Syntheses,Structures And Luminescent Properties Of Series Of 4d-4f Coordination Complexes

Under hydrothermal methods,eight coordination complexes were synthesized by using the Ln(Ⅲ)ions and 4d10(Ag(Ⅰ)and Cd(Ⅱ))ions as the central metal ions.We choosed the 3,5-pyridinedicarboxylic acid and o-phthalic acid as the main ligands,oxalic acid as assistant ligand.Their structures were studied by Single-crystal X-ray diffraction and the molecular formulars were as follows:(1){PrAg(3,5-PDA)(ox)(H2O)}n(5){DyAg(3,5-PDA)(3,5-HPDA)(ox)0.5(H2O)2}n(2){NdAg(3,5-PDA)(ox)(H2O)}n(6)[Sm2Cd2.5(o-C8H4O4)5(OH(phen)2(H2O)]·H2O(3){HoAg(3,5-PDA)(3,5-HPDA)(ox)0.5(H2O)2}n(7)[Er(2-pzc)2(ox)0.5(H2O)3]·5H2O(4){SmAg(3,5-PDA)(3,5-HPDA)(ox)0.5(H2O)2}n(8)[Ho(bidc)(Hbidc)(H2O)4]·4H2O(1)-(5)are linked to form 2D infinite structure by 3,5-pyridinedicarboxylate and oxalate,which are futher bridged into 3D network structure by oxalate.(6)belongs to the Cd-Sm molecular complex,which is bridged by o-phthalate.(7)and(8)take on binuclear Ln-Ln molecular complexes by using pyrazine-2-carboxylate and benzimidazole-5,6-dicarboxylate as bridging ligands,respectively.Morever,they are joined into 3D hydrogen bonding network by hydrogen bonds.The room temperature IR,UV-Vis-NIR spectra and emission spectra in Vis-and NIR-regions of complexes were determinded and assigned.In the Vis-and NIR-regions,the emission spectra of(1)～(6)present characteristic bands of Ln(Ⅲ)ions,which occur shifting,broad and splitting phenomenon in comparision with theoretical value.In addition to the crystal field,there are interactions between the 4f orbital of Ln(Ⅲ)ions and the 4d orbital of the Ag(I)or Cd(Ⅱ)ions after the formation of 4d-4f complexes,which may make the internal energy levels be adjusted.This phenomenon also exists in the UV-Vis-NIR spectra and they can edvidence each other.Meanwhile the luminescence of eight complexes should be attributted to the sensitization of Ag(Cd)-ligands or ligands.