2-Thiopheneacetato-Based One-Dimensional Coordination Polymer of Tb3+: Enhancement of Terbium-Centered Luminescence in the Presence of Bidentate Nitrogen Donor Ligands

Four new lanthanide(III) complexes of 2-thiopheneacetic acid (HTPAC), [Tb(TPAC)(3)center dot H2O](n) (1), [Gd(TPAC)(3)center dot H2O](n) (2), [Tb(TPAC)(3)(phen)](2) (3) and [Tb(TPAC)(3)(bath)](2) (4) (phen = 1,10-phenanthroline; bath = bathophenanthroline) have been synthesized and characterized by various spectroscopic techniques. The X-ray structure of 1 reveals that each Tb3+ ion is connected to two neighboring ions by six thiopheneacetic acid ligands via the carboxylate groups to form an infinite one-dimensional polymer. The unit cell contains only one independent crystallographic site for the Tb ions. The carboxylate groups of the six molecules of the thiopheneacetate ligands are coordinated in both bidentate bridging and tridentate chelate-bridging modes. Each Tb3+ ion is coordinated by nine oxygen atoms in an overall distorted tricapped trigonal-prismatic geometry. Eight of the oxygen atoms are furnished by the carboxylate moieties, and the remaining oxygen atom is provided by the water molecule. The photophysical properties of these complexes in the solid state at room temperature have been investigated. The quantum yields of 3 (4.43 +/- 0.44 %) and 4 (9.06 +/- 0.90 %) were found to be significantly enhanced by the presence of the bidentate nitrogen donor ligands in comparison with that of 1 (0.07 +/- 0.01 %) due to effective energy transfer from the secondary ligands. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)