Isophthalato-Based 2D Coordination Polymers of Eu(III), Gd(III), and Tb(III): Enhancement of the Terbium-Centered Luminescence through Thiophene Derivatization

Abstract

We present here the first examples of lanthanide ion complexes with only isophthalic acid or thiophenylisophthalic acid ligands. The complexes of isophthalic acid with Eu(3+) (1) and Tb(3+) (2) and the moderately soluble complexes of 5-thiophen-3-ylisophthalate with Eu(3+) (3), Gd(3+) (4), and Tb(3+) (5) were isolated as single crystals through gel crystallization. X-ray diffraction studies confirm the cross-linking structure of these complexes, which, in case of the thiophenyl derivatives, results in low solubility in common solvents. The two-dimensional isophthalato complex of Eu(3+) (1) crystallizes in the C2/c space group, with a = 22.154(4), b = 12.649(3), and c = 15.921(3) A, beta = 112.34(3) degrees, and V = 4126.7(14) A(3), while the one-dimensional Tb(3+) complex of the same ligand, 2, crystallizes in the space group P2(1)/c with a = 11.921(2), b = 10.838(2), and c = 17.499(4) A, beta = 92.44(3) degrees, and V = 2258.9(8) A(3). The thiophenylisophthalato complexes of Eu(3+) (3) and Gd(3+) (4) are two-dimensional and crystallize in the P2/n space group with parameters for 3 of a = 14.139(3), b = 10.684(2), and c = 15.138(3) A, beta = 102.51(3) degrees, and V = 2232.3(8) A(3) and parameters for 4 of a = 14.1195(13), b = 10.6594(10), and c = 15.1149(14) A, beta = 102.529(2) degrees, and V = 2220.7(4) A(3), while the Tb(3+) complex, 5, also two-dimensional, crystallizes in the P space group with a = 11.051(2), b = 14.528(3), and c = 15.041(3) A, alpha = 77.63(3), beta = 87.86(3), and gamma = 83.51(3) degrees, and V = 2343.48 A(3). All complexes of Eu(3+) and Tb(3+) luminesce in aqueous solution, and the luminescence lifetimes and quantum yields are 123.8 +/- 7.4, 0.14% (1), 475.1 +/- 14.5, 3.58% (3), 129.3 +/- 3.5, 0.19% (4), and 213.9 +/- 2.2 micros, 7.46% (5).