Tetrametallic Terbium/Europium Fluorenylphosphonate With Excellent X‐Ray Scintillating and Photo‐Induced Luminescence

ABSTRACT This work reports two lanthanide clusters, [Ln 4 (RPO 3 ) 2 (RPO 3 H)( t BuCO 2 ) 7 ( t BuCO 2 H) 3 (H 2 O) 3 ] (Ln = Eu, Tb; RPO 3 H 2 denotes (9‐methyl‐9H‐fluoren‐9‐yl)phosphonic acid). A comprehensive series of characterizations was performed for the Eu 4 and Tb 4 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 Ln 3+ 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‐ Eu x Tb 4‐x (x = 2.67, 2, 1.33), and physically mixed Eu 4 / Tb 4 materials, p‐y Eu 4 :z Tb 4 (y:z = 2:1, 1:1, 1:2), with varying the excitation wavelength. Notably, near‐white‐light emission is realized for p‐ Eu 4 :2 Tb 4 upon excitation at 365 nm. Collectively, these tetranuclear lanthanide phosphonates exhibit excitation‐wavelength and Eu 3+ :Tb 3+ ratio dependent luminescence, indicating their potential as color‐tunable luminescent materials and white‐light‐emitters.