Lanthanide coordination polymers based on designed bifunctional 2-(2,2′:6′,2″-terpyridin-4′-yl)benzenesulfonate ligand: syntheses, structural diversity and highly tunable emission

Abstract

Seven novel lanthanide coordination polymers, [Eu(STP)(glu)] n (1), [Ln4(STP)2(glu)5] n ·4nH2O [Ln = Er (2), Yb (3)], [Ln(STP)(1,3-bdc)] n ·0.5nH2O [Ln = Tb (4), Yb (5)], and [Ln(STP)(1,2-bdc)] n [Ln = Eu (6), Tb (7)] [NaSTP = sodium 2-(2,2′:6′,2″-terpyridin-4′-yl)benzenesulfonate, H2glu = glutaric acid, H2(1,3-bdc) = benzene-1,3-dicarboxylic acid, H2(1,2-bdc) = benzene-1,2-dicarboxylic acid], have been prepared under hydrothermal conditions and characterized by elemental analysis, IR and single-crystal X-ray diffraction. Compound (1) possesses a 2D layered structure based on 1D chains with STP− and glu2− anions acting as bridges. Compounds (2) and (3) are isomorphous and show a rare 3D tcj/hc net with a tetranuclear Ln3+ unit regarded as a seven-connected node and a glu2− anion serving as a three-connected node. Compounds (4) and (5) are isomorphous and exhibit six-connected pcu nets by denoting binuclear units to six-connected nodes. Compounds (6) and (7) display 3D 3,5T1 nets with (1,2-bdc)2− anions and dimetallic units serving as three- and five-connected nodes, respectively. The Eu compounds (1) and (6) demonstrate typically red emission, while the Tb compounds (4) and (7) exhibit characteristic green emission. The emission spectra of heteronuclear compounds [Eu x Tb1−x (STP)(1,2-bdc)] n (0 ≤ x ≤ 1) as efficient luminescent tags were investigated. The intermetallic energy transfer of Tb to Eu was also evaluated.