A
• 出版年：2010
• 出版时间：December 9, 2010
• 年：2010
• 卷：114
• 期：48
• 页码：12780-12787
• 全文大小：267K
• 年卷期：v.114,no.48(December 9, 2010)
• ISSN：1520-5215

文摘

The excited-state structure of a dinuclear platinum(II) complex with tert-butyl substituted pyrazolate bridging units, [Pt(ppy)(μ-^tBu₂pz)]₂ (ppy = 2-phenylpyridine; ^tBu₂pz = 3,5-di-tert-butylpyrazolate) is studied by X-ray transient absorption (XTA) spectroscopy to reveal the transient electronic and nuclear geometry. DFT calculations predict that the lowest energy triplet excited state, assigned to a metal−metal-to-ligand charge transfer (MMLCT) transition, has a contraction in the Pt−Pt distance. The Pt−Pt bond length and other structural parameters extracted from fitting the experimental XTA difference spectra from full multiple scattering (FMS) and multidimensional interpolation calculations indicates a metal−metal distance decrease by approximately 0.2 Å in the triplet excited state. The advantages and challenges of this approach in resolving dynamic transient structures of nonbonding or weak-bonding dinuclear metal complexes in solution are discussed.