Effect of Proton Substitution by Alkali Ions on the Fluorescence Emission of Rhodamine B Cations in the Gas Phase

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• 作者：Jean-Fran莽ois Greisch ; Michael E. Harding ; Wim Klopper ; Manfred M. Kappes ; Detlef Schooss
• 刊名：Journal of Physical Chemistry A
• 出版年：2014
• 出版时间：May 29, 2014
• 年：2014
• 卷：118
• 期：21
• 页码：3787-3794
• 全文大小：350K
• 年卷期：v.118,no.21(May 29, 2014)
• ISSN：1520-5215

文摘

The photophysics of chromophores is strongly influenced by their environment. Solvation, charge state, and adduct formation significantly affect ground and excited state energetics and dynamics. The present study reports on fluorescence emission of rhodamine B cations (RhBH⁺) and derivatives in the gas phase. Substitution of the acidic proton of RhBH⁺ by alkali metal cations, M⁺, ranging from lithium to cesium leads to significant and systematic blue shifts of the emission. The gas-phase structures and singlet transition energies of RhBH⁺ and RhBM⁺, M = Li, Na, K, Rb, and Cs, were investigated using Hartree鈥揊ock theory, density functional methods, second-order M酶ller鈥揚lesset perturbation theory, and the second-order approximate coupled-cluster model CC2. Comparison of experimental and theoretical results highlights the need for improved quantum chemical methods, while the hypsochromic shift observed upon substitution appears best explained by the Stark effect due to the inhomogeneous electric field generated by the alkali ions.