Syntheses And Structures Of Silver Coordination Polymers Based On Ethynide Ligands And Aromatic Multicarboxylic Acids

As is well-known, silver(I) ion principally exhibits linear, trigonal, squareplanar, square-pyramidal, trigonal-bipyramidal, tetrahedral, and octahedral coordination geometries and is apt to form short Ag…Ag contacts, which brings the5s,5p and4d orbitals into close proximity in the energy level diagram. Due to above-mentioned characteristics of Ag(I), silver-containing coordination polymers have attracted unprecedented interests not only because of their intriguing aesthetic structures but also because of their interesting luminescent, electronic properties. A series of silver-ethynide complexes containing aromatic ring are obtained by changing the number of the alkynyl group and the substituted group. On the basis of our previous studies and the important role of aromatic multicarboxylic acid ligands, herein, we focus on the self-assembly of silver(I) and multicarboxylic acid under differet conditions and obtained thirteen new silver-organic frameworks. In addition, the single crystal structure analysis, spectral analysis and luminescent properties of compounds were also investigated.This work includes the following two parts:Ⅰ. Assembly of silver-ethynide coordination polymers.(1) Through changing the length of pendant arms, three new ligands have been synthesized. Those ligands bearing terminal ethynide moieties attached to benzene skeleton have been used in the syntheses of three silver-ethynide complexes (1-3). In [(AgL1)(AgCF3CO2)3]n (1), butterfly-shaped Ag4baskets are united together by trifluoroacetate groups to lead to a layer structure, which is also consolidated by silverearomatic interactions, adjacent layers are then linked into a threedimensional supramolecular architecture through weak C-H…F hydrogen bonding. In {[(AgL2)(AgCF3CO2)6(H2O)2](H2O)6}n (2), ladder-like chains are associated into three-dimensional supramolecular architecture through a rich hydrogen bonding system. In [(AgL3)·(AgCF3CO2)5(H2O)]n (3), square-pyramidal Ag5baskets are also fused together by the trifluoroacetate groups with the assistance of argentophilic interactions and silver-aromatic interaction give rise to a2D coordination network, which are further united by C-H…π interaction to produce a three-dimensional supramolecular framework.(2) A series of four new ligands bearing terminal ethynide moieties attached via changing the number of pendant arms to benzene skeleton have been used in the syntheses of four silver-ethynide complexes (4-7). In {(Ag2L4)2-(AgCF3CO2)10·(CH3CN)2·(H2O)4·(μ2-H2O)2]·(AgBF4)}n (4), Ag15aggregates are associated together by argentophilic interaction and interchain hydrogen bonds to give rise to a2D network, respectively. In [(Ag2L5)-(AgCF3CO2)7·(CH3CN)-(H2O)]n (5), butterfly-shaped Ag4baskets are connected into silver(I) columns, which are further linked by external Ag(CF3COO)2units, argentophilic interactions and face-to-face aromatic π-π interactions into a3D metal-organic framework. In {[(Ag2L6)-(AgCF3CO2)10·(CH3CN)6·(H2O)2-(OH)2]·(H2O)}n (6), Ag6-phenyl ring-Ag6structural units are interconnected by a pair of μ4-η2,η2trifluoroacetate groups and hydrogen bonds to produce a3D metal-organic network, respectively. Two kinds of silver rods in parallel orientation are bridged by three μ3-η1,η2and one μ4-η2,η2trifluoroacetate groups to generate a two-dimensional metal-organic network of [(Ag3L7)2-(AgCF3CO2)13·(CH3CN)5-(H2O)]n (7), in which the trianion exhibits the unprecedented μ20-coordination mode.