Synthesis And Properties Of Rare Earths Or Hydrogen Organic Framework Materials Based On Tetrathiafulvalenecarboxylic Acid Ligands

Tetrathiafulvalene?TTF?has been extensively studied as a?-electron donor in supramolecular systems.And the inherent electron-donating character of TTF derivatives has led to their use in the construction of highly efficient optoelectronic materials,optical sensors,and electron-transfer ensembles.TTFs are also promising candidates for the development of the so-called“functional materials”that might see use in many fields.In this paper,tetrathiofulvalene carboxylic acid derivatives are used as structural units to assemble rare earth ions or organic bipyridine compounds to synthesize corresponding metal-organic or hydrogen-bonded organic framework materials.The redox properties,magnetic properties,stability and electrical conductivity of these frame materials were systematically studied.A series of isomorphic three-dimensional MOFs?1-5?were synthesized by solvothermal method using the synthesized TTF carboxylic acid ligand and Ln?NO₃?₃·6H₂O?Ln=Eu,Gd,Tb,Dy,Er?rare earth metal salts.Electrochemical test shows the redox-activity of these MOFs.Therefore,the above MOFs material is further chemically oxidized to obtain the oxidized MOFs?6-10?.Thermogravimetric tests show that the thermal stability of all MOFs material reaches about 310°C.Solid UV testing and calculations show that the oxidized MOFs have smaller semiconductor band gap values.5 shows a smaller electronic conductivity because the distance between adjacent S···S in the structure is longer.The magnetic test suggesting ferromagnetic interactions existed in 3,4,5 and the corresponding oxidized 8,9,10 structures,and they exhibited slow magnetic relaxation behavior in the applied field.4 and 9 show field-induced magnetic behavior of single-molecule magnets with effective energy barriers(U_eff)of 30.769 K and 26.41 K,respectively;the values of?₀ are5.23×10^-88 and 1.04×10^-88 s,respectively.Two hydrogen-bonded organic framework materials?HOFs??11 and 12?were synthesized by solvothermal method using the synthesized H₄TTF-TB ligand and bispyridine ligands?Bpa and Bpp?.In the two structures,the carboxylic acid and pyridine form a strong hydrogen bond,and the carboxylic acid in the structure of 11 also forms hydrogen bond with ethanol molecule.The structure of 12 has the regular pore structure and the thermal stability is about 200°C.Solid ultraviolet and electronic conductivity tests show that 11 and 12 have typical semiconductor characteristics,and the electrical conductivity is 1.58×10^-88 S cm^-11 and2.48×10^-8S cm^-1,respectively.The proton conductivity of 12 at 60°C and 98%relative humidity is 2.18×10^-7S cm^-1,and the activation energy is 0.047 eV,which belongs to the Grottuss conduction mechanism.