Optimizing millisecond time scale near-infrared emission in polynuclear chrome(III)-lanthanide(III) complexes |
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Authors: | Aboshyan-Sorgho Lilit Nozary Homayoun Aebischer Annina Bünzli Jean-Claude G Morgantini Pierre-Yves Kittilstved Kevin R Hauser Andreas Eliseeva Svetlana V Petoud Stéphane Piguet Claude |
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Institution: | Department of Inorganic, Analytical and Applied Chemistry, University of Geneva, Geneva, Switzerland. |
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Abstract: | 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(CF(3)SO(3))(2) (M = Cr, Zn) and Ln(CF(3)SO(3))(3) (Ln = Nd, Er, Yb) under aerobic conditions quantitatively yield the D(3)-symmetrical trinuclear MLnM(L2)(3)](CF(3)SO(3))(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→Ln 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 CrN(6)] 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. |
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