The present work describes a complementary experimental and theoretical investigation of the spectroscopic properties of the four isostructural 3D Ln-MOFs (wherein PDC = pyrazole-3,5-dicarboxylate, [La2(PDC)3(H2O)4]·2H2O (1), [(La0.9Eu0.1)2(PDC)3(H2O)4]·2H2O (2), [(La0.9Tb0.1)2(PDC)3(H2O)4]·2H2O (3) and [(La0.9Eu0.5Tb0.5)2(PDC)3(H2O)4]·2H2O (4)). The experimental data and theoretical calculations show that the singular photophysical properties presented by these Ln-MOFs are induced by strong interaction between the Ln(3+) ions.
New thiophene-dipicolinato-based compounds, K 2 nTdpa (n = 1, 2), were isolated. Their anions are sensitizers of lanthanide ion (Ln III ) luminescence and singlet oxygen generation ( 1 O 2 ). Emission in the visible and near-infrared regions was observed for the Ln III complexes with efficiencies (ϕ Ln ) ϕ Eu = 33% and ϕ Yb = 0.31% for 1Tdpa 2− and ϕ Yb = 0.07% for 2Tdpa 2− . The latter does not sensitize Eu III emission. Fluorescence imaging of HeLa live cells incubated with K 3 [Eu(1Tdpa) 3 ] indicates that the complex permeates the cell membrane and localizes in the mitochondria. All complexes generate 1 O 2 in solution with efficiencies (ϕ O 1 2 ) as high as 13 and 23% for the Gd III complexes of 1Tdpa 2− and 2Tdpa 2− , respectively. [Ln(nTdpa) 3 ] 3− (n = 1, 2) are phototoxic to HeLa cells when irradiated with UV light with IC 50 values as low as 4.2 μM for [Gd(2Tdpa) 3 ] 3− and 91.8 μM for [Eu(1Tdpa) 3 ] 3− . Flow cytometric analyses indicate both apoptotic and necrotic cell death pathways.
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