From discrete dinuclear to 1-D and 2-D structures: nickel dipicolinate complexes with flexible bis(imidazole) ligands

Three new complexes, [Ni₂(dpc)₂(L₁)₂(H₂O)₂]?·?4H₂O (1), [Ni(dpc)(L₂)_1.5] _n (2), and {[Ni(dpc)(L₃)_1.5]?·?2H₂O} _n (3), where H₂dpc?=?dipicolinic acid, L₁?=?1,4-bis(2-methylimidazol-1-yl)butane, L₂?=?4,4′-bis(2-methylimidazol-1-ylmethyl)biphenyl, and L₃?=?1,4-bis(benzimidazol-1-yl)-2-butylene, have been synthesized by hydrothermal methods and characterized by elemental analyses, infrared spectra, thermogravimetric analysis, and X-ray crystallography. The common structural characteristic of the three complexes is that the Ni²⁺ is coordinated by tridentate dipicolinate through nitrogen of pyridine and oxygen of carboxylate, serving as a terminal ligand. In 1, two L₁ link two [Ni(dpc)(H₂O)] units to a discrete binuclear metallomacrocycle with a 22-membered ring, which is assembled through multiple O–H?···?O hydrogen bonds to form a 3-D supramolecular framework. Complex 2 exhibits a 1-D ladder-like chain structure constructed by cis/trans-conformation L₂ linking metal centers; 3 displays a 2-D (6,3) topology, being constructed from the linking of [Ni(pdc)] by L₃. These results indicate the merits of flexible bis(imidazole) ligands as building blocks with dipicolinate for the construction of complexes with diverse structural motifs.     

Transition metal coordination complexes based on V-shaped bis-triazole ligand: syntheses,structures, and properties

Hydrothermal reactions of 1,3-bis(1,2,4-triazol-1-yl)benzene (btb) and M(NO₃)₂ (M = Co²⁺ (1), Cu²⁺ (2)) afforded two new coordination polymers, [Co(btb)₂(NO₃)(H₂O)]_n·NO₃·H₂O (1) and [Cu(btb)₂(NO₃)₂]_n (2), respectively. Single-crystal X-ray diffraction reveals that 1 crystallizes in the space group P2₁/m and 2 crystallizes in the space group Pī, both showing a double-stranded chain structure. The 1-D chains are interconnected via π?π interactions to lead to 2-D ladder-like supramolecular architectures. In addition, magnetic behavior and thermal stability of 1 and 2 have been investigated. For 1, weak antiferromagnetic interactions are observed at low temperature, and the data obey the Curie–Weiss law χ_M = C/(T?θ), with C = 3.22 cm³·mol^?1·K and θ = ?10.39 K. For 2, the decrease of the χT vs. T curve at low temperature is the result of intermolecular antiferromagnetic magnetic interactions.     

Self-assembly of 1-D, 2-D,and 3-D transition-metal coordination polymers based on a T-shaped tripodal ligand 4-(4,5-dicarboxy-1H-imidazol-2-yl)pyridine 1-oxide

Three coordination polymers, {[Co(C₁₀H₅N₃O₅)(H₂O)₂]·H₂O}_n (1), {[Mn₃(C₁₀H₅N₃O₅)₂Cl₂(H₂O)₆]·2H₂O}_n (2), and {[Cu₃(C₁₀H₄N₃O₅)₂(H₂O)₃]·4H₂O}_n (3), based on a T-shaped tripodal ligand 4-(4,5-dicarboxy-1H-imidazol-2-yl)pyridine 1-oxide (H₃DCImPyO), were synthesized under hydrothermal conditions. The polymers showed diverse coordination modes, being characterized by elemental analysis, infrared spectroscopy, and single-crystal X-ray structure analysis. In 1, the HDCImPyO^2? generated a 1-D chain by adopting a μ₂-kN, O : kN′, O′ coordination mode to bridge two Co(II) ions in two bis-N,O-chelating modes. In 2, the HDCImPyO^2? adopted a μ₃-kN, O : kO′, O′′ : O′′′ coordination mode to bridge two crystallographically independent Mn(II) ions, forming a 2-D hcb network with {6³} topology. In 3, by adopting μ₄-kN, O : kO′, O′′ : kN′′, O′′′ : O′′′′ coordination, DCImPyO^3? bridged three crystallographically independent Cu(II) ions to form a 3-D framework having the stb topology.     

