Synthesisf, Structure And Propetries Of Novel Indium(Ⅲ) Coordination Polymers

Coordination polymers as novel functional materials have attracted more andmore attentions because of their unique structural features, rich topologies andpromising applications in gas adsorption, ion-exchange, catalysis and chiral separation.With the innovation of the synthesis technology and the continuous progress of theanalytic method, a large number of functional coordination polymers with novelstructures have been synthesized. So far, the research object of coordination polymershave been involved in most of the metal ions in the periodic table, but mostconcentrations were focused on transitional divalent metals and rare earth metals,relatively few studies on main group metals. Recently, the third main group elementindium cation attracts more and more attentions owing to its fantastic coordinationproperty which has the ability to adopt MO₆, MO₇, or even MO8coordination modes.As heterogeneous lewis acid catalysts, they have the advantages of low toxicity andhigh selectivity which can make a variety of organic reactions carry out smoothlyunder mild conditions. This is in line with the requirements of green chemistry andshows a good prospect.According to the principle of molecular engineering, we have focused our study onexploring new functional materials, and mainly studied the syntheses, structures andthe properties of these materials, in order to investigate the structural diversity of coordination polymers and the relationship between the structure and the property.The syntheses of coordination polymers can be influenced by many factors, and it ischallenging to achieve the target of directed synthesis. In order to achieve this goal asquickly as possible, we have conducted a series of exploratory experiments, andaccumulated the original experimental data to enrich the theoretical model. In thispaper, we selected different types of organic carboxylic ligands as linkers to constructa series of indium coordination polymers under hydrothermal or solvothermalconditions. In addition, we also explored the impact of different factors on productsduring the synthesis process and discussed their structures and properties in detail.These results will be introduced from the following four issues:(1) We selected rigid1,3-isophthalic acid (1,3-H₂BDC) and1,4-naphthalene acid(1,4-H₂NDC) as organic ligands to construct four indium coordination polymers[In₂(OH)₂(1,3-BDC)₂(2,2'-bipy)₂](1), HIn(1,3-BDC)₂·2DMF (2), In(OH)(1,4-NDC)·2H₂O (3) and HIn(1,4-NDC)₂·2H₂O·1.5DMF (4) under hydrothermal orsolvothermal conditions. Among them, compound1contains double-chain-likeribbons which are constructed by [In₂(OH)₂(2,2'-bipy)₂]∞2+dimeric units and1,3-BDC ligands by introducing the second ligand2,2'-bipyridine. This kind of dimericunits is first reported in indium coordination polymers. In compound2, the InO6octahedra which be regarded as4-connected building unit can connect with1,3-BDCto form2D sql topology under solvothermal conditions. This kind of building unit isalso first occurred in indium coordination polymers. Finally, compound1and2form3D supramolecular structures through Ï€-Ï€ interactions. Compounds3and4exhibit3D networks by introducing1,4-NDC as organic ligand under different solvothermalconditions. Compond3contains two kinds of square shape channels and forms SrAl2topology; Compound4possesses2-fold interpenetrating dia topology, and it is thefirst example of2-fold interpenetrating diamond net only based on rigid1,4-NDCligand. The syntheses of compounds1-4proved that the solvent effect plays animportant role on preparing new indium coordination polymers.(2) We selected flexible1,4-phenylenediacetic acid (1,4-H₂pda), trans-1,4-cyclohexanedicarboxylic acid (1,4-H₂chdc) and4,4'-oxybisbenzoic acid (4,4'-H₂oba) as organic ligands to construct three indium coordination polymers(Me₂NH₂)[In(cis-1,4-pda)2](5), In(OH)(trans-1,4-chdc)(6) and In(OH)(oba)·DMF·2H₂O(7) under different solvothermal conditions. Compound5displays a novel1Dno-planar double chain. Although a mixture of cis-and trans-1,4-H₂pda was used, theproduct of compound5is a single phase with only cis-pda^2-ligands. Cmpounds6and7are formed3D networks by the infinte-In–OH–In–OH-rod-shaped secondarybuilding unit. In cmpound6, the1,4-chdc2-ligands show two types of conformation:e,e-trans-and a,a-trans-form by connecting the rod-shaped secondary building unitsto form a long and narrow rhombus-shaped channel; while in cmpound7, therod-shaped secondary building units exhibit two types of packing arrangements,parallel and vertical, moreover, the latter is first occurred in coordination polymers.The syntheses of compounds5-7are to investigate the impact of differently flexibledicarboxylic acid ligands on the structures of the final products.(3) Recently, the synthesis of chiral low-connectivity (3-or4-connected)coordination polymers attracts special attention on accounts of their appealingarchitectures and high surface areas. We have tried to go on tentative test in this field.Finally, using D-H₂Cam as organic ligand we synthesized a new chirallow-connectivity indium coordination polymer InH(D-C₁₀H₁₄O₄)₂(8). In compound8, each D-Cam2-ligand connects the adjacent indium ions into a helical chain withthe same left-handed helical orientation. The adjacent chains run parallel to each otherand are interconnected by D-Cam2-ligands to generate a3D anionic chiral network[In(D-C₁₀H₁₄O₄)₂]n-with dia topology.(4) The nitrogen-containing heterocyclic carboxylic acid ligands have attractedmuch attention because of their strong coordination ability of N and O atoms whichcan build more innovative topologies. We also explored the synthesis reactionsbetween indium and nitrogen-containing heterocyclic carboxylic acids, and selected2-pyridinecarboxylic acid (2-HPDC) and2,3-pyrazinedicarboxylic acid (2,3-H₂PDC)as linkers to prepare two indium coordination polymers In₂(OH)₂(2-PDC)₄(9) andHIn(2,3-PDC)₂(10) under different solvothermal conditions. Compound9exhibits1Dsupramolecular structure which is formed by Ï€-Ï€ interactions among dinuclear In₂(OH)₂(2-PDC)₄molecules; In compound10, the InO6N2octahedra connected with2,3-PDC2-to exhibit3D nbo topology.The solid-state fluorescence spectroscopy showed compounds1-7,9-10displayintense fluorescent emissions, so they may be suitable as excellent candidates ofphotoactive materials. In addition, the gas adsorption properties of compounds3,4,6and8were tested.In this paper, we selected different types of carboxylic acid ligands to construct aseries of indium coordination polymers under hydro(solvo)thermal conditions, andstudied the impact of different factors on the final products in the synthesis process. Inaddition, we studied the potential applications of these compounds in optics as well asgas storage. These will not only enrich the coordination chemistry of indium, but alsoprovide theoretical basis for the ultimate realization the directed synthesis of suchcompounds.