Synthesis and characterization of homo- and heterometallic metal–organic frameworks based on 1,2,4,5-benzenetetracarboxylate ligand

Two new three-dimensional metal–organic frameworks, [H₂N(CH₃)₂]₂[Zn(btec)]·DMF (1, H₄btec = 1,2,4,5-benzenetetracarboxylate acid) and [H₂N(CH₃)₂][ZnLi(btec)]·DMF (2), have been solvothermally synthesized and structurally characterized by single crystal X-ray diffraction. Compound 1 based on μ₄-btec features an anionic homometallic framework with 4-connected pts topology. Compound 2 is a heterometallic organic framework with rare (4, 4, 8)-connected network topology, which can be considered as constitute of a Li-btec (pts) net and a Zn-btec net. Moreover, the luminescent properties of two compounds are investigated in the solid state at room temperature.     

Polycatenated Bilayer Structure Containing Honeycomb-like 63 Layers

A new luminescent Zn(II) compound, [Zn₂(IN)₃(bpy)_0.5(CH₃COO)]·2(DMA) (1, IN = isonicotinate, bpy = 4,4′-bipyridine, DMA = N,N-dimethylacetamide), was synthesized under solvothermal condition and structurally characterized by single crystal X-ray diffraction. Compound 1 features a (3,4)-connected bilayer structure with honeycomb-like 6³ layers and bpy pillars. Each individual bilayer is catenated with two adjacent bilayers, giving rise to a rare 2D + 2D → 3D polycatenation motif.     

Hydrothermal syntheses and crystal structures of PbII coordination polymers based on a N,O-donor ligand

In this article, four new lead(II) coordination polymers based on a N,O-donor ligand 2′-(1 H-1,3,7,8-tetraaza-cyclopenta[l]phenanthren-2-yl)biphenyl-2-carboxylic acid (HL) have been hydrothermally synthesized, namely, [PbL₂]·2H₂O (1), [PbL₂]·2H₂O·CH₃CH₂OH (2), [Pb₅L₂(m-BDC)₄]·3H₂O (3) and [Pb₂L₂(p-BDC)] (4), where m-BDC = 1,3-benzenedicarboxylate and p-BDC = 1,4-benzenedicarboxylate. Compound 1 shows a 2D bilayer structure, which is further extended into a 3D supramolecular structure through π–π stacking interactions. Compound 2 shows a 3D supramolecular structure based on a zero-dimensional molecule by π–π stacking interactions of neighboring molecules. Compound 3 shows a 2D layer structure. Compound 4 displays a 1D chain-like structure, which is then stacked by π–π interactions to result in a 2D supramolecular structure. Solid-state luminescent spectra of four lead(II) complexes indicate intense fluorescent emissions.     

Synthesis, Crystal Structure and Luminescent Property of a New Two-Dimensional Zn(II) Coordination Polymer Based on Oxalic Acid and 1,4-Bis(imidazol-1-ylmethyl)-benzene

A new Zn(II) coordination polymer based on oxalic acid and 1,4-bis(imidazol-1-ylmethyl)benzene (bix), namely, [Zn(C₂O₄)(bix)]_n (1), has been successfully synthesized under hydrothermal conditions. Its structure has been determined by single crystal X-ray diffraction analysis, elemental analyses and IR spectroscopy. Compound 1 shows a two-dimensional (2D) layer structure. The intermolecular C–H···O interactions extend the compound 1 into 3D supramolecular architectures and play an important role in stabilizing compound 1. In addition, the luminescent property of the compound has also been investigated in solid state at room temperature.     

Cu(II) and Zn(II)-Pyridine-2,3-Dicarboxylate Complexes with 2-Methylimidazole: Syntheses, Crystal Structures, Spectroscopic and Thermal Analyses

Two new Cu(II) and Zn(II)-pyridine-2,3-dicarboxylate (pydc) complexes with 2-methylimidazole (2-Meim), [Cu(pydc)(2-Meim)₃]·H₂O (1) and {[Zn(μ-pydc)(H₂O)(2-Meim)]·H₂O}_n (2) have been synthesized and characterized by elemental, spectral (IR and UV–Vis.) and thermal analyses. The molecular structures of mononuclear (1) and polynuclear (2) complexes have been determined by the single crystal X-ray diffraction. Compound 1 crystallizes in the triclinic P ? 1 space group, while compound 2 crystallizes in the monoclinic P2₁/c space group. The pyridine-2,3-dicarboxylate ligand acts in two different coordination modes; namely, bidentate-(N,O) for 1 and μ-tridentate-(N,O,O) for 2, the latter displaying a 1D polynuclear structure. The crystal packing of the complexes exhibit 3D supramolecular frameworks including channels by C–H···π, π···π, and N–H···O interactions. Water molecules occupy the channels by O–H···O hydrogen bonds.     