Two new 2-D coordination polymers based on a purine-containing carboxylate

A purine-containing multifunctional ligand, 2-(6-oxo-6H-purin-1(9H)-yl)acetic acid (HL), and two new 2-D coordination polymers, [Co(L)₂(H₂O)₂] _n?·?2nH₂O (1) and [Ni(L)₂(H₂O)₂] _n?·?2nH₂O (2), were synthesized and characterized. Polymers 1 and 2 have isomorphous structures with (4,4)-connected topologies composed of left- and right-handed metal–organic helices sharing common metal centers. Two helical conformations in the same net are stabilized by strong π–π stacking interactions between purine groups. Through direct and water-mediated interlayer hydrogen-bond interactions those layers are assembled into stable 3-D supermolecules where slight differences in the strength of hydrogen bonds and coordination bonds result in their decomposition behaviors.     

Three 1-D molybdenum(V) phosphates with copper/nickel coordination cations

Three 1-D reduced molybdenum(V) phosphates, [Ni(OH)₂][Na₂(H₂O)₃]₂{Ni[(MoO₂)₆(OH)₃(HPO₄)₃(PO₄)]₂}?·?2C₆H₁₄N₂?·?2H₃O?·?5H₂O (1), [Ni(H₂O)₂][K(H₂O)₅]₂{Ni[(MoO₂)₆(OH)₃(HPO₄)₃(PO₄)]₂}?·?2C₆H₁₄N₂?·?2H₃O?·?4H₂O (2), and [Cu(H₂O)₂][Na(H₂O)₅]₂{Cu[(MoO₂)₆(OH)₃(HPO₄)₃(PO₄)]₂}?·?2C₆H₁₄N₂?·?2H₃O?·?4H₂O (3), have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. The crystallographic analysis reveals that 1 is based on {Ni[Mo₆O₁₂(OH)₃(HPO₄)₃(PO₄)]₂} clusters connected through {[Ni(OH)₂][Na₂(H₂O)₃]₂} pentanuclear mixed-metal cluster units to yield unusual 1-D chains along the c-axis, which further form 3-D supramolecular networks via hydrogen-bonding. Compounds 2 and 3 are heterogeneous isostructural compounds. Both are built from M[Mo₆P₄]₂ (M?=?Ni or Cu) blocks as the structural motif combined with [MO₄(H₂O)₂] (M?=?Ni or Cu) octahedra to form 1-D chains, where M[Mo₆P₄]₂ (M?=?Ni or Cu) is bonded by [M′(H₂O)₅] (M′?=?K or Na). Furthermore, bulk carbon paste electrode modified with 1 (1-CPE) displays good electrocatalytic activity toward reduction of nitrite or bromate.     

Syntheses and structures of Cd(II) and Co(II) compounds of 4-[(3-pyridyl)methylamino]benzoate anion

Three coordination polymers containing Cd(II) and Co(II), connected via 4-[(3-pyridyl)methylamino]benzoate (L^?), have been synthesized in hydrothermal conditions. In [Cd(L)Cl] _n (1), adjacent Cd(II) cations are linked by carboxylates to give a dinuclear cluster. Pairs of L^? bridge the dinuclear cluster to form double helical chains, and these chains are further linked by Cl^? to produce a 4-connected net with (4²?·?6³?·?8) topology. [CdL₂] _n (2) contains 1-D ladder-like chains. The packing structure displays a 3-D supramolecular structure, with π?···?π interactions stabilizing the framework. [CoL₂] _n (3) has a 2-D extended supramolecular structure via π?···?π interactions of 1-D coordination polymers of 3. The crystal structures of 1–3 have been determined by single-crystal X-ray diffraction. Luminescent properties for 1 and 2 are discussed.     

