Syntheses,Structures And Properties Of Coordination Polymers Derived From Semirigid Ether-linked Polycarboxylic Acids

Coordination polymers based on semirigid polycarboxylate ligands have currently attracted considerable attention because of their intriguing structural topologies and their potential applications as functional materials in magnetism,luminescence,chemical sensors,and so on.The two benzene rings of semirigid tricarboxylate ligand can appropriately rotate around the central oxygen atom and the carboxylate groups of them can be completely or partially deprotonated which can result in diverse coordination patterns and high dimensionalities,especially when acting as a multiply bridging space.They can lead to the appearance of new crystalline materials with new structures.Hence,in the present work,two asymmetric semirigid tricarboxylate ligands and four asymmetric semirigid tetracarboxylate ligands were employed to assemble Mn(?)ion and d10 configuration(Zn(?)or Cd(?))ions into fourteen coordination polymers with the help of auxiliary ligands.They were characterized by IR spectroscopy,elemental analysis(EA),single-crystal X-ray diffraction,thermogravimetric analysis(TGA)and powder X-ray diffraction(PXRD).The magnetic properties of Mn(?)complexes have been studied in detail.The luminescent properties of Zn(?)or Cd(?)complexes were also studied in detail.The complexes with d10 configuration ions were used to probe small molecules and metal ions.Quenching mechanisms have been studied deeply herein.The detail of studies are listed as follow:(1)A new porous three-dimensional framework with chemical formula of [Cd3(L1)2(phen)3]n·5n H2O(1)(H3L1 = 2-(4-carboxyphenoxy)terephthalic acid & phen = 1,10-phenanthroline)has been synthesized.The 1,as a potential material of the sensing application,has an uncommon 3D microporous structure in which the trinuclear [Cd3(phen)3(?2-COO)4]2+ SBUs are inter-connected by the semirigid L13-ligands.The 1 has good stabilities not only in aqueous solution in the range of p H = 1.0-14.0 but also in solid from room temperature(RT)to 330 ?.Fluorescence titration,cyclic and anti-interference experiments demonstrate that the 1 is an excellent probe for volatile organic ketones(acetone/2-butanone)and hexavalent chromate(Cr O42-/Cr2O72-)in aqueous solution.The luminescence investigations in aqueous solution of p H = 9 reveal that the 1 can efficiently and selectively detect Cr O42-/Cr2O72- anions without the interference of other metal cations.Quenching mechanisms are also studied in detail.(2)Synthesis of 2 was similar to that of 1 except that 1,10-phenanthroline(phen)was replaced by 4,4'-bipyridine(4,4'-bpy).The 2 presents a two-dimensional(2D)structure based on the dinuclear Cd(?)secondary building units with fes topology type and the vertex symbol of(4.82).The 2 with high thermo-stability,solvent-stability displays a good luminescence in aqueous solution.The experimental data highlight the 2 as a sensor for Cu2+ ions with high efficiency and sensitivity.The luminescence investigations also reveal that 2 can efficiently and selectively detect Cr O42-/Cr2O72- among eleven anions.Importantly,it can be regenerated by a fast and simple method in detecting these ions.(3)Solvothermal reactions of Zn(?)or Mn(?)ions and 2-(4-carboxyphenoxy)terephthalic acid(H3L1)in the presence of N-heterocyclic group ligands(1,10-phenanthroline(phen)or 1,4-di(1H-imidazol-1-yl)benzene(bib)or 4,4'-bipyridine(4,4'-bpy))produced four multi-dimensional coordination polymers 3~6.The 3 features one-dimensional double ladder formed by syn-anti carboxylate-bridged dimeric Mn(?)units and gives the(42.6)topology.The 4 is formed by linear Mn(?)inorganic chains connected to each other by two symmetry independent HL12- ligands as well as coordinated bib bridges giving rise to a three-dimensional net.The 5 exhibits two-dimensional layer structure containing dinuclear Zn(?)units.The phen and benzoic acid groups are like two kinds of blades in the two sides of the two-dimensional structure of 5.The 6 is an interesting three-dimensional network including tetranuclear tricyclic [Zn4(OH)2(COO)6] clusters.The semirigid tricarboxylate ligand(H3L1)shows three geometric modes in the self-assembly of four coordination polymers: a)'L' shape in 3;b)'I' shape in 4 & 5;c)'T' shape in 6.The magnetism disclosed their antiferromagnetic behaviors of 3 and 4.The 5 and 6 feature well solvent stability and can withstand ten common solvents.The luminescence exploration demonstrated that the complex 5 had highly sensitive,selective,low detection limit and well-recyclable properties in the detection of Cr O42-/Cr2O72- anions in aqueous solution.Quenching mechanisms were also studied in detail.(4)Syntheses of 7~10 were similar to that of 3~6 except that 2-(4-carboxyphenoxy)terephthalic acid(H3L1)was replaced by 4-(4-carboxyphenoxy)isophthalic acid(H3L2).The 7 and 8 present two-dimensional(2D)structures based on the dinuclear Mn(?)secondary building units with the vertex symbols of(4.82)and(32.44)(34.46.64.7),respectively.The 9 possesses one-dimensional(1D)structure and reveals a uninodal 2-connected chain with the 2C1 topology.The 10 exhibits a 1D ladder-like double chain,containing a 1D metal–organic chain interconnected by the 4,4'-bpy ligand with the vertex symbol of(42.6).Such a rich structural diversity of 7~10 is driven by various factors,including the type of the metal(?)ions and the ancillary ligands,as well as the coordination mode of ligand.The 7 and 8 show antiferromagnetic interactions in dimeric units that are related to double syn-anti carboxylate bridges and four bis-bidentate carboxylate groups with syn-syn and ?2-oxo modes.The solid-state luminescent behaviors of 9,10 were also investigated systematically.(5)A series of Mn(?)coordination polymers 11~14 have been prepared with 1,4-di(1H-imidazol-1-yl)benzene(bib)as the main ligand and four asymmetric semirigid tetracarboxylate ligands 3-(2,4-dicarboxyphenoxy)phthalic acid H4L3,3-(2,5-dicarboxyphenoxy)phthalic acid H4L4,4-(2,4-dicarboxyphenoxy)phthalic acid H4L5,4-(2,5-dicarboxyphenoxy)phthalic acid H4L6 as coligands.Single-crystal X-ray diffraction studies reveal that the 11 and 12 are 2D-layer frameworks with similar Mn(?)-oxygen inorganic magnetic chain's sequence-J1J1J2-.The 13 and 14 contain similar tetranuclear Mn(?)clusters with different dimensional frameworks.In 13,each tetranuclear Mn(?)clusters is coordinated to neighboring clusters by L54– and bib ligands and extends into a microporous framework,six-membered water clusters fill into the cavities.But,in 14,each tetranuclear Mn(?)clusters are linked by L64-and bib ligands into 2D layer.Magnetic investigations indicate that these coordination polymers all show weak antiferromagnetic coupling between the adjacent Mn(?)ions.Magnetostructural analyses based on the data of 11~14 imply that the magnitude of the magnetic coupling has some relationship with the Mn…Mn distance and the number of carboxylate bridges.