Studies On The Synthesis, Crystal Structures And Properties Of Complexes Based On Flexible Ligand 1, 4-Phenylenediacetate

In recent years, much attention has been paid to the complexes based on flexible ligands due to their versatile and novel structures and potential applications. 1, 4-Phenylenediacetic acid (H₂PDA) is one of the typical flexible ligands. It has two flexible acetates, resulting in trans- and cis-configuration. And the coordination modes of carboxylates are also complicated. So the complex structures based on H₂PDA are more versatile and novel. In order to research the relationship between their structures and properties, in this dissertation, we synthesized ten unreported transition metal complexes by liquid method. These complexes have been characterized by single-crystal X-ray diffraction, elemental analysis, IR. We also studied the thermal decomposition behaviors and other facet of some complexes among them.There are five chapters in this dissertation:In the introduction, I firstly introduce the research status of coordination polymers, and their potential applications in gas storage, selective catalysis, nonlinear optical and magnetism. Secondly, the study condition of H₂PDA is introduced concisely at home and abroad.In the second chapter, the synthesis, crystal structures and other properties of complexes [Cu(PDA)(2,2'-bpy)]·5H₂O(1),[Cu₂(PDA)_1.5(2,2'-bpy)₂](ClO₄)·5H₂O(2),[Zn₂(PDA)(2,2'-bpy)₂Cl₂](3),[Cd(PDA)_0.5(2,2'-bpy)Cl](H₂PDA)(4) and [Cd₂(PDA)₂(2,2'-bpy)₂]·2H₂O(5) which were synthesized by H₂PDA, 2,2'-bipyridine and transition metal salts are described. The complexes 1⁴ belong to Triclinic crystal system, P-1 space group. The central copper ions in complex 1 are six-coordinated with a distorted octahedral geometry; there are two kinds of copper ions in complex 2, one is five-coordinated with a nearly pyramid geometry, the other is six-coordinated with a distorted octahedral geometry; The central zinc ions in complex 3 is five-coordinated with a nearly pyramid geometry; The central cadmium ions in complex 4 are six-coordinated with a distorted octahedral geometry. The complex 5 belongs to Monoclinic crystal system, P2/c space group, the central cadmium ions are six-coordinated with a distorted octahedral geometry just like in complex 4.Complex 1 forms a 1D chain structure by coordination bonds and complicated hydrogen bonds andÏ€-Ï€stacking interactions make this complex a 3D supramolecular structure. In complex 2, H₂PDA with different coordination modes connect copper ions via coordination bonds to form a one-dimensional ladder-like chain. Abundant hydrogen bonds andÏ€-Ï€stacking interactions result in the formation of a 3D supramolecular structure. Complex 3 is a dimer andÏ€-Ï€stacking interactions play an important role in the formation of 3D supramolecular structure. Complex 4 and 5 both are 1D chain-like structures of cadmium, the difference is that in complex 4, Cd (II) ions are alternately bridged by PDA ligands and chloride ions into 1D chains but in complex 5 only PDA ligands act as bridge-ligand to connect Cd (II) ions together. In complex 4, there are free H₂PDA molecules and in complex 5 there are crystallographically independent water molecules. The hydrogen bonds andÏ€-Ï€stacking interactions make them form 3D supramolecular structures.In the third chapter, I describe the synthesis, crystal structures and other properties of complexes [Cu(PDA)(phen)]·2H₂O(6),[Cu(HPDA)₂(phen)(H₂O)](7),[Cu(PDA)(phen)₂]·(H₂PDA)(8),[Ni(PDA)(phen)(H₂O)]₂(9) which were synthesized by H₂PDA, 1,10-phenanthroline and corresponding metallic salts. The complexes 6 and 7 belong to Monoclinic crystal system, P21/c space group, and the central copper ions are both five-coordinated with a distorted pyramid geometry. Complex 8 belongs to Triclinic crystal system, P-1 space group and the central copper ions are six-coordinated with a distorted octahedral geometry. Complex 9 belongs to Monoclinic crystal system, P2(1)/n space group, the central nickel ions are six-coordinated with a nearly octahedral geometry.Complex 6 forms a 1D chain structure by coordination bonds and complicated hydrogen bonds andÏ€-Ï€stacking interactions result in the formation of a 3D supramolecular structure. Complex 7 and 8 both are mononuclear complexes, forming 3D supramolecules structures via hydrogen bonds andÏ€-Ï€stacking interactions. Complex 9 is a dimer and two Ni(â…¡) ions are linked by two PDA ligands with cis-configuration, resulting in a cyclic structure. The cyclic structures are linked one by one through hydrogen bonds into 1D chains andÏ€-Ï€stacking interactions between 1,10-phenanthroline molecules of adjacent dimer bring the formation of a 3D supramolecular network.In the fourth chapter, I describe the synthesis, crystal structure and thermal property of a coordination polymer [Cu(PDA)(DMF)](10). It belongs to Triclinic crystal system, P-1 space group and the central copper ions are five-coordinated with a nearly pyramid geometry. It is a two-dimensional square network with the caves'size being 11.608×12.134 (A|°). Thermogravimetric analysis indicates this complex have good thermal stability.In the fifth chapter, I summarize the achievements and defects systematically in the dissertation, and put forward proposals and expectations in the future.