Three cobalt coordination polymers based on bis(1,2,4-triazol-1-ylmethyl)benzene positional isomer ligands and thiocyanate

The reaction of three positional isomer ligands of bis(1,2,4-triazol-1-ylmethyl)benzene and Co(NCS)₂ gives three coordination polymers [Co(obtz)₂(NCS)₂] _n (1), [Co(mbtz)₂(NCS)₂] _n (2), and {[Co(bbtz)₂(NCS)₂]?·?2DMF} _n (3). Polymers 1 and 2 are comprised of similar 1-D double chains. In 1, each chain forms π–π stacking interactions with four adjacent chains (two above and two below) to extend to a 3-D supramolecular network. Polymer 3 is a neutral 2-D (4,4) network. The dangling NCS^? inserts into the window of adjacent layers in a mutual relationship and result in a 2-D?→?3-D polythreaded network in 3. The thermal stability and the diffuse reflectance UV-Vis spectroscopy of 1, 2, and 3 were measured.     

Syntheses,structures, and luminescence of two Zn(II) coordination polymers based on 5-(4-imidazol-1-yl-phenyl)-2H-tetrazole and carboxylates

Reactions of Zn(II) salts, 5-(4-(1H-imidazol-1-yl)phenyl)-1H-tetrazolate (HIPT) and 2-mercaptobenzoic acid or 2-propyl-1H-imidazole-4,5-dicarboxylic acid (H₃PrIDC), result in two mixed-ligand coordination polymers (CPs), [Zn₂(IPT)(DSDB)(OH)]_n (H₂DSDB = 2,2′-disulfanediyldibenzoic acid, 1) and [Zn₂(IPT)(PrIDC)(H₂O)]_n (H₃PrIDC = 2-propyl-1H-imidazole-4,5-dicarboxylic acid, 2). Compound 1 possesses a 2-D structure built by 1-D [Zn(IPT)]_n chains and DSDB^2? connectors, in which the DSDB^2? is generated via in situ reaction from 2-mercaptobenzoic acid. It displays a new intricate 4-nodal {3·4·6·7·8·9}{3·6·7·8·9·10}{3·8·9}{4·6·8} topology. Compound 2 displays a 3-D framework with new 3-connected topology with Schläfli symbol of (4·8·10) (8·12²), in which the 1-D Zn-carboxylate chains were bridged by 3-connected IPT^? ligands. The thermal stabilities and luminescence properties of 1 and 2 have also been studied. The compounds exhibit intense solid-state fluorescent emissions at room temperature.     

Synthesis,structure, cytotoxic activities,and DNA-binding of 1-D copper(II) and zinc(II) coordination polymers

Two 1-D coordination polymers have been synthesized and identified as [Zn(ox)(en)] _n (H₂O)_{2 n} (1) and [Cu₂(dmeo)(N₃)₂] _n (2), where en represents diaminoethane, ox and dmeo stand for dianions of oxalic acid and N,N′-bis[2-(dimethylamino)ethyl]oxamide, respectively. Polymer 1 was characterized by elemental analysis, molar conductance measurement, IR and electronic spectra, and single-crystal X-ray diffraction. Polymer 1 consists of 1-D chains bridged by oxalate. The Zn^II can be described as a distorted octahedral environment and the Zn^II···Zn^II separation through the μ-oxalato-bridge is 5.5420(9)?Å. Hydrogen bonds assemble the coordination polymers to a 3-D supermolecular structure. The crystal structure of 2 has been reported previously. However, the bioactivities were not studied. The DNA-binding properties and cytotoxic activities of the two coordination polymers are investigated. The results suggest that the two polymers interact with HS-DNA in groove binding with binding affinity following the order of 1?>?2, which is consistent with their anticancer activities.     

Two independent, 1-D metal–organic nanotubes based on rings or helical chain units

