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