Optimizing Millisecond Time Scale Near-Infrared Emission in Polynuclear Chrome(III)鈥揕anthanide(III) Complexes

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• 作者：Lilit Aboshyan-Sorgho ; Homayoun Nozary ; Annina Aebischer ; Jean-Claude G. B眉nzli ; Pierre-Yves Morgantini ; Kevin R. Kittilstved ; Andreas Hauser ; Svetlana V. Eliseeva ; St茅phane Petoud ; Claude Piguet
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：August 1, 2012
• 年：2012
• 卷：134
• 期：30
• 页码：12675-12684
• 全文大小：568K
• 年卷期：v.134,no.30(August 1, 2012)
• ISSN：1520-5126

文摘

This work illustrates a simple approach for optimizing long-lived near-infrared lanthanide-centered luminescence using trivalent chromium chromophores as sensitizers. Reactions of the segmental ligand L2 with stoichiometric amounts of M(CF₃SO₃)₂ (M = Cr, Zn) and Ln(CF₃SO₃)₃ (Ln = Nd, Er, Yb) under aerobic conditions quantitatively yield the D₃-symmetrical trinuclear [MLnM(L2)₃](CF₃SO₃)_n complexes (M = Zn, n = 7; M = Cr, n = 9), in which the central lanthanide activator is sandwiched between the two transition metal cations. Visible or NIR irradiation of the peripheral Cr(III) chromophores in [CrLnCr(L2)₃]⁹⁺ induces rate-limiting intramolecular intermetallic Cr鈫扡n energy transfer processes (Ln = Nd, Er, Yb), which eventually produces lanthanide-centered near-infrared (NIR) or IR emission with apparent lifetimes within the millisecond range. As compared to the parent dinuclear complexes [CrLn(L1)₃]⁶⁺, the connection of a second strong-field [CrN₆] sensitizer in [CrLnCr(L2)₃]⁹⁺ significantly enhances the emission intensity without perturbing the kinetic regime. This work opens novel exciting photophysical perspectives via the buildup of non-negligible population densities for the long-lived doubly excited state [Cr*LnCr*(L2)₃]⁹⁺ under reasonable pumping powers.