Three coordination polymers {[Mn(bte)(NO₂-1,3-bdc)(H₂O)]·H₂O}_n (1), {[Mn(btp)(NO₂-1,3-bdc)(H₂O)]·2H₂O}_n (2), and {[Mn(btb)(NO₂-1,3-bdc)(H₂O)]·H₂O}_n (3) (bte, 1,2-bis(1,2,4-triazol-1-yl)ethane; btp, 1,3-bis(1,2,4-triazol-1-yl)propane; btb, 1,4-bis(1,2,4-triazol-1-yl)butane, NO₂-1,3- H₂bdc, 5-nitroisophthalic acid) were synthesized by combination of bte, btp, and btb, conformationally flexible ligands with different spacer lengths, and the rigid [NO₂-1,3-bdc]^2?. In 1, two [NO₂-1,3-bdc]^2? anions link adjacent [Mn₂(bte)₂] rings to give an independent, 1-D metal–organic nanotube (MONT). The structure of 2 is an undulating 2-D (4,4) network. In 3, the combination of a [Mn(btb)]_n single helical chain and two [Mn(NO₂-1,3-bdc)]_n linear chains assemble an intriguing independent, 1-D MONT. An interesting structural feature of 1 and 3 is that the nitro groups of each 1-D MONT interpenetrate into two adjacent 1-D MONTs to form a 1-D → 2-D interdigitated array. 3-D architectures in 1 and 3 are assembled via hydrogen bond interactions. The luminescent properties and thermal stabilities of 1, 2, and 3 were investigated.     

Anion-driven Ag(I) coordination architectures: structural diversity and photoluminescence behaviors

To observe anion impact on structural diversity of coordination architectures, three 1-D Ag(I) complexes with distinct features have been prepared, {[Ag(bpbib)₂(NO₃)]·C₃NH₉O)}_n (1), [Ag₂(bpbib)₂·(BF₄)₂]_n (2), and [Ag₂(bpbib)₂·(ClO₄)₂]_n (3), by the reactions of 4,4′-bis((2-(pyridin-2-yl)-¹H-benzo[d]imidazol-1-yl)methyl)biphenyl (bpbib) with Ag(I) salts. Complex 1 is a 1-D helical chain, whereas 2 and 3 bear ligand-unsupported Ag(I)···Ag(I) interaction-directed 1-D structural motif, with synergetic working of flexible organic linker and anions. All complexes exhibit strong triplet state emission at cryogenic temperatures, which profits from the reduction of nonradiative transitions.     

Hydrothermal synthesis,structure, and properties of lead(II)-based coordination compounds with R-isophthalic acid (R=OH,CH3)

Three new lead(II)-based coordination polymers, [Pb(5-OH-BDC)] _n ?·?nH₂O (1) (5-OH-BDC?=?5-hydroxyisophthalate), [Pb₂(5-CH₃-BDC)₂] _n (2), and [Pb₂(5-CH₃-BDC)₂(phen)₂] _n ?·?2nH₂O (3) (5-CH₃-BDC?=?5-methylisophthalate, phen?=?1,10-phenanthroline), have been hydrothermally synthesized, structurally determined by single-crystal X-ray diffraction, and characterized by elemental analyses, IR spectra, and thermogravimetric analyses. Both 1 and 2 exhibit 2-D double-layer network structures, while 3 possesses 1-D chain structure bridged by 5-CH₃-BDC. The coordination sphere of Pb(II) in 1 is holodirected, whereas in 2 and 3 the spheres feature hemidirected structures. Fluorescence properties of 1–3 have been investigated in the crystalline state at room temperature.     

Synthesis,properties, and X-ray crystal structures of two Ag(I) complexes with 2-(pyridin-4-yl)-1H-imidazole-4,5-dicarboxylic acid

Two 1-D and 3-D Ag(I) complexes involving 2-(pyridin-4-yl)-1H-imidazole-4,5-dicarboxylic acid (H₃PIDC) have been characterized by infrared spectrum, elemental analysis, and single-crystal X-ray diffraction. [Ag₂(HPIDC)]_n (1), synthesized under hydrothermal conditions, gave a 3-D framework; [Ag₂(HPIDC)(MBI)]_n (2) (MBI?=?2-methyl-1H-benzo[d]imidazole), with MBI as the second ligand, gave a 1-D zigzag chain and further formed a 3-D supramolecular structure through π···π interactions. The most interesting structural features of these complexes are the presence of C–H···Ag hydrogen bonding interactions and Ag···C weak interactions between the Ag centers and H₃PIDC. Luminescence indicates that 2 has significantly stronger fluorescent emissions than 1 in the solid state at room temperature.     