A novel 3D Zn(II) coordination polymer for highly luminescent sensing of nitro compounds

A novel 3D coordination polymer [Zn_2.5(L)(trz)₂(H₂O)₂]·2H₂O (1) (H₃L = 5-(4-carboxybenzyloxy)isophthalic acid, trz = 1,2,4-triazole) has been synthesized hydrothermally. Compound 1 displays a 3D (3,8)-connected net with (5³)₂(5⁸·6⁴·7⁸·8⁴·9⁴) topology. The luminescent property of 1 dispersed in different solvents as well as nitro compounds have been investigated systematically, demonstrating high detection sensitivity via a fluorescence quenching mechanism.     

An unprecedented stable self-penetrating metal-organic framework with solvent-dependent luminescence properties

A fascinating 3D pillared-layer structure, namely [Cd₃(bpea)₂(trz)₂(H₂O)₂]·DMF (1), has been isolated under hydrothermal condition by reaction of cadmium salt, biphenylethene-4,4′-dicarboxylic acid (bpea) and 1,2,4-triazole (Htrz). Compound 1 presents an unusual self-penetrating network displaying uninodal seven-connected {4¹⁴·5·6⁶} topology with trinuclear cadmium clusters as seven-connected nodes, which exhibited exceptional resistance to acid/base aqueous solutions. Furthermore, solvent-dependent luminescence properties of 1 were investigated, and the results showed that 1 could serve as a potential luminescent sensor in detecting traces of the target species, such as toluene and nitrobenzene.     

Metal-organic fameworks based on multi-carboxylate ligands with threefold symmetries and luminescence properties

Three new metal–organic frameworks, namely, [Cd_1.5(tcpb)(DMF)(H₂O)] (1), [Co_1.5(tcpb)(DMF)₂]·3DMF (2) and [Zn(Htcpb)(4,4′-bpy)_0.5]·1.5H₂O (3) (tcpb = 1.3,5-tris(4-carbonylphenyloxy)benzene) have been synthesized by solvent-thermal method. The single-crystal X-ray diffraction analysis shows that compound 1 is 2D grid layers, with the trinuclear cadmium clusters acting as secondary building units (SBUs), and the tcpb ligand serveing as organic linkers. Compound 1 and Compound 2 are isomorphic structures containning similar connection modes of tcpb ligands with trinuclear metal clusters. Compound 3 is a 3D interpenetrated framework based on dinuclear Zn cluster with dia topology. The fluorescence properties for solid state compound 1 and 3 were examined at room temperature. Compared with free tcpb ligands, both of them display remarkable red-shift.     

Hydrothermal Syntheses and Crystal Structures of Three Zn(II) Coordination Compounds Constructed with 3,5-Pyrazoledicarboxylic Acid

Three novel metal–organic coordination compounds, [Zn(Hdcp)(H₂O)₄]·1.5H₂O (1), [Zn(Hdcp)(H₂O)₂]_∞ (2) and [Zn₃(dcp)₂(H₂O)₅]_∞ (3) with the ligand 3,5-pyrazoledicarboxylic acid were prepared by the hydrothermal method. The complexes were structurally characterized by elemental analysis, IR spectroscopy and X-ray single-crystal diffraction. Compound 1 is a mononuclear molecule that is linked into a 3D supramolecular framework via N–H···O and O–H···O hydrogen bonds. In 2, two types of carboxylic bridges were found between Zn^II ions to form a 1D double-chain. The 1D chains were further construct into a 3D structure by hydrogen bonds. Trinuclear 3 consists of 1D bi-infinite parallelogram chains of [Zn₃(dcp)₂(H₂O)₃] trimers. In the basic trinuclear unit a further bridging mode of the ligand is seen where two dcp^3? ligands chelate three Zn^II ions by utilizing five donors of the dcp^3? ligand. The photoluminescent properties of 1, 2 and 3 were investigated.     

