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).

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

“…Another factor contributing to the enhanced quantum yields might be the effective energy transfer of the secondary ligand to the triplet state of the primary ligand due to overlap of the singlet and triplet levels of the bidentate nitrogen ligand and primary ligand. Moreover, the observed quantum yields and lifetime values, especially those for 3 and 4, were found to be promising when compared with those reported recently for a terbium 5-(thiophen-3-yl)-isophthalate complex (Φ = 7.46 % and τ = 213.9 µs in aqueous solution), [22] a terbium-thiophenyl-derivatized nitrobenzoate complexes (Φ = 4.7-9.8 % and τ = 208-725 µs in methanol solution) [21] and a terbium complex of thiophene carboxylic acid (τ = 230 µs in solid state).…”

“…On the other hand, longer lifetime values were observed for complexes 3 and 4 due to the absence of nonradiative decay pathways. The observed quantum yields and lifetime values, especially those for 4, are promising when compared with the recently reported 5-(thiophen-3-yl)isophthalate-terbium complex (Φ = 7.46 % and τ = 213.9 µs in aqueous solution), [22] terbium-thiophenyl-derivatized nitrobenzoate complexes (Φ = 4.7-9.8 % and τ = 208-725 µs in methanol solution) [21] and the terbium complex of thiophenecarboxylic acid (τ = 230 µs in solid state).…”

“…[21,22] A preliminary study by Malta and coworkers [23] demonstrated that thiopheneacetic acid (HTPAC) can be used as a potential sensitizer for lanthanide emissions. However, to the best of our knowledge, systematic investigations of the luminescent properties of terbium thiopheneacetate complexes in the presence of bidentate nitrogen donors and the structural characterization of such complexes by single-crystal X-ray diffraction have not been reported previously.…”

Lanthanide‐Based Coordination Polymers Assembled by a Flexible Multidentate Linker: Design, Structure, Photophysical Properties, and Dynamic Solid‐State Behavior

“…[8] Recently, several lanthanide coordination polymers with interesting photophysical properties, a few of which couple luminescence and porosity, have been reported. [9][10][11][12][13][14][15][16] However, lanthanide systems remain far less studied than frameworks based on d-block transition-metal elements [17][18][19][20] because the typically unspecific coordination properties of the lanthanide ions render the design of lanthanide-based coordination frameworks with specific properties very challenging. By contrast, the coordination flexibility of lanthanide ions can lead to unusual structural topologies and new framework families.…”

Structure Variation and Luminescence Properties of Lanthanide Complexes Incorporating a Naphthalene‐Derived Chromophore Featuring Salicylamide Pendant Arms

“…[5][6][7][8][9][10][11][12] Most of the described materials are based on transition metal ions and have multidimensional structures with geometrically simple repeating units from the templating effect of the transition metal ions, which generally show low coordination numbers. Only a few examples of coordination polymers that incorporate lanthanide ions are known, [13][14][15][16][17][18][19][20] along with some examples of high-nuclearity lanthanide clusters. [21][22][23][24] However, these large ions achieve high and variable coordination numbers with irregular geometries, leading to potentially highly luminescent coordination polymers with more complicated features.…”