Preparation And Application In Polymer Light-emitting Diode Of Ln³⁺-Containing Metallopolymers With Near-infrared Luminescence

In consideration of the potential applications of Ln³⁺-centered(Nd³⁺,Yb³⁺,Er³⁺,etc.)near-infrared luminescence in optical communication,night vision,biological imaging and medical treatment,there has an urgent requirement of organo-Ln³⁺hybrid materials with excellent photo-physical property.In this thesis,two series of PVK-supported hybrid materials grafted from bis-benzimidazole-Ln³⁺and Schiff-base-Ln³⁺complexes were obtained,respectively,where besides excellent near-infrared luminescent performance,their high thermal stability,good mechanical strength and film-forming were also realized.Moreover,using the selected PVK-supported hybrid material as the light-emitting layer,polymer light-emitting diode（NIR-PLED）with Ln³⁺-centered(Nd³⁺,Yb³⁺,Er³⁺,etc.)near-infrared luminescence was developed.Firstly,through the self-assembly of theβ-diketone organic ligand HL¹（HL¹=（Z）-3-methyl-1-phenyl-4-（2,2,2-trifluoro-1-hydroxyethylidene）-1H-pyrazol-5（4H）-one）,the bis-benzimidazole ligand 4v-bpbim（4v-bpbim=1-（4-vinylbenzyl）-5-（1-（4-vinylbenzyl）-2-（pyridin-2-yl）-1H-benzo[d]imidazol-5-yl）-2-（pyridin-2-yl）-1H-benzo[d]imidazole）and LnCl₃·6H₂O（Ln=La,Nd,Yb,Er,Gd）,series of dinuclear while vinyl-modified complex monomers[（4v-bpbim）Ln₂（L¹）₆]（Ln=La,1;Nd,2;Yb,3;Er,4;Gd,5）were obtained,respectively.Moreover,further based on their copolymerization with NVK（N-vinylcarbazole）in the presence of AIBN（2,2-azobisisobutyronitrile）,series of PVK-supported metallopolymer-type hybrid materials Poly（NVK-co-[（4v-bpbim）Ln₂（L¹）₆]）were afforded,respectively.Furthermore,besides the characterization of elemental analysis（EA）,¹H NMR,FT-IR and GPC,the photo-physical properties of complex monomers 1-5 and their metallopolymer-type hybrid materials were also explored.The results showedt_Nd=4.12ms andФ_Nd^L=0.47%for complex 2,t_Yb=22.86ms andФ^L_Yb=0.98%for complex 3 andt_Er=7.33ms andФ_Er^L=0.008%for complex 4,respectively.In contrast,for the metallopolymer-type hybrid materials Poly（NVK-co-[（4v-bpbim）Ln₂（L¹）₆]）（200:1）,the significantly improved NIR luminescence oft_Nd=6.69ms andФ^L_Nd=0.52%for Poly（NVK-co-2）,t_Yb=38.35ms andФ^L_Yb=1.11%for Poly（NVK-co-3）andt_Er=19.83ms andФ_Er^L=0.19%for Poly（NVK-co-4）,respectively,was realized.Secondly,based on the self-assembly of the complex precursor of[Zn（L²）（4vp）]（H₂L²=N,N’-bis（salicylidene）-1,2-diamine,4vp=1-（chloromethyl）-4-vinylbenzene）,theβ-diketone HL¹ and LnCl₃·6H₂O（Ln=La,Nd,Yb,Er,Gd）,the series of hetero-dinuclear complex monomers[Zn（L²）（4vp）Ln（L¹）₃]（Ln=La,6;Nd,7;Yb,8;Er,9;Gd,10）were obtained,respectively.Especially,based on the X-ray single crystal diffraction（XRD）analysis of the representative complex monomer[Zn（L²）（4vp）Gd（L¹）₃]（10）,the bridging of the five-coordinate Zn²⁺ion and the eight-coordinate Gd³⁺ion leads to the formation of a stable Zn²⁺-Gd³⁺-heterobinuclear structural framework.Meanwhile,the photophysical properties of[Zn（L²）（4vp）Ln（L¹）₃]（7-9）are as follows:7:t_Nd=2.98ms andФ^L_Nd=0.58%;8:t_Yb=26.82ms andФ^L_Yb=1.04%;9:t_Er=16.36ms andФ^L_Er=0.01%.Finally,through the copolymerization of one of the complex monomers[Zn（L²）（4vp）Ln（L¹）₃]（Ln=La,6;Nd,7;Yb,8;Er,9;Gd,10）with NVK,the series of PVK-supported metallopolymer-type hybrid materials Poly（NVK-co-[Zn（L²）（4vp）Ln（L¹）₃]）（Ln=La,6;Nd,7;Yb,8;Er,9;Gd,10）were obtained,respectively.In dependence of their characterization and photo-physical property,at a feeding molar ratio of 75:1,Poly（NVK-co-7）givest_Nd=7.14ms andФ_Nd^Nd=0.71%,Poly（NVK-co-8）givest_Yb=31.86ms andФ_Yb^L=1.34%and Poly（NVK-co-9）givest_Er=20.12ms andФ^L_Er=0.20%,respectively.Especially,using Poly（NVK-co-[Zn（L²）（4vp）Yb（L¹）₃]）（75:1）as the light-emitting layer,NIR-PLED was designed,and the performances of the turn-on voltage at 9 V,the maximum eternal quantum yields（EQE）of 0.049%and the maximum irradiance is 78.68mW/cm² at 16 V,were realized,respectively.