Synthetic, structural, and luminescence study of uranyl coordination polymers containing chelating terpyridine and trispyridyltriazine ligands

Abstract

Seven uranyl coordination polymers [(UO₂)(BrC₈H₃O₄)(C₁₅H₁₁N₃)] (1), [(UO₂)(ClC₈H₃O₄)(C₁₅H₁₁N₃)] (2), [(UO₂)(BrC₈H₃O₄)(C₁₈H₁₂N₆)]·H₂O (3), [(UO₂)(ClC₈H₃O₄)(C₁₈H₁₂N₆)]·2H₂O (4), [(UO₂)(C₈H₃IO₄)(C₁₈H₁₂N₆)]·2C₃H₇O (5), [(UO₂)(C₉H₆O₄)(C₁₈H₁₂N₆)]·H₂O (6), and [(UO₂)(C₆H₂O₄S)(C₁₈H₁₂N₆)]·2H₂O (7) containing N-donor ligands 2,2′:6′,2′′-terpyridine (TPY) and 2,4,6-tripyridyl s-triazine (TPTZ); and O-donor linkers thiophene 2,5-dicarboxylic acid (TDC) and X-1,4-benzene dicarboxylic acid (X-BDC, where X = Me, Cl, Br, I) were synthesized and characterized using single crystal X-ray diffraction (SC-XRD), powder X-ray diffraction (PXRD), and fluorescence spectroscopy. Each compound crystallizes as binuclear pseudo dimers containing a UO₂²⁺ pentagonal bipyramidal primary building unit. Fluorescence spectra of 1–4, and 6–7 show characteristic UO₂²⁺ emission whereas 5 is non-emissive. Red shifts within the emission of 1–4 are noted as a function of N-donor ligands TPY and TPTZ whereas emission shifts are not observed in TPTZ bearing compounds (3, 4, 6, 7) containing different O-donor linkers. Luminescent lifetimes of 1–7 were obtained and fitted with either bi-exponential or tri-exponential components.