Synthesis,structure and photoluminescent properties for sensing nitro explosives of two new Zn(II) coordination polymers based on mixed tetrazolate and carboxylate ligands

Two novel Zn-based coordination polymer through employing of in-situ solvothermal techniques by using NO₂-bdc (2-nitroterephthalic acid), HL₁ = 1-(tetrazo-5-yl)-4-(triazo-1-yl)benzene, HL₂ = 1-(tetrazo-5-yl)-4-(triazo-1-yl)benzene and Zn(NO₃)₂·6H₂O to form [Zn₂(HL₁)₂(NO₂-bdc)]·0.5 (DMA)·CH₃OH·H₂O (1) and [Zn₂(μ₃-OH) (HL₂)·(NO₂-bdc)]·0.5 (DMA)·H₂O (2). The structures have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. In Compound 1, each Zn ion bridges one NO₂-bdc and two HL₁ ligands to yield infinite 2D layers, furthermore the aromatic π –π interactions link the adjacent layers yielding a 3D supramolecular structure. In compound 2, the HL₂ ligands link Zn ions to form a 2D Zn(HL) sheet firstly, and further connected by double NO₂-bdc pillars resulting in bi-pillared-layer type 3D frameworks. Moreover, 1 and 2 are luminescent with blue emission (λ_em = 440 nm and λ_em = 417 nm) in the solid-state. The fluorescent nature of 1and 2 inspired us to explore its potential application as a sensor for the detection of nitro explosives. The result reveals that 1 and 2 could be applied as a fluorescence sensor for NB (nitrobenzene) and 1,3-DNB (1,3-dinitrobenzene) with sensitivity and selectivity.     

Two highly connected frameworks and one polythreading architecture based on multidentate N-donor ligands: Syntheses,structures, characterizations and photoluminescent properties

Three coordination polymers based on multidentate N-donor ligands and polycarboxylate anions, namely, [Co₃(4,4′-tmbpt)₄(btc)₂]·9.5H₂O (1), [Ag₄(4,4′-tmbpt)(btec)(H₂O)₂]·H₂O (2) and [Zn(4,4′-tmbpt)(btec)_0.5(H₂O)]·0.5H₂O (3) (4,4′-tmbpt = 1-((1H-1,2,4-triazol-1-yl)methyl)-3,5-bis(4-pyridyl)-1,2,4-triazole, H₃btc = 1,3,5-benzenetricarboxylic acid, and H₄btec = 1,2,4,5-benzenetetracarboxylic acid) have been prepared under hydrothermal condition. Compound 1 displays a 3D (3,6,8)-connected framework with (4·6²)(4⁴·6¹⁰·8)(4¹⁴·6¹²·8²) topology. Compound 2 is a 3D (4,5,8)-connected framework with (4³·6²·8)(4³·6⁵·8²)(4⁸·6²)(4¹⁰·6¹⁰·8⁸) topology. Compound 3 exhibits a 2D → 3D polythreading architecture. The photoluminescent spectra indicate that at room temperature, compounds 2 and 3 emit green and blue luminescence, respectively.     

Syntheses,Crystal Structures and Physical Properties of Four Zinc/Cadmium Coordination Polymers Based on 4-Nitrophthalic Acid and N-donor Auxiliary Ligands

Four new d¹⁰ metal coordination polymers, [Zn(4-NPA)(2,2-bipy)] _n (1), [Zn(4-NPA)(1,3-bimb)·H₂O] _n (2), [Cd(4-NPA)(2,2-bipy)] _n (3) and [Cd(4-NPA)(1,3-bimb)·H₂O] _n (4) (4-NPAH₂ = 4-nitrophthalic acid, 2,2-bipy = 2,2-bipyridine, 1,3-bimb = 1,3-bis(imidazol-1-ylmethyl)-benzene), have been hydrothermally synthesized and characterized by elemental analyses, IR spectra, and X-ray single crystal diffractions. Compounds 1?3 possess different one-dimensional (1D) chain structures. Compound 4 shows a two-dimensional (2D) layered structure. Moreover, the luminescent and thermal stabilities properties of compounds 1–4 were investigated in the solid state.     