(3) Through changing the substituent on aromatic ring, complexes8-12were obtained. In complexes [(AgL8)·(AgCF3CO2)2]n (8)[(AgL8)·(AgCF3CO2)5·(CH3CN)·(H2O)]n (9),[(AgL8·(AgCF3CO2)3·(bpy)2]n (11),�'�[(AgL9)·(AgCF3CO2)4]n (12), silver(Ⅰ)-aromatic interactions play important roles in assembling a series of silver-organic frameworks. Notably, an unusual π…Ag4…π sandwich unit makes it appearance in complex9, which is the first example in silver-ethynide complexes. By introducing nitrogen-donor ancillary ligands to the silver-ethynide system, complex [(AgL9)2·(AgCF3CO2)3]n (13) was obtained.Ⅱ. Silver-organic frameworks based on rigid aromatic multicarboxylic acid ligands.(1) The reactions of1,2,3-benzenetricarboxylic acid ligand and silver nitrate/silver oxide in the presence of N-containing auxiliary ligand4,4’-bipyridine under hydrothermal or solvent evaporation conditions yielded two unusual coordination complexes (14and15). Complex{[Ag2(Hbtc)(bpy)2](H2O)2}n (14). features an infinite1D�'1D tubular intertwinement network, while complex {[Ag3(btc)(bpy)3(H2O)](H2O)7}n (15) exhibits a double ladder structure which contains rare winding water chains. Both infinite1D�'1D tubular chains in complex14and double ladder in15are mutually interconnected by hydrogen bonding and π-π stacking interactions into three-dimensional (3D) supramolecular networks.(2) Using1,2,3,4-benzenetetracarboxylic acid (H4mpda) instead of1,2,3-benzenetricarboxylic acid, four silver-organic coordination polymers (16-19) are obtained. In recent years, many MOFs with two or more polymeric substructures in the crystalline state have been reported, which usually occur in an interpenetrating fashion. Complexes [Ag4(mpda)]n (16),{[Ag2.5(mpda)(bpy)2]·[Ag(bpy)]·[Ag(bpy)(H20)]·(NO3)0.5·(H20)9}n (17),{[Ag5(mpda)2(bpy)4]·[Ag(bpy)]·[Ag(bpy)(H2O)]·[Ag(bpy)(H2O)]·(H2O)16}n(18), and {[Ag2(mpda)(H2O)]·[Ag(bpy)]·[Ag(bpy)]}n (19) exhibit a coordination polymer containing three or four independent structural motifs in a single crystal structure.(3) In continuation of our research program,1,2,3,4-benzenetetracarboxylic acid (H4mpda), and1,2,3,4,5-benzenepentacarboxylic acid (H5bpca) ligands were used to constructed silver-organic frameworks (20and21). Organic anion template-controlled reactions of benzenepolycarboxylic acids with silver(I) salts resulted in two coordination polymers with distinct structural features based on the argentophilic interaction, one exhibiting a honeycomb layer formed by the fusion of macrocyclic Ag16rings and the other furnishing the first example of a Ag∞tubular motif.(4) On the basis of our previous studies about adjacent dense polycar boxy late ligands, we designed and prepared a new polycarboxylate ligand1,1’-biphenyl-2,2’,6,6’-tetracarboxylic acid (H4bptc), and obtained five silver-organic frameworks (22-26) under solvent evaporation condition in the presence of N-containing auxiliary ligands (bpy=4,4’-bipyridine, bpe=1,2-bis(4-pyridyl)ethene). In complexes {[Ag4(bptc)(bpy)4(H2O)]·(H2O)12}n (22) and {[Agi.5(bptc)o.5(bpy)1.5]·(NH4)0.5·(H20)3}n (23), butterfly shaped16-membered water ring and infinite water tape are obtained, respectively. In complex {[Ag2(H2bptc)(bpy)2]·(H2O)2}n (24), the water molecules reside in the void space of the three-dimensional supramolecular framework. Both compounds {[Ag2(H2bptc)(bpy)2]·(HC1O4)}n (25) and {[Ag(H2bptc)0.5(bpe)](H2O)2}n (26) are2-fold interpenetrated3D frameworks.The investigations in this section not only illustrate that diversity of structural and compositional coordination polymers can be achieved by changing the number of carboxyl groups, the neutral ligands, pH value, but also provide that aromatic multicarboxylic acid ligands are good candidates for construction of silver-organic coordination polymers. These results also provide new ideas for design of functional silver-organic frameworks.