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