A Novel Three-Dimensional Network Containing Pr(III) Ions and Tartrate: Synthesis, Spectroscopic, Thermal, Ab Initio X-ray Powder Structure Analyses, and Photoluminescence Properties

Abstract

A new praseodymium tartrate [Pr(C4H4O6)(C4H5O6)(H2O)] has been synthesized under hydrothermal conditions and investigated by UV−Vis, FTIR, X-ray powder diffraction, thermal and photoluminescence analyses. The compound crystallizes in the orthorhombic system with a = 21.973(4), b = 7.587(1), c = 5.958(1) Å, space group P212121, and Z = 4. The crystal structure has been solved from laboratory X-ray powder diffraction data using a direct space global optimization technique and refined by the Rietveld method. The Pr atoms in the complex have 9-fold coordination with respect to the oxygens, with the metal center in a distorted monocapped square antiprism coordination. The molecular structure of the complex reveals 22-membered (Pr4C10O8) nanosized rectangular motifs assembled into helical chains, which are further linked via carboxylate groups of the tartrate ligands forming a novel three-dimensional polymeric framework. A X-ray powder pattern of the anhydrous praseodymium tartrate obtained by heating the title compound at 230 °C revealed a monoclinic unit cell with a = 10.964(3), b = 11.612(2), c = 10.456(4) Å, β = 108.96(2)°. The luminescence spectra of the hydrated Pr complex exhibit a signal at 645 nm due to a 3P0 → 3F2 transition.