Controllable Assembly And Properties Of Metal-organic Cage Complexes

As a new type of supramolecular crystal material,metal-organic cage complexes contain a stable hydrophobic cavity which has potential applications in host-guest recognition and catalytic conversion.However,the current strategy of constructing bimetallic cages through programmed methods is not explored well;the research on the assembly of mixed ligands to construct complex functional compounds is deficient.In this paper,several new types of bimetal-organic cages have been developed using subcomponent self-assembly strategies;functionalized mixed ligands have been introduced into the system to construct a new type of double-ligand bimetallic cage.A programmed method for the assembly of supramolecular systems with mixed metals or mixed ligands has been developed.By analyzing its host-guest and photoelectrochemical properties,the application in biology and energy will be expanded,which has practical significance.In the second chapter,two metal-organic cube(Cube-Ni,Cube-Pd)and one metal-organic triangular prism(Prism-Ni)based on tetra-aminophenylporphyrin were developed.The hexahedral structure creatively constructs two different metals in one supramolecular,which enriches the cage structure and optimizes the functional properties,and also provides new ideas for constructing heterometallic cages.Analyzing the spatial size of the porphyrin ligands,1,3,5-tris(4-aminophenyl)benzene was introduced into the system,and the tri-prism structure of bimetal and biligand was obtained through coordination-driven subcomponent self-assembly.This method provides a new idea for using mixed ligands to construct metal-organic polyhedra with better structure and properties.The host-guest behaviors between Cube-Ni and the substrate molecule anthracene were studied,and the 1:1 inclusion relationship of the host-guest was confirmed by UV-Visible differential spectroscopy and isothermal titration calorimetry.Cube-Ni is used as a catalyst oxidizes 86.7%of anthracene to anthraquinone under natural light at ambient temperature for 6hours,demonstrates high oxidation-reduction ability.A new metal-organic triangle is constructed by self-assembly of Schiff-base ligand L and iron(?),in which the robust coordination geometry consolidated by two orthogonal NOP chelators equips the triangle with high stability.The[3+3]structure Fe₃L₃ was characterized by high-resolution electrospray mass spectrometry.Fe₃L₃ was used as proton reduction catalyst to construct a supramolecular ternary photolysis hydrogen production system with fluorescein(Fl)as a photosensitizer,and triethylamine as an electronic sacrificial agent.The metal-organic triangle Fe₃L₃ exhibits excellent proton reduction ability in this system(ethanol/water(1:1,V/V),p H=11.0,300W xenon lamp),and the TON of hydrogen evolution reaches up to 645 in8 h.The high catalytic efficiency of Fe₃L₃ is attributed to the formation of host-guest species between the triangle and fluorescein,which shortens the spatial distance between Fe(II)and photosensitive molecules,and improves the efficiency of electron transfer in this system.