Self-assembly of 1D coordination polymers of two rare-earth complexes with carboxylate linkages: Synthesis, crystal structure and DFT studies

Two new lanthanide carboxylato complexes [Ln(3,5-DNBA)3(H2O)2]n, (Ln = LaIII in 1 and GdIII in 2, DNBA = dinitrobenzoic acid) have been synthesized hydrothermally and characterized structurally by single crystal X-ray analysis. Alternate (μ-η1:η1)4 and (μ-η1:η1)2 type bridging modes by carboxylate ligands provide eightfold coordination around the Ln center in both complexes, which result in two different Ln⋯⋯Ln distances, with polymeric chains propagating along the [1 0 0] direction. Intermolecular O–H⋯⋯O hydrogen bonds and π–π stacking interactions form R22(20), R44(40) rings, thus generating three-dimensional supramolecular frameworks in 1 and 2. Density functional theory (DFT) calculations were carried out using the hybrid exchange–correlation functional, PBE. The HOMO–LUMO energy gap of 2.63 eV in 1 is found to be greater than that of 1.86 eV in 2.

Graphical abstractTwo new lanthanide carboxylato complexes [Ln(3,5-DNBA)3(H2O)2]n, (Ln = LaIII in 1 and GdIII in 2, DNBA = dinitrobenzoic acid) have been synthesized hydrothermally and characterized structurally by single crystal X-ray analysis. A 1D polymeric chain is accomplished by alternate (μ-η1:η1)4 and (μ-η1:η1)2 type bridging modes from carboxylate ligands, providing an eightfold coordination around the Ln center in both complexes, with different Ln⋯⋯Ln distances. Geometry-optimized, spin-unrestricted, density functional theory (DFT) calculations have been performed to calculate the electronic structures.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Isostructural 1D polymers of rare-earth complexes with carboxylate linkages. ► (μ-η1:η1)4/(μ-η1:η1)2 modes provide eightfold Ln centers with different distances. ► A 3D supramolecular network consisting of R22(20), R44(40) ring motifs. ► Electronic properties calculated by the DFT method.