Syntheses, Crystal Structures And Properties Of Novel Metal-organic Coordination Complexes With Carboxylate Ligands

Coordination polymers with interesting structures and special properties haveattracted great interest in crystal engineering and supramolecular chemistry, owing totheir considerable and potential applications in the fields of nonlinear opticalmaterials, magnetics, catalyst, biology and medicine, etc. The resulting structures withinteresting compositions and properties have been prepared through judicious choiceof ligand and center metal, as well as the synthesis conditions, such as temperature,solvent, pH value, template, and so on. Therefore, the kind of ligand, center metal andsynthesis condition are critical. The ligands with carboxylate groups have drawn greatattention for their strong coordination ability and versatile coordination modes. In thepast decades, rigid carboxylates have been widely studied. However, researches onflexible paraffinic carboxylates have been developed only in recent years probablydue to the difficulties in controlling the structures of the resulting complexes and thethermal stability.In this paper, we try to design and synthesize novel coordination polymers byusing rigid polycarboxylate ligand （5-Nitroisophthalic acid, H2NIPH） and flexibleparaffinic polycarboxylate ligand （1,2,3,4-butanetetracarboxylic acid, H4BTCA） withd-block transition metals, rare earth metal and alkali metal via diffusion method,solution method and hydrothermal method. Seven novel coordination complexes havebeen obtained:[Cd（NIPH）（imH）₂H₂O]_n·nH₂O （1）,[Cd₂（NIPH）₂（imH）₂（CH₃CH₂O）2]_n（2）,[Co（bpe）（NIPH）]_n（3）,[Co₂（BTCA）（H₂O）₆]_n·2nH₂O （4）,[Co₂（BTCA）（H₂O）₅]_n·2nH₂O （5）,[LaNa（BTCA）（H₂O）₃]_n·4nH₂O （6）, and[Na₂（BTCA）]_n（7）, respectively. The compounds have been characterized by singlecrystal X-ray diffraction analysis, elemental analysis and FT-IR spectrum. In addition,thermogavimetric analysis （TGA） has been taken on complexes1,2,5and6, as wellas fluorescent spectroscopy has been carried out on complexes1and2.Single crystal X-ray diffraction have revealed that complex1is a supramolecularstructure exhibiting1D zigzag chain pattern; complex2is also a supramolecularstructure displaying1D ladder-like double chain pattern; complex3has fivefoldinterpenetrated3D chiral structure; complex4is a3D structure with （4,4） layeredstructures; complex5is a supramolecular structure with（μ-aqua）bis（μ-carboxylate）Co（II） bridging units; complex6is a metal-organic framework （MOF） with pores in three kinds, additionally, only the smallest pores cantrap sodium cations; complex7is a3D framework with dinuclear structure.