Syntheses, Structures And Properties Of Metal Complexes Based On Carboxylic Acid Ligands

In the past decade, metal-organic frameworks （MOFs） attract people’s interest. Theyare new class of compounds between inorganic and material chemistry with potentialapplications. MOFs have been paid extensive attention due to the reasons as follows:1)The building blocks of metal and organic ligands are designable;2) They exhibit verycharming molecular topological networks with potential applications in various fieldssuch as gas adsorption, luminous property, magnetism, catalysis and nonlinear opticalproperties and so on.According to the crystal engineering method, several MOFs with new topologicalstructures have been synthesized solvothermally in this paper. Based on the research onthe structure, the possible properties have been discussed. In this paper, usingrigid/flexible carboxylic acid ligands, ten metal（II） complexes have been synthesizedand structurally characterized by single-crystal X-ray diffraction. Theirphotoluminescence and magnetism properties have been discussed. The main contentsin this paper were generalized as follows:1) The introduction section, introduced the definition of MOFs, their main synthesismethods and the potential application properties.2) we synthesized a novel hemi-rigid ditopic ligand, naphthalene-1,5-diyldioxy-diac-etic acid （H₂L1）, based on H₂L1and auxiliary N-donor ligands such asphenanthroline（phen） and2,2’-bipyridine（2,2’-bpy）, change the species of solvents（DMF, DMA and H₂O） and metal（II） ions, under solvothermal synthesis conditions, wegot five metal（II） complexes: Mn（L1）（DMF）（1）, Cd（L1）（H₂O）₂（2）, Pb（L1）（DMF）（3）,(Cd（L1）（phen）（4） and Cd₅（L1）₅（2,2’-bpy）2（5）. Complex1features a4-nodal（4,6）-connected three dimensional （3D） network with an unusual（4².6³.8）（4⁵.6）（4⁸.6⁶.8）₂topology, complex2exhibits a uninodal3-connected twodimensional （2D） framework with a （8².10） topology, complex3shows a2-nodal（3,4）-connected3D fsh-3,4-P21/c net with a （8³ï¼‰₂（8⁵.10） topology, complex4presents a2-nodal3D architecture with （4²Â·8⁴）-pts topology, and complex5shows a novel6-nodal（3,4,5,6）-connected3D framework with an unusual（4².6）2（4².8³.10）（4³.6².8⁵）₂（4³.6².8）₂（4⁵.6.8⁴）₂（4⁶.8⁷.10²ï¼‰ topology. L1^2-displays differentcoordination modes in the five complexes. Complexes1-3are hybrid metal oxidesbased on extended inorganic metal-oxygen-metal chains. H₂L1ligand has the preference for the formation of M-O-M linkage in the absence of N-donor. Complex1exhibits antiferromagnetic property and complexes2-5show differentphotoluminescence and photocatalytic properties.3) The flexible and achiral ligand, cyclohex-1-ene-1,2-dicarboxylic acid （H₂L2） wasprepared. Using H₂L2and auxiliary N-donor ligands such as phen and4,4’-bipyridine（4,4’-bpy）, change the species of solvents （DMF and H₂O） and metal（II） ions, undersolvothermal synthesis conditions, we got five metal（II） complexes:Zn（L2）（4,4’-bpy）·H₂O （6）, Cu（L2）（4,4’-bpy）0.5（7）, Cd（L2）₂（phen）₂（H₂O）₂·3H₂O （8）,Zn₅（L2）₄（μ₃-OH）（H₂O）₂（9） and Cd（L2）（H₂O）（10）. The structure of complexes6-10arecharacterized by single-crystal X-ray diffraction. Complex6shows a homochiralnetwork based on novel twisted hexanuclear cyclic unit, which are fused by sharingmetal ions into3D framework. Complex7exhibits2D framework constructed by1Dchain linked4,4’-bpy.4,4’-bpy exhibits twisted and planar conformations in complexes6and7, respectively. In complex8, alternating1D left-handed and right-handed helicalchains are observed. Complexes9and10display different2D frameworks based on Zn5unit and Cd-O-Cd infinite linkage, respectively. Complex6shows strong CD signal,and complexes7-10are achiral. The twisted4,4’-bpy plays an important role in theformation of the chiral complex6. The five complexes show different absorption andphotoluminescence properties as well as different thermal stability.