Synthesis, Crystal Structure, and Photoluminescence of Homodinuclear Lanthanide 4-(Dibenzylamino)benzoate Complexes

Abstract

Three new binuclear lanthanide complexes of general formula [Ln 2 (L) 6 (H 2 O) 4 ] (Ln = Tb (1), Eu (2), and Gd (3)) supported by the novel aromatic carboxylate ligand 4-(dibenzylamino)benzoic acid (HL) have been synthesized. Complexes 1 and 2 were structurally characterized by single-crystal X-ray diffraction. Both 1 and 2 crystallize in the triclinic space group P 1 , and their molecular structures consist of homodinuclear species that are bridged by two oxygen atoms from two carboxylate ligands via different coordination modes. The discrete bridged dimer of 1 is centrosymmetric and features 8-coordinate terbium atoms, each of which adopts a distorted square-antiprismatic geometry. Both coordination spheres comprise two η 2 -chelating benzoates, two μ-η 1 :η 1 -carboxylate interactions from the bridging benzoates, and two water molecules. By contrast, in complex 2, the Eu 3þ ion coordination environment is best described as a distorted tricapped-trigonal prism, each europium ion being coordinated to three η 2 -chelating benzoate ligands and two water molecules. One of the η 2 -carboxylate ligands is involved in a further interaction with an adjacent metal, thus rendering the overall binding mode bridging tridentate, μ-η 2 :η 1 . Scrutiny of the packing diagrams for 1 and 2 revealed the existence of a one-dimensional molecular array that is held together by intermolecular hydrogen-bonding interactions. The Tb 3þ complex 1 exhibits high green luminescence efficiency in the solid state with a quantum yield of 82%. On the other hand, poor luminescence efficiency has been noted for the Eu 3þ -4-(dibenzylamino)benzoate complex.

Crystal structure of triaqua(2,2'-bipyridyl)(2,3-naphthalenedicarboxylato) nickel(II), Ni(H2O)3(C10H8N2)(C12H6O4)

“…The design of suitable organic ligands favoring structurespecific self-assembly is one of the keys for the construction of discrete coordination architectures. In fact, besides coordination bonding, some weak intra-or intermolecular intermolecular interactions, such as hydrogen bonding [5,6], p···p stacking [7,8] and C-H···p [9,10] interactions also affect the final structures of the complexes, and they may further link discrete subunits or lowdimensional entities into higher-dimensional supramolecular frameworks [5][6][7][8][9][10].…”

Synthesis, crystal structure and photophysical properties of lanthanide coordination polymers of 4-[4-(9H-carbazol-9-yl)butoxy]benzoate: the effect of bidentate nitrogen donors on luminescence

“…3 It was also demonstrated that replacement of the hydrogens of the NH 2 moiety of p-aminobenzoic acid by benzyl groups had a significant influence on the distribution of π-electron density within the ligand system and resulted in the development of a novel solid state photosensitizer for Tb 3+ with an overall quantum yield of 82%. 4 Subsequent investigations from our group also revealed that the presence of electron-releasing or electron-withdrawing groups on position 3 of the 4-benzyloxy benzoic acid ligand has a profound effect on the π-electron density of the ligands and consequently on the photosensitization of the Ln 3+ ions. Specifically, the presence of a methoxy substituent in this position results in a significant improvement in the photoluminescence efficiency of the Tb 3+ -3-methoxy-4-benzyloxy benzoate complex in comparison with that of the 4-benzyloxy benzoate complex (10-33%).…”

Preparation, Crystal structure and Luminescence Properties of Lanthanide Complexes with 2,4,6-tri(pyridin-2-yl)-1,3,5-triazine and Organic Carboxylic Acid

“…Among the five emission bands, the electric dipole transition 5 D0→ 7 F2 around 616 nm is the strongest. In addition, the ratio of electric dipole transition and magnetic dipole transition ( 5 D0→ 7 F1) of Complexes 1 and 2 are 3.31 and 4.28, respectively, which indicates that the coordination environment of Eu 3+ complexes are not center symmetric [50][51][52][53][54]. The luminescence intensities of electric dipole transition of Complexes 1 and 2 are 0.74 × 10 5 and 1.4 × 10 5 , respectively.…”