Structures and photoluminescence of coordination polymers assembled from bifunctional ligand containing both tetrazole and imidazole groups

Three new coordination polymers, namely, {[Cu₂(IPT)(SO₄)(OH)(H₂O)]·H₂O}_n (HIPT = 5-(4-(1H-imidazol-1-yl)phenyl)- 1H-tetrazolate, 1), {[Cd₂(IPT)(NPA)(OH)]·H₂O}_n (H₂NPA = 5-nitroisophthalic acid, 2), and {[Zn₂(IPT)(IDC)(H₂O)]·3H₂O}_n (H₃IDC = 1H-imidazole-4,5-dicarboxylic acid, 3), were assembled from a bifunctional organic ligand containing both tetrazole and imidazole groups with/without the aid of carboxylate coligands. Compound 1 possesses 2D structure built by 1D [Cu₂(IPT)(SO₄)(OH)]_n secondary building blocks and IPT⁻ linkers. The 2D networks are linked into 3D supramolecular framework via water chains in helical conformation. Compound 2 displays 3D pillar-layer framework with 2D layers based on tetranuclear Cd(II) SBUs and NPA^2 − pillars. Compound 3 exhibits a 3D framework constructed from the interconnection of 1D [Zn-IDC]_n chains and binuclear Zn₂(IPT)₂ rings. The thermal stabilities of porous compound 3 and luminescent properties of compounds 2 and 3 have also been studied in detail. They exhibit intense solid-state fluorescent emissions at room temperature.     

Hydrothermal Syntheses and Photoluminescent Properties of Two Zinc(II) Coordination Polymers Based on 4,6-di(1<Emphasis Type="Italic">H</Emphasis>-imidazol-1-yl)-1,3,5-triazin-2-ol

Two new Zn(II) coordination polymers based on the tridentate ligand 4,6-di(1H-imidazol-1-yl)-1,3,5-triazin-2-ol (Hdit), namely, {[Zn(dit)₂(H₂O)₂]·4H₂O}_n (1) and [Zn(dit)(CH₃COO)]_n (2), have been successfully constructed by varying the metal salts. Compound 1 shows 1D zigzag chain structure, and compound 2 is a 3D binodal (3,5)-connected architecture with {4²·6⁶·8²}{4²·6} topology. The photoluminescent spectra indicate that at room temperature, compounds 1 and 2 emit violet and blue luminescence, respectively.     

First zinc complex of an amino acid pyrazole conjugate: synthesis and crystal structure of {Zn[3-(Ac-Phe)-5-methyl-pyrazole]2}2(ClO4)4

The zinc(II) complex, of the dimeric {Zn[3-(Ac-Phe)-5-methyl-pyrazole]₂}₂(ClO₄)₄ (5) was obtained by the reaction of the amino acid–pyrazole conjugate, 3-(Ac-Phe)-5-methyl-pyrazole (4) and Zn(ClO₄)₂. An acetone solvate of this complex was analyzed by single crystal X-ray crystallography, which establishes the dimeric nature of the complex with a large Zn–Zn separation of 5.551(6) Å and exbihiting coordination to the distorted trigonal bipyramidal zinc centers through the amino acid CO and the pyrazole N.     

Three new coordination polymers based on 4-oxo-1(4H)quinolineacetate: Synthesis,structures and luminescent properties

Reactions of 4-oxo-1(4H)-quinolineacetic acid (Hoqa) and varied metal salts of Zn(II), Cd(II) and Ag(I) resulted in the formation of three new coordination polymers, namely, [Zn(oqa)₂]·H₂O (1), [Cd(bpy)(oqa)₂(H₂O)₂]·4H₂O (2) and [Ag(bpy)(oqa)]·2H₂O (3) (bpy = 4,4′-bipyridine). Complex 1 has a three-dimensional (3D) polymeric network with diamondoid topology; compounds 2–3 exhibit one-dimensional (1D) chain structure characteristics, which are further assembled through π–π stacking attractions and hydrogen bonds, forming the 3D supramolecular frameworks. In addition, the solid-state luminescent properties of the ligand Hoqa and complexes 1–2 have been investigated at room temperature.     

