A series of isostructural lanthanide complexes [Ln(MPQ) 3 ] (Ln = Nd, Gd, Er, Yb, Lu) using a monoanionic tridentate methylpyridyl-substituted 8-hydroxyquinoline ligand (MPHQ = 2-(5-methylpyridin-2-yl)-8-hydroxyquinoline) have been prepared and characterized using elemental analysis (CHN), single-crystal X-ray diffraction (XRD), and 1 H NMR spectroscopy. This ligand forms homoleptic charge-neutral lanthanide complexes with three coordinated ligands arranged in an "up−up−down" fashion around the metal center. The photophysical properties of the Nd, Er, and Yb complexes were investigated using absorption and emission spectroscopy, with the latter species displaying efficient sensitization in the Near Infra-Red (NIR) region and a photoluminescence quantum yield (PLQY) as high as 1.0% in CH 2 Cl 2 solution. The intersystem crossing and energy-transfer processes involved in the antenna effect were further investigated using transient absorption techniques, which revealed essentially quantitative sensitization efficiencies for the NIR-emitting cations.

A visible light absorbing [RuII(tpy)2]2+-type chromophore appended with a dipicolinic acid LnIII chelator has been prepared and complexed with several differing lanthanide cations to form the corresponding heterobimetallic d-f assemblies....

A series of lanthanide-based coordination polymers {[Yb1-xErx(4,4'-bpdo)3(H2O)2](CF3SO3)3}∞ were synthesised by solvent diffusion techniques, where 4,4'-bpdo = 4,4'-bipyridine-N,N'-dioxide, and using differing mole fractions of Yb(iii) and Er(iii) which were systematically varied (x = 0, 0.05, 0.20, 0.50 and 1). All of the materials obtained were characterised using elemental analyses, single-crystal X-ray diffraction (SXRD) and solid-state photoluminescence studies. Structurally, the coordination polymers crystallise as an isomorphous series of infinite 2D sheets, which contain two inner sphere water molecules, and are isostructural with a previously characterised homometallic Yb(iii) compound. In addition to the normal Near Infra-Red (NIR) luminescence, these compounds also demonstrate upconversion emission upon 980 nm excitation. Upconversion luminescence measurements reveal visible emission in the red, green, and blue regions corresponding to the (2)H11/2→(4)I15/2, (4)F9/2→(4)I15/2 and (2)H9/2→(4)I15/2 transitions of the Er(iii) cation upon two and three-photon excitation. We also observed weak emission from the Er(iii) cation in the UV region for the first time in a Ln-MOF based material.

Enhanced near-infrared (NIR) luminescence from two structurally related heterobinuclear NaIYbIII eight-cooridnate and heterobinuclear YbIIINaI eight-coordinate (CN = 8) complexes is reported and compared to a nine-coordinate (CN = 9) homoleptic complex. For the heteroleptic complex, [Yb­(MPQ2)­(acac)], the YbIII cation is coordinated to two tridentate 2-(5-methylpyridin-2-yl)-8-quinolinate (MPQ) anions, with a bidentate acetylacetonate (acac) anion completing the coordination sphere. Instead, the heterobinuclear [NaYb­(MPQ)4] complex comprises a total of four anionic MPQ ligands, two of which exhibit κ3-coordination to the YbIII cation. The remaining two MPQ anions are unidentate toward the lanthanide and form μ2-bridges via the deprotonated quinolinate oxygens to a bound NaI cation which is also coordinated to the remaining nitrogen donor atoms. The structural properties of these complexes were evaluated by single-crystal X-ray diffraction (SXRD), continuous shape measure (CShM) analysis, and 1H NMR spectroscopy using a diamagnetic LuIII analogue. The corresponding photophysical properties were examined in CH2Cl2 solution by using absorption and emission spectroscopy. For both the complexes, characteristic YbIII emission is observed at ca. 980 nm, with recorded photoluminescence quantum yields (Φobs) and NIR luminescence lifetimes (τobs) of 2.0% and 14.0 μs vs 1.5% and 11.6 μs for the [NaYb­(MPQ)4] and [Yb­(MPQ)2(acac)] complexes, respectively. Interestingly, the eight-coordinate YbIII complexes both have higher photoluminescence quantum yields when compared to the homoleptic [Yb­(MPQ)3] complex, which has a reported quantum yield of 1.0% and a NIR lifetime determined herein of 13.3 μs under identical conditions. These results have been rationalized by considering the overall efficiency of the ligand-centered sensitization process (ηsens = Φisc × Φeet), together with subsequent radiative (k r) and nonradiative (k nr) deactivation of the YbIII cation. Moreover, the efficiency of the intersystem crossing (Φisc) and electronic energy transfer (Φeet) processes involved in the antennae effect have been quantified for the new complexes using a combination of nanosecond and femtosecond transient absorption techniques and have been compared to our previous results using [Ln­(MPQ)3] complexes with Ln = Yb and Lu.