Syntheses,Structure And Photophysical Properties Of Series Of Ln(?) Coordination Polymers

In this article,nine coordination polymers were designed and synthesized via hydrothermal methods-Their crystal structures were determined by X-ray diffraction and formulas were lised as following:(1){[Sm2(2,6-pydc)(ox)2·(H2O)4]·3H2O}n(2){[Eu2(2,6-pydc)(ox)2(H2O)4]·3H2O}n(3){[Gd2(2,6-pydc)(ox)2·(H2O)4]·3H2O}n(4){[TRb2(2,6-pydc)(ox)2·(H20)4]·3H2O}n(5){Py2(2,6-pydc)(ox)2·(H2O)4]·3H2O}n(6){[Ho2(2,6-pydc)(ox)2'(H20)4]3H20}n(7){[Er2(2,6-pydc)(ox)2-(H2O)4]·3H2O}n(8){[Nd(C4H6O4)0.5(ox)0.5(OH)]·H2O}n(9){[PrZn0.5(2,3-pydc)(C4H6O4)(H2O)2]·3H2O}nPolymers(1)-(7)are isomorphous,all crystals are in the triclinic system,with space group P-1.In the crystals,there exist two inequivalent Ln(III)ions and these Ln(III)ions are connected into an infinite 3D network structure by pyridine-2,6-dicarboxylates and oxalates.At the same time,there are O-H…O hydrogen bonds in them.Polymer(8)is bridged into 3D network through flexible oxalate and fumaric acid.Polymer(9)is Pr-Zn heterometallic coordination polymer,when is connected into the 3D structure with pyridine-2,3-dicarboxylates as bridging ligands while the succinates are used as an auxiliary ligand.The IR spectra,UV-Vis-NIR absorption spectra,UV-Vis and NIR fluorescence spectra are determined and assigned for the nine coordination polymers,and the luminescent properties of the polymers were studied in emphasis.Except the polymers(3)and(8),the other polymers exhibit characteristic emission bands of corresponding Ln(III)ions,which should be attributed to sensitization of the ligands or Zn-ligand section.In addition,the NIR emission bands of some polymers persent shift in comparison with the corresponding theoretical emission bands of Ln(III)ions.This may be due to that under the influence of the crystal field the internal energy levels may be adjusted,i.e.,part of energy levels of Ln(III)ions present shift and split,which could be supported in their UV-Vis-NIR specrtra and NIR emission specrtra.Shift and broadness of emission bands are very meaningful for exploring special the emission wavelength of the luminescent materials.