X-ray Scintillating Lanthanide-Based Coordination Polymers

Reported are the syntheses and characterization of 25 lanthanide-containing coordination polymers exhibiting four structure types: type I′: [Ln(TFTP)1.5(bpy)] (Ln = La3+–Nd3+), type I: [Ln(TFTP)1.5(bpy)(H2O)] (Ln = Sm3+–Lu3+), type II′: [Pr(TFTP)1.5(phen)], and type II: [Ln(TFTP)1.5(phen)(H2O)] (Ln = Nd3+–Yb3+, excluding Pm). These compounds feature lanthanide metal cations bound to tetrafluoroterephthalate linkers (TFTP) and either, 2,2′-bipyridine (bpy) or 1,10-phenanthroline (phen) capping ligands. Initial calculations using crystallographic data revealed large void spaces, ranging from 86 Å3 in type I to 333 Å3 in type II. Yet, adsorption isotherm data indicate very little gas uptake of both materials with a BET surface area of 9 m2/g for I-Tb (8) and 19 m2/g for II-Tb (20). X-ray irradiation of I-Eu (6), II-Eu (18), I-Tb (8), and II-Tb (20) produced visible red and green emission, respectively. Radioluminescence studies of both type I and II with Sm3+, Eu3+, and Tb3+ metal centers indicate that both structure types featuring Tb3+ are brighter than those with Eu3+ or Sm3+. Notably, structure type I with Tb3+ is the brightest scintillator with a relative luminosity of 1.7× that of bismuth germanate (BGO).