Two cadmium(II) addition compounds with 3-hydroxy-2,7-naphthalenedisulfonate containing aromatic diamines and their 3-D net

{[CdCl(2,2′-bipy)₂(H₂O)]⁺·[Cd(3-O^?-2,7-NDS)(2,2′-bipy)₂]^?·3H₂O} (1) and {[Cd(phen)₃]²⁺·2[Cd(3-O^?-2,7-NDS)(phen)₂]^?·8.5H₂O} (2) (3-OH-2,7-NDS?=?3-hydroxy-2,7-naphthalenedisulfonate, phen?=?1,10-phenanthroline, and 2,2′-bipy?=?2,2′-bipydine) were prepared and characterized by X-ray single-crystal diffraction. Compound 1 contains a discrete coordination cation [CdCl(2,2′-bipy)₂(H₂O)]⁺ and a coordination anion [Cd(3-O^?-2,7-NDS)(2,2′-bipy)₂]^?; 2 contains a discrete coordination cation [Cd(phen)₃]²⁺ and two coordination anions [Cd(3-O^?-2,7-NDS)(phen)₂]^?. There are numerous weak interactions among the coordination cation, coordination anion, and free water molecules, such as O–H?···?O hydrogen bonds, π?···?π stacking, and Cl^??···?π interactions in 1 and π?···?π stacking and C–H?···?π interactions in 2. The cations and anions as building blocks are connected to construct different 3-D supramolecular architectures via weak intermolecular interactions. Particularly, the capsule structure of 1 was observed.     

Syntheses,structures, and properties of four coordination compounds constructed from asymmetric semi-rigid V-shaped multicarboxylate ligand

Four new compounds, [Mn(HL)(phen)₂(H₂O)] (1), [Ni(HL)(phen)₂(H₂O)] (2), [Zn(HL)(4,4′-bipy)_1.5(H₂O)] _n ?·?2nH₂O (3) and [Zn₂(HL)₂(H₂O)₆] (4), have been synthesized from an asymmetric semi-rigid V-shaped multicarboxylate 4-(4-carboxy-phenoxy)-phthalic acid (H₃L) with 1,10-phenanthroline (phen), or 4,4′-bipyridine (4,4′-bipy) as auxiliary ligands. Single-crystal X-ray diffraction analysis reveals that 1, 2 and 4 have 0-D structures with 3-D supramolecular frameworks formed by intermolecular hydrogen bonds. Compound 3 shows a 1-D infinite ribbon bridged by 4,4′-bipy, which further forms a 3-D supramolecular architecture by π–π stacking interactions and hydrogen bonds. Thermal stabilities of 1–4 and luminescence properties of 3 and 4 have also been investigated.     

Cd(II) MOFs based on cadmium/carboxylate units and 4,4′-bis(benzoimidazol-1-yl)bibenzene: syntheses,structures, and luminescence

Solvothermal reactions of CdCl₂·2.5H₂O with 4,4′-bis(benzoimidazol-1-yl)bibenzene (bimbb) and 1,4-benzenedicarboxylic acid (1,4-H₂bdc), 4,4′-biphenyldicarboxylic acid (4,4′-H₂bpdb), 5-methyl-1,3-benzenedicarboxylic acid (5-Me-1,3-H₂bdc), or 1,3,5-benzenetricarboxylic acid (H₃btc) afforded four 3-D metal–organic frameworks, {[Cd₂(1,4-bdc)₂(bimbb)₂]·H₂O}_n (1), {[Cd₂(4,4′-bpdb)₂(bimbb)(H₂O)₂]} _n (2), [Cd₂(5-Me-1,3-bdc)₂(bimbb)] _n (3), and {[Cd₃(btc)₂(bimbb)(H₂O)₂]·2H₂O} _n (4). Complexes 1–4 were characterized by elemental analysis, IR spectroscopy, powder X-ray powder diffraction, and single-crystal X-ray diffraction. 1 possesses a 3-D framework with 2-D undulated (8,4) layers which are further connected by bimbb pillars. 2 forms a 3-D pillared-layer framework constructed through 2-D undulated (4,4) layers and bimbb pillars. 3 has 1-D ribbons of [Cd₄(5-Me-1,3-bdc)₄] _n which are linked by bimbb to form a 3-D structure. 4 exhibits a 3-D pillared-bilayer framework consisting of (6,3) double-decker [Cd₉(btc)₆(μ-OH₂)₆] _n layers and bimbb pillars. The Schläfli symbols for the four frameworks are (4²·6³·8)(4²·6⁵·8³) (1), (4⁴·6⁶) (2), (4⁴·6²)(4⁶·6⁴) (3), and (6³)(6¹⁰) (4). The photoluminescent properties of 1–4 were also investigated.     

