TY - JOUR AU - Aboshyan-Sorgho, Lilit AU - Nozary, Homayoun AU - Aebischer, Annina AU - Bünzli, Jean-Claude G. AU - Morgantini, Pierre-Yves AU - Kittilstved, Kevin R. AU - Hauser, Andreas AU - Eliseeva, Svetlana V. AU - Petoud, Stéphane AU - Piguet, Claude TI - Optimizing Millisecond Time Scale Near-Infrared Emission in Polynuclear Chrome(III)-Lanthanide(III) Complexes PY - 2012 JF - Journal of the American Chemical Society JA - J. Am. Chem. Soc. SN - 0002-7863 VL - 134 IS - 30 SP - 12675 EP - 12684 L1 - http://pubs.acs.org/doi/pdf/10.1021/ja304009b L2 - http://pubs.acs.org/doi/full/10.1021/ja304009b L3 - http://pubs.acs.org/doi/abs/10.1021/ja304009b L4 - http://www.unige.ch/sciences/chifi/publis/pics/double/ref01306.png M3 - 10.1021/ja304009b UR - http://dx.doi.org/10.1021/ja304009b N2 - 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→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 [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. ID - 1306 ER -