Site-selective Eu( iii ) spectroscopy of highly efficient luminescent mixed-metal Pb( ii )/Eu( iii ) coordination polymers

Novel mixed-metal coordination polymers (CPs) based on Pb 1−x Eu x –BDC ( x = 0.05, 0.10, 0.25, 0.50 and BDC = 1,4-benzenedicarboxylic acid) are reported. The materials display different coordination structures as the Pb : Eu metal ratio is modified. Whereas for x < 0.25 the Eu 3+ ions essentially replace the Pb 2+ ones in the [Pb(BDC) n ] structure, for x > 0.25 the samples are isotypical with [Eu 2 (BDC) 3 (H 2 O) 4 ], as shown by powder (including Rietveld analysis) and single-crystal X-ray diffraction. The unique Pb 0.75 Eu 0.25 –BDC compound displays a mixture of both crystalline phases with the highest emission quantum yield value reported for luminescent CPs based on Pb( ii ), 69 ± 7%. Site-selective excitation using a common Xe lamp permits the detailed study of the two Eu 3+ local sites, illustrating how powerful the Eu 3+ luminescence is as a local probe spectroscopic tool.