Synthesis,structure and luminescent property of a new Zn(II) coordination polymer with isolated tetrahedral {Zn4O} clusters as building subunits

A new luminescent Zn(II) coordination polymer, namely [Zn₄(L)₂(μ₄-O)(H₂O)₂(DMF)]_n (1 H₃L = biphenyl-3,4,5-tricarboxylic acid, DMF = N,N′-dimethyl formamide) has been synthesized by combining the H₃L ligand with Zn(II) salts under solvothermal conditions. Single-crystal X-ray diffraction analysis reveals that 1 features μ₄-oxygen-bridged tetrahedral {Zn₄O} clusters as building subunits, which are further bridged by L^3 − ligands into a complicated three-dimensional (3D) architecture. Topological analysis reveals that it can be reduced into a (3, 6)-connected topological network with the schläfli symbol of {4 · 6²}₂{4² · 6⁹ · 8⁴}. In addition, the luminescent property of 1 was also investigated in the solid state at room temperature.     

Four New Metal–Organic Supramolecular Networks Based on Aromatic Acid and Flexible Bis(imidazole) Ligand: Synthesis,Structures and Luminescent Properties

Four new metal–organic supramolecular networks, namely, [Zn(H₂pdc)₂(H₂O)₂]·2H₂O·bbi (1), {[Cd(Hpdc)₂]·2H₂O₂·H₂bbi}_n (2), [Zn(BA)₂(bbi)]_n (3), and {[Cd(BA)₂(bbi)]·H₂O}_n (4) (H₃pdc = 3,5-pyrazoledicarboxylic acid, HBA = 3-hydroxybenzoic acid and bbi = 1,1′-(1,4-butanediyl)bis(imidazole)) have been synthesized under hydrothermal conditions and characterized by IR spectra, elemental analyses, and single-crystal X-ray diffraction analyses. Compound 1 possesses zero-dimensional (0D) structure, which is finally extended into a two-dimensional (2D) supramolecular network via O–H···O and C–H···O hydrogen bonds. Complex 2 displays a 2D network structure built from Cd²⁺ atoms interconnected by Hpdc^2? ligands. The adjacent networks are further assembled into three-dimensional (3D) supramolecular structure through O–H···O hydrogen bonds. Compounds 3 and 4 show similar one-dimensional (1D) chains, in which four-coordinated Zn(II) atoms and six-coordinated Cd(II) atoms are bridged by bbi ligands. Through O–H···O and C-H···O hydrogen bonding interactions, the 1D chains are further packed into 2D and 3D supramolecular frameworks for 3 and 4, respectively. Obviously, the structural differences among compelxes 1–4 are attributed to the different central metal atoms and organic ligands. In addition, compounds 1–4 exhibit blue fluorescent emission in the solid state at room temperature.     

Hydrothermal Syntheses,Crystal Structure and Luminescent Properties of Two New Zn(II) Coordination Polymers

Two new zinc(II) coordination polymers; namely, [Zn(BDC)(L)_0.5]_n (1) and {[Zn(BDC)(L)]·3H₂O}(2), were successfully synthesized by the assembly of Zn(II) ion, 1.2-benzene-dicarboxylate acid (H₂BDC) and 1,4-bis(2-methylimidazole-3-ium-1-yl) biphenyl (L). A change in the pH values resulted in complexes with different compositions and dimensionalities. Formed at the lower pH, 1 exhibits a three-dimensional structure with mab topology. At a higher pH, 2 shows a two-dimensional structure, which contains one-dimensional helical chains. The luminescent properties for 1 and 2 were investigated in the solid state at room temperature.     

A photoluminescent 3D silver(I) polymer with mixed 2-naphthol-5-carboxylate and hexamethylenetetramine ligands,showing an unusual (3,4)-connected (6·7·8)2(4·6·7)2(4·7·8)2(72·8)2(62·7·83)(62·72·8·10) topology

The reaction of AgClO₄ with 2-naphthol-5-carboxylic acid (HL) and hexamethylenetetramine (hmt) in the presence of 2,6-dimethylpyridine afforded a photoluminescent three-dimensional (3D) Ag^I polymer {[Ag₆(L)(μ₃-hmt)₂(μ₄-hmt)₂(ClO₄)](ClO₄)₄(H₂O)}_∞ (1), which exhibited an unusual (3,4)-connected (6·7·8)₂(4·6·7)₂(4·7·8)₂(7²·8)₂(6²·7·8³)(6²·7²·8·10) topological network (L = 2-naphthol-5-carboxylate). Moreover, the luminescent properties of 1 have been briefly investigated.