Two solvent directed zinc(II) coordination polymers with 1-D single-zigzag chain and 1-D double-zigzag chains

Two coordination polymers, {[Zn(NiL)(DMA)(H₂O)₂] (DMA)(H₂O)} _n (1) (DMA?=?N,N-dimethylacetamide) and {[Zn₂(NiL)₂(DMF)(H₂O)₄]?·?3DMF} _n (2) (DMF?=?N,N-dimethylformamide), have been prepared by reactions of Zn(NO₃)₂?·?6H₂O and NiL in CH₂Cl₂-DMA–H₂O and CH₂Cl₂-DMF–H₂O, respectively. H₂L denotes dimethyl 5,6,7,8,15,16-hexahydro-6,7-dioxodibenzo-9,10-benzo-[1,4,8,11]tetraazacyclotetradecine-13,18-dicarboxylate. Single-crystal X-ray diffraction analyses reveal that coordination geometries around Ni(II) are identical with slightly distorted square planar and all Ni–N bonds are very short. Complex 1 shows 1-D zigzag chain structure, while 2 has 1-D double-zigzag chains. The chains, which are packed parallel in 1 and 2, are interconnected by lattice solvent through O–H···O and C–H···O hydrogen bonds to form 3-D supramolecular networks. We discuss solvent effects on assembly of the two coordination polymers. The results reveal that coordinated solvent has influence on the assembly procedure.     

Synthesis,structures, and fluorescence of two cadmium(II) coordination polymers with a semirigid bis-benzimidazole

Compounds [CdLCl₂] _n (1) and {[Cd(L)₂(ClO₄)]·ClO₄} _n (2), where L?=?1,3-bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene, have been synthesized by hydrothermal method, and characterized by element analysis, IR spectra, Powder XRD, and X-ray crystallographic diffraction. Cd(II) in 1 and 2 are both trigonal bipyramidal. Different cadmium salts of chloride and perchlorate lead to different configurations of [Cd₂L₂]²⁺, trans-form in 1 but trans and cis-forms in 2. The 1-D beaded chains of 1 are further linked to generate a 3-D supramolecular architecture by strong π–π stacking interactions as well as intermolecular C–H?···?Cl hydrogen bonds. In 2, the 1-D beaded chains are further assembled by intermolecular C–H?···?O hydrogen bonds to form a 2-D layer. Solid-state fluorescent properties of 1 and 2 were investigated at room temperature.     

Four Zn(II)/Cd(II) coordination polymers derived from isomeric benzenedicarboxylates and 1,6-bis(triazol)hexane ligand: synthesis,crystal structure,and luminescent properties

Four coordination polymers, [Zn(o-bdc)(bth)_0.5(H₂O)] _n (1), [Cd(o-bdc)(bth)_0.5(H₂O)] _n (2), [Zn(m-bdc)(bth)] _n (3), and [Cd(p-bdc)(bth)?·?(H₂O)₂] _n (4) (where o-bdc?=?1,2-benzenedicarboxylate, m-bdc?=?1,3-benzenedicarboxylate, p-bdc?=?1,4-benzenedicarboxylate, and bth?=?1,6-bis(triazol)hexane), have been hydrothermally synthesized and structurally characterized. Both 1 and 2 are isostructural, featuring two binodal architectures: (6³)(6⁵·8) topology in terms of o-bdc and Zn^II/Cd^II as three- and four-connected nodes. Complex 3 shows a 2-D (4,4) network with the Zn?···?Zn?···?Zn angle of 57.84°, whereas 4 exhibits planar 2-D (4,4) network. These 2-D networks of 3 and 4 are extended by supramolecular interactions, such as CH?···?π/π–π stacking and hydrogen-bonding into 3-D architecture. A structural comparison of these complexes demonstrates that the dicarboxylate building blocks with different dispositions of the carboxyl site play a key role in governing the coordination motifs as well as 3-D supramolecular lattices. Solid-state properties such as photoluminescence and thermal stabilities of 1–4 have also been studied.