Room Temperature Phosphorescence In Coordination Polymers Based On Non-aromatic Ligands

Molecule-based LLRTP(Long-lived Room Temperature Phosphorescent)has attracted much attention and research due to its long-lived luminescence observed at room temperature.The material can glow for a long time after removing the excitation light source,which makes it have potential application prospects in the fields of anti-counterfeiting,encryption and biological imaging.Many coordinate polymers(CP_S)exhibited LLRTP properties.However,the metal coordination polymers are usually composed of Zn²⁺,Cd²⁺and other heavy metals,which do great harm to the environment.Moreover,the emission color of RTP is relatively single,so there are still some problems in practical application.In this thesis,two CPs[Ca₅(AC)₁₀(DMSO)₂](1)=(AC^-=acetate,DMSO dimethyl sulfoxide)and[Ca(CH₂Cl COO)₂(H₂O)](2)with LLRTP were synthesized from common calcium ions and non-aromatic ligands.Trace organic aromatic guest molecules were doped into the compounds through in-situ synthesis,which successfully induced efficient color-tunable RTP emission The detailed work is as follows:(1)compound 1 was obtained by recrystallizing Ca(AC)₂ in DMSO solvent.1 has a green afterglow of about 4 s,which may be caused by the clustering of non-conventional chromophores.1 can also be used as a matrix for RTP induction of a variety of organic molecules by trace doping.A total of 18 organic aromatic compounds,including benzoic acid derivatives,naphthalene-carboxylic acid derivatives and naphthalene-imide derivatives,were doped to achieve the color adjustment from blue to orange of RTP,and achieve a longer RTP life.This work not only broadens the selection range of ligands for CP-type LLRTP materials and effectively avoids the use of heavy metal ions,but also achieves the multi-color RTP emission of non-conventional luminescence materials.These materials have application potential in high-end anti-counterfeiting.(2)Using chloroacetic acid as the ligand,compound 2 with LLRTP emission and higher quantum yield was prepared with the help of the introduction of chlorine which promotes intersystem crossing(internal heavy atom effect).Compared with 1,compound 2 as a host exhibits different luminescence induction effects on guest molecules.Eight composites were prepared and all shows high luminescence efficiency.The RTP of 1 and 2 can be attributed to the close-packed lattice of CPs which inhibit the non-radiative relaxation process of excited triplet states.On the other hand,the coordination of Ca²⁺can promote spin-orbit coupling,and the intersystem crossing from excited singlet state to excited triplet state.When the two compounds are used as the matrix,the organic aromatic guest molecules are captured through lattice defects.Their close-packed structure can effectively suppress the energy dissipation caused by the vibration and rotation of the guest molecules.The possible weak interactions between the matrix and the guest molecule is also one of the factors to achieve the efficient RTP emission.