This work reports two lanthanide clusters, Ln4(RPO3)2(RPO3H)(tBuCO2)7(tBuCO2H)3(H2O)3 (Ln = Eu, Tb; RPO3H2 denotes (9-methyl-9H-fluoren-9-yl)phosphonic acid). A comprehensive series of characterizations was performed for the Eu4 and Tb4 clusters, including X-ray crystallography, X-ray scintillation, and photoluminescence spectroscopy, to elucidate their structural features and physicochemical properties. Notably, these clusters exhibit exceptional X-ray scintillation performance, attributed to the characteristic luminescence of Ln3+ ions. This finding paves the way for the development of novel scintillator materials and enriches the family of lanthanide-bearing clusters with X-ray scintillating properties. Furthermore, photoluminescence modulation was achieved for the chemically mixed Eu/Tb analogues, c-EuxTb4-x (x = 2.67, 2, 1.33), and physically mixed Eu4/Tb4 materials, p-yEu4:zTb4 (y:z = 2:1, 1:1, 1:2), with varying the excitation wavelength. Notably, near-white-light emission is realized for p-Eu4:2Tb4 upon excitation at 365 nm. Collectively, these tetranuclear lanthanide phosphonates exhibit excitation-wavelength and Eu3+:Tb3+ ratio dependent luminescence, indicating their potential as color-tunable luminescent materials and white-light-emitters.
Zhou et al. (Tue,) studied this question.