Synthesis, Crystal Structures, And Photoluminescent Properties Of Several Rare Earth Carboxylate Complexes

On account of their diversiform structures and excellent chemical andspectroscopic properties, luminescent rare earth complexes have considerable importantapplications in a wide range of optical applications, including optical communications,multicolor displays, and organic light-emitting diodes (OLEDs). In particular,luminescent Tb3+and Eu3+complexes have recently attracted more attention owing totheir potential applications in biomedical analyses and cell and tissue imaging. In thispaper, para-substituted benzoic acid derivatives and2-aryl propionic acid derivatives ofnon-steroidal anti-inflammatory drugs were introduced as ligands, fourteen rare earthcomplexes have been synthesized. The crystal structures, thermal stability, andphotoluminescent properties have been systemically studied.Firstly,4-fluorobenzoic acid and4-nitrobenzoic acid were employed as ligands,four europium and terbium complexes,{[Ln(FBA)3(H2O)4] H2O}n[Ln=Eu (1), Tb (2)]and {[Ln2(NBA)6(H2O)4] H2O}n[Ln=Eu (1), Tb (2)], have been synthesized. Andthree single crystals were obtained by a hydrothermal method. The structures of themwere established by X-ray crystallography, which reveales that {[Ln(FBA)3(H2O)4] H2O}n[Ln=Eu (1), Tb (2)] are isostructural and crystallized into one infinite1Dchains by bidentate bridging carboxyl groups. Each Tb3+or Eu3+center is located in thecenter of distorted square antiprism formed by the eight coordinated oxygen atoms.There are four coordinated and one free H2O molecules around each Tb3+or Eu3+center.{[Ln2(NBA)6(H2O)4] H2O}n[Ln=Eu (1), Tb (2)] also crystallized into one infinite1Dchains by (μ:η1-η1)1(μ:η1-η2)2and (μ:η1-η1)2bridging modes. Each Tb3+or Eu3+centeris located in the center of distorted three capped tritriangular prism formed by the ninecoordinated oxygen atoms. The thermal stability and photoluminescent properties of thefour complexes were investigated by the thermogravimetric analyses (TGA) and thesolid state fluorescence spectrum, which illustrated that4-fluorobenzoic acid is suitablefor the sensitization of Eu3+and Tb3+emission. And the corresponding complexes haveexcellent thermal stability. They could be considered as potential emitting materials forthe fabrication of OLEDs.Secondly,2-aryl propionic acid derivatives of non-steroidal anti-inflammatorydrugs carprofen, naproxen and flurbiprofen were introduced as ligands, ten homonu- clear and heteronuclear rare earth complexes have been synthesized. The crystalstructure of [Eu2(CPF)6(DMF)2] is established by X-ray crystallography, which revealesthat the molecule consists of a homodinuclear form. Each Eu3+center is eightcoordinated. The coordination polyhedron around the central Eu3+can be described as adistorted trigonal dodecahedron or square antiprism. The bridging binding modes thatcontain two bidentate and two tridentate bridges can be termed as (μ: η1-η1)2(μ: η2-η1)2.The photoluminescent properties of the ten complexes were investigated by the solidstate fluorescence spectrum, which illustrated that flurbiprofen is more suitable thancarprofen and naproxen for the sensitization of Eu3+and Tb3+emission. Furthermore,we described energy transfer from Tb3+to Eu3+in Eu/Tb heteronuclear NPF and FPFsystem, and the energy transfer efficiency are80%and96%respectively.