Syntheses,Structure And Luminescent Properties Of Series Of Ln-ag Coordination Polymers

Eight Ln-Ag coordination polymers were synthesized by the hydrothermal method.The crystal structure of the polymers were determined by X-single crystal diffraction and the molecular formulas are listed as following:（1）{PrAg（PDA）₂（H₂O）₃·2H₂O}_n（5）{TbAg（PDA）₂（H₂O）₃·3H₂O}_n（2）{NdAg（PDA）₂（H₂O）₃·2H₂O}_n（6）{DyAg（PDA）₂（H₂O）₃·3H₂O}_n（3）{Sm Ag（PDA）₂（H₂O）₃·3H₂O}_n（7）{EuAg（PDA）₂（H₂O）₃·H₂O}_n（4）{GdAg（PDA）₂（H₂O）₃·3H₂O}_n（8）{ErAg（PDA）₂（H₂O）₃·H₂O}_nIn the eight coordination polymers use the pyridine-2,6-dicarboxylate is the main ligand,and Ln（III）and Ag（I）are the central metal ions.Polymers（1）and（2）possess the 2D layer structure,and polymers（3）-（8）present the 1D chains,which are further linked into 2D hydrogen bondoxy network by O-H…O hydrogen bonds.At room remperature,the IR and UV-Vis-NIR absorption spectra,excitation and emission spectra in the visible and near-infrared regions of the eigth polymers were measured and analyzed.Except the coordination polymer（4）,the other coordination polymers exhibit characteristic emission bands of corresponding Ln（III）ions,which should be attributed to sensitization from the Ag-ligands moiety.In the influence of crystal field and the 4d orbitals from the Ag（I）ion,the 4f orbitals of Ln（III）are adjusted and part of the energy levels present obvious shift.These are shown in the NIR emission spectra,i.e,the emission bands present shift relate to the theoretoal emissions of Ln（III）ions.In addition,part of the absorption bands of Ln（III）ions also present shift on the UV-Vis-NIR spectra,and the two spectra can evidence each other.