Self-Assembly of a Two-Dimensional Coordination Polymer Based on Silver and Lanthanide Tetrakis-Acylpyrazolonates: An Efficient New Strategy for Suppressing Ligand-to-Metal Charge Transfer Quenching of Europium Luminescence.

A new strategy for the easy polymerization of anionic [Ln(Q)] (HQ-4-(cyclohexanecarbonyl)-5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one) into two-dimensional layers of [AgLn(Q)] (Ln = Sm, Eu, Gd, Tb and Dy) is proposed by binding the single molecular anions [Ln(Q)] to silver cations through the coordination of the pyridinic nitrogen atoms of the pyrazolonate rings. The luminescent properties of [AgLn(Q)] have been studied in detail, and it was shown that the previously described low photoluminescence quantum yield (PLQY) of [Eu(Q)] is due to Ligand-To-Metal Charge Transfer (LMCT) quenching, which is effectively suppressed in the heterometallic [AgEu(Q)] polymer. Sensibilization coefficients for HO[Eu(Q)], [AgEu(Q)], and HO[Sm(Q)] complexes (n ≈ 1) were estimated via theoretical analysis (also by using Judd-Ofelt theory for Sm) and PLQY measurements.