Construction And Luminescent Properties Of Donor-acceptor Materials Based On Coordination Polymer Host-guest Platforms

As a new inorganic-organic hybrid functional material formed by combining metal ions and organic ligands through coordination bonding,coordination polymer(CP)has shown great potential in the fields of gas adsorption and separation,catalysis,sensing,drug mitigation,optoelectronic magnetic materials and energy storage due to its unique composition diversity,structural designability and adjustable porosity.It highlights the great potential.In recent years,the use of CP as a host platform to introduce rich interaction sites in its pores,disperse,immobilize or stabilize the guest species,and construct highly tunable donor-acceptor optoelectronic materials has become a hot research topic in chemistry and materials-related fields.New features such as electron/energy transfer,redox reactions or other processes induced by host-guest synergy often can occur in host-guest coordination polymers,and thus have promising applications in the field of donor-acceptor optoelectronic materials.In this study,dipyrido[3,2-a:2’,3’-c]phenazine(dppz)containing electron-deficient units was selected as the main ligand,and the components and structures of the complexes were modulated by changing the metal ion centers and auxiliary linking ligands,and three new host-guest coordination polymer platforms with highly tunable properties were designed.On this basis,31 donor-acceptor luminescent materials were synthesized by introducing different electron-rich guests by the "one-pot method",and their structures and stability were characterized and analyzed by single crystal diffraction,powder diffraction,thermogravimetric testing and other characterization methods,and their luminescence properties were studied in detail.The main studies are as follows.(1)The first type of host-guest platform(HGP1)with electron-deficient units was constructed by chelating and ligating dppz with Cd2+ and rigid p-phenylene dicarboxylic acid(PTA)as an auxiliary linking ligand.Thirteen donor-acceptor complexes were synthesized by introducing different electron-rich guest molecules such as naphthalene,anthracene and pyrene in the solvothermal reactions of the ligands with metal ions.Structural analysis showed that the main framework of the system is a one-dimensional chain intertwined structure and is capable of adaptive adjustment according to the guest size.The performance study showed that HGP1 exhibited significant guest-dependent fluorescence emission in the visible region(493-660 nm)due to the strong charge transfer effect generated by the close stacking of the donor molecule and the acceptor phenazine framework.(2)The second type of host-guest platform(HGP2)was constructed by selecting lanthanide ions with high coordination number(Ln3+ = Tb3+,Sm3+,Gd3+,Dy3+)with dppz as the primary ligand and rigid PTA as the secondary ligand.Nine donor-acceptor complexes were synthesized using a similar "one-pot method" approach to introduce the guest molecules.Unlike HGP1,the HGP2 materials are all one-dimensional isostructural with binuclear metal clusters linked by dicarboxylic acid ligands.By introducing rare-earth ions to modulate the structure,this series of materials exhibited a wider tunable fluorescence emission(478-660 nm).(3)The rigid PTA ligand in HGP1 was replaced by 2,2’-biphenyldicarboxylic acid(H2dpdc)with flexibility to construct the third class of flexible host-guest platform(HGP3).With pyrene as the guest molecule representative,six donor-acceptor ligand polymers with different modes of pyrene stacking and contents were obtained by precisely regulating the amount of each solvent component in the reaction system.Due to the freely rotatable single bonds in H2 dpdc,the main framework of this series of complexes exhibits a zero-dimensional to two-dimensional structural change,which effectively regulates the stacking pattern and content of the guest pyrene molecules,and thus achieves effective regulation of the luminescence properties of the same host and guest components(533-635 nm).Meanwhile,three similar complexes were obtained by introducing guest molecules such as perylene,and the selectivity of HGP3 for the size of the guest molecules was investigated.