Ionothermal Syntheses And Structural Characterizations Of The Metal-organic Coordination Polymers Constructed From Aromatic Carboxylic Acid Ligands

The metal-organic coordination polymers (MOCPs) have attracted much attention for their potential application in catalysis, separation, gas storage, optics,electrics and magnetics etc. The synthesis methods are important for achieving the predesigned MOCPs. In general, the MOCPs can be self-assembled from metal ions and multifunctional organic ligands in water or organic solvents (such as ethanol and DMF) (hydrothermal or solvothernal method). As"green solvent", the ionic liquids (ILs) are extensively used in the field such as separation and analysis, catalysis, organic synthesis. However, the research of MOCPs under iononthermal condition has emerged in very recent years. The structures and properties of the MOCPs obtained under ionothermal reaction are different from those of the MOCPs synthesized from traditional hydrothermal and solvothermal methods because of the unique physical and chemical nature of the ionic liquid solvents.In this thesis, we present the MOCPs constructed from the zinc ions, or cadmium ions, or cobalt ions, and aromatic acid, or sulfonate functionalized aromatic carboxylic acid organic ligands. Fortunately, eleven new MOCPs were successfully obtained under ionothermal reactions. The structures of all the compounds have been characterized by single-crystal X-ray diffraction, element analysis and IR spectroscopy. The thermal-gravity analyses have been performed on part of these compounds. We have discussed the effect of various factors including the effect of the ionic liquids, temperature, molar ratio of metal and ligand on the final structures. The thesis covers the following four parts:Chapter I: ReviewIn this part, the research background of the room temperature ionic liquids, and the concept and development of the metal-organic coordination polymers have been briefly introduced.Chapter II: Ionothermal syntheses and structural characterizations of the metal-organic coordination polymers constructed form aromatic carboxylic acid ligands.Five metalorganic complexes have been ionothermally synthesized. Compound {(PMIM)₂[Co₂(BTC)₂(H₂O)₂]}_n (1) contains dinuclear cobalt(II) units, which are linked by the trianionic 1.3.5-benzenetricarboxylate BTC^3- ligands to form a 3D [Co₂(BTC)₂(H₂O)₂]2n-n structure with (4·62)₂( 42·610·83) topology based on the BTC^3- and the Co₂ nodes. The 1-propyl-^3-methylimidazolium cation [PMIM]+ of the IL acts as extraframework charge-balancing species for the anionic [Co₂(BTC)₂(H₂O)₂]2n-n framework. Compound [Co3(BDC)3(IM)₂]_n (2) (IM = imidazole) features a 3D neutral framework with (412·63) topology constructed from unusual linear trinuclear Co3 as a secondary building block, which is linked by the dianionic 1,4-benzenedicarboxylate BDC2- ligands to form the final 3D structure. Compound {(H-IM)[Zn₂(BTC)(H-BTC)]}_n (3) features a 2D layered structure constructed from an unusual tetranuclear [Zn4(μ2-COO)6] cluster. The protonated imidazole acts as a counter ion for the anionic 2D layer. Compound {(EMIM)[Zn(m-phth)(IM)₂](BF4)}_n (4) has a 1D chain structure of [Zn(m-phth)(IM)₂] that formed from zinc ions and bridging isophthalate (m-phth2-) dianions. The 1-ethyl-^3-methylimidazolium cation [EMIM]+ and BF4- components of the IL both are incorporated into the final structure, which is a rare example of this kind of compounds. Compound [Zn(o-phth)]_n (5) has a 2D framework where the zinc ions are bridged by the phthalate (o-phth2-) dianions, containing a 2D [Zn(COO)]_n layer that constructed of carboxylate groups and zinc ions. It is interesting that there are 1D helical chains with opposite helicity in the 2D [Zn(COO)]_n sub-structure. The right- and left-handed helices are alternatively arranged with equivalent numbers.Chapter III: Ionothermal syntheses and structural characterizations of the metal-organic coordination polymers constructed form sulfonate functionalized aromatic carboxylic acid ligands.Six metal-organic complexes have been ionothermallly synthesized. {[Co(IM)6][Co₂(SIP)₂(IM)4]}_n (6) features an uncommon centrosymmetric imidazole cobalt cation [Co(IM)6]2+ and an anionic 1D chain structure of [Co₂(SIP)₂]_n2n- fromed from colbalt and 5-sulfoisophthalate (SIP^3-) ligands. Complex {(BMIM)₂[Cd₂(SIP)₂]}_n (7) has an anionic 2D layer containing unique tetranuclear [Cd₄(CO₂)6(SO₃)₂] cluster wherein the four Cd atoms are co-planar. The 1-butyl-^3-methylimidazolium cation [BMIM]⁺ of the IL acting as charge compensating agent intercalated into the [Cd₂(SIP)₂]_n2n- interlayers. Two homochiral enantiomers {(EMIM)[Zn(SIP)(IM)]}_n (8 and 9) obtained from spontaneous resolution under ionothermal reaction. Compound {(EMIM)[Zn(SIP)(IM)]}_n features a 3D [Zn(SIP)(IM)]_n anionic structure charged with 1-ethyl-^3-methylimidazolium cation [EMIM]+. In the 3D [Zn(SIP)(IM)]_n structure, the zinc ions are bridged by the SIP^3- ligand through its one carboxylate group and the sulfonate group to form a helical chain. Each helical chain is interacted with four neighboring helical chains through the Zn–O bonds where oxygen atoms come from the second carboxylate groups of the SIP^3- ligand, to give a 3D [Zn(SIP)(IM)]_n structure. The 3D [Zn(SIP)(IM)]_n structure has a chiral (10,3)-a topology. Compound [Na2(H-SIP)] n (10) has a 3D structure containing a 3D substructure constructed of sodium ions and carboxylate and sulfonate groups. Compound [Zn(SBC)(IM)] n (11) has a 2D structure where the zinc ions are linked by the carboxylate and sulfonate groups of the 4-sulfobenzoate SBC2- ligands.Chapter IV: Conclusion and perspectiveA brief conclusion and an outlook on this work are presented in this chapter.