Syntheses And Luminescent Properties Of Copper Cluster-Based Coordination Polymers Based On A Flexible Multidentate Ligand

Metal-cluster-based coordination polymers have attracted more and more attentions and researches,attributing to their structure diversity and flexibility,controllable pore size and shape,high porosity,open active site and large specific surface area.Among them,the copper-cluster-based coordination polymers exhibit excellent luminescent intensity and stability and rich coordination geometries.In addition,copper-cluster-based coordination polymers have a variety of stimuli-responsive behaviours,such as,thermochromism,vapochromism/solvatochromism,and mechanochromism.By using flexible multidentate ligands to react with copper iodide,the coordination polymers with multi-stimuli-responsive performance and different copper units,were successfully obtained.Firstly,two three-dimensional quadrangular-prismatic coordination polymers based on{Cu₃I₃S}cluster,{[Cu₃I₃(TPSA)]·DEF}_n(1)and{[Cu₃I₃(TPSA)]·DMF}_n(2),were prepared by adjusting the solvents(DEF and DMF).The proportions between two emission bands about two copper cluster-based coordination polymers can be adjusted by different solvents,resulting in different luminescence of the two compounds:1 shows an orange-yellow fluorescence,while 2 shows an UV-excited white emission.Combining the stimuli-responsive properties of copper cluster and metal-organic framework,compounds 1 and 2 display multi-stimuli-responsive behaviours,which can simultaneously respond to temperature,solvent and nitro-explosives with tunable color or intensity.We further investigated the mechanisms of solvent regulation and stimuli-response.Secondly,by adjusting the ratio of ligand and cuprous iodide,the coordination polymer{[(Cu₃I₃)₂(Cu₄I₄)(TPSA)₄]·CH₃CN}_n(3)was obtained.The coordination polymer rarely traps thevertex-missing-cubane{Cu₃I₃S}cluster and crown-shaped{Cu₄I₄}ring in the same lattice to form a 3,4,4,6-connected topological network based on the metal cluster and metal ring.Through structural analysis,we believe that the flexible multi-dentate ligand TPSA can adopt different conformations and different coordination modes,which is the main reason for the formation of this special structure.The complex displays a red emission at room temperature and shows a thermochromic behaviour,suggesting the potential to be a luminescent ratio thermometer.