Syntheses, Structures And Near-infrared Luminescent Properties Of Series Of D-f Coordination Polymers

We synthesized twenty-seven new complexes by the hydrothermal,magnetic stirring,vibrating and microwave methods.In which,the lanthanide ions and the d¹⁰ (Zn²⁺ and Cd²⁺) ions were selected as the central metal ions,and the organic conjugated systems with carboxylate group were chosen as the main ligands.The single-crystal of these complexes was obtained and their structures were determined by the single-crystal X-ray diffraction.There includes six Cd-Ln complexes,Ln=Sm, Dy,Yb,Pr,Nd(two complexes);nine Zn-Ln complexes,Ln=Nd,Pr,Sm,Eu,Tb,Ho (two complexes),Dy(two complexes);six Ln-Ln complexes,Ln=Er,Yb(two complexes),Ho(three complexes);and six d¹⁰ metal complexes,Zn(two complexes) and Cd(four complexes).The IR and UV-Vis-NIR absorption spectra,excitation and emission spectra in the visible and near-infrared(NIR) region were determined,and analyzed with detail.The study of the luminescent properties of complexes was the emphases and the following results were summarized:(1) 4d-4f(Cd-Ln) coordination complexes:The Cd-Ln complexes are very difficult to be synthesized.Six Cd-Ln coordination complexes were obtained and they have excellent luminescent properties. Especially in the NIR region,the luminescent properties are special:the emission spectra have difference from the theoretical values and some reported complexes,that is,the characteristic f-f emission bands of Ln³⁺ ions present obvious shifts,broad and splittings.In the 4d-4f complexes,the Cd…Ln separation(3.6706～3.950(?)) is smaller. This is more feasible for the efficient d→f energy transfer and guarantees the sensitization of the d-block component to the f-block component.In addition,the interaction between the 4d orbitals of the Cd²⁺ ion and the 4f orbitals of the Ln³⁺ ion causes the intramolecular levels to be adjusted,which causes the emission bands to present shifts,broad and splittings.Maybe we can use it to design new d-f coordination complexes,in which the interaction between 4d orbitals and 4f orbitals cause the intramolecular levels to be adjusted.So we can obtain novel luminescent coordination complexes or materials with special emission bands. (2) 3d-4f(Zn-Ln) coordination complexesThe reports about Zn-Ln coordination complexes with unlimited structure are not many,and most of them use the shiff-base ligands.We select the pyridine-2,5-dicarboxylic acid and benzene-1,2,4,5-tetracarboxylic acid as ligands and synthesize six Zn-Ln coordination polymers with 1D chain structure and one Zn-Ln coordination polymer with 2D structure.They have good luminescent properties,and the d-block component(Zn-L section) can also sensitize the luminescence of Ln³⁺ ions.(3) The luminescent properties of the complexes are comparatively analyzed and assigned with detail.For the emission bands which have difference from the theoretical values or some reports,we first illustrate the shifts,broad and splittings of emission bands by the method of comparing and analyzing the relationship between the absorption spectra and the emission spectra,as well as the connection between the structure and the spectra.The satisfying results were received.(4) The Sm-Cd(1) and Sm-Zn(9) hetetronuclear complexes with NIR luminescent properties were first synthesized,and they were analyzed in detail.All the above works,the study of the d-f coordination complexes in particular, can provide important enlightenment and a new way to obtain a new type of luminescent material,especially in the NIR region,which has high efficiency and has the adjustable luminescent wavelength in relative free.