Metal-organic Networks Research Articles

Deliberate design of an acentric diamondoid metal-organic network

Reaction of 2.5-dicarboxy-1-methylpyridinium (DCMP) chloride and Zn(NO 3) 2·6H 2O in the presence of NaHCO 3 in water gave an expected acentric diamondoid network [Zn(DCMP) 2] with a three-fold interpenetration. With long Zn–Zn separations, very large cavities are formed within each diamondoid network with high propensity to interpenetration, which makes it show a promising non-linear optical property with SHG efficiency approximately 7 times higher than that of potassium dihydrogen phosphate (KDP). The design strategy of ligand through methylation of the corresponding pyrdinecarboxylic acid can be extended to other widely used carboxylic acids, more importantly, to lead to an unsymmetric bifunctional bridging ligand, which is essential for generating polar solids.

Synthesis, crystal structure and luminescent properties of one 3D Cd(II) coordination polymer [Cd(H 3BPTC) 2(bpy)] n (H 4BPTC = 1,1′-biphenyl-2,2′,6,6′-tetracarboxylic acid, bpy = 4,4′-bipyridine)

A new 3D metal–organic coordination polymer [Cd(H 3BPTC) 2(bpy)] n ( 1) (H 4BPTC = 1,1′-biphenyl-2,2′,6,6′-tetracarboxylic acid, bpy = 4,4′-bipyridine) has been synthesized and characterized by single X-ray diffraction and IR spectroscopy. The one-dimensional metal–organic chains of the title complex, namely [Cd(H 3BPTC) 2] n , are held together through hydrogen bonding and bridging “second” ligand 4,4′-bpy to give a three-dimensional metal–organic network. The thermal stability of complex 1 was studied by thermal gravimetric (TG) and differential thermal analysis (DTA). Compound 1 exhibits photoluminescence with an emission maximum at ca. 380 nm upon excitation at ca. 251 nm.

Copper(I) Thiocyanate-Amine Networks: Synthesis, Structure, and Luminescence Behavior.

A series of metal-organic networks of CuSCN were prepared by direct reactions with substituted pyridine and aliphatic amine ligands, L. Thiocyanate bridging is seen in all but 1 of 11 new X-ray structures. Structures are reported for (CuSCN)L sheets (L = 3-chloro- and 3-bromopyridine, N-methylmorpholine), ladders (L = 2-ethylpyridine, N-methylpiperidine), and chains (L = 2,4,6-collidine). X-ray structures of (CuSCN)L(2) are chains (L = 4-ethyl- and 4-t-butylpyridine, piperidine, and morpholine). A unique N-thiocyanato monomer structure, (CuSCN)(3-ethylpyridine)(3), is also reported. In most cases, amine ligands are thermally released at temperatures <100 °C. Strong yellow-to-green luminescence at ambient temperature is observed for the substituted pyridine complexes. High solid state quantum efficiencies are seen for many of the CuSCN-L complexes. Microsecond phosphorescence lifetimes seen for CuSCN-L are in direct contrast to the nanosecond-lifetime emission of CuSCN. MLCT associated with pyridine π* orbitals is proposed as the excitation mechanism.

Tunable Quantum Dot Arrays Formed from Self-Assembled Metal-Organic Networks

The confinement of Ag(111) surface-state electrons by self-assembled, nanoporous metal-organic networks is studied using low-temperature scanning tunneling microscopy and spectroscopy as well as electronic structure calculations. The honeycomb networks of Co metal centers and dicarbonitrile-oligophenyl linkers induce surface resonance states confined in the cavities with a tunable energy level alignment. We find that electron scattering is repulsive on the molecules and weakly attractive on Co. The tailored networks represent periodic arrays of uniform and coupled quantum dots.

Losing control? “Design” of crystalline organic and metal–organic networks using conformationally flexible building blocks

Controlling the manner in which organic compounds and metal–organic frameworks assemble in the solid state is an attractive strategy for construction of new functional materials. Most crystal engineering studies employ geometrically well-defined and rigid molecular building blocks in order to limit modes of intermolecular association to only a few (ideally predictable) pathways. Although sacrificing a measure of control, the use of conformationally flexible molecules may provide unique opportunities to construct novel crystalline architectures exhibiting desirable attributes, such as dynamic solid state properties. In this Highlight some of the potential advantages and disadvantages encountered when using flexible components in crystal engineering are discussed. Purely organic systems as well as metal–organic constructs derived from conformationally mobile precursors are described in an effort to demonstrate the impact of molecular flexibility on solid state structure in a range of applications.

Unusual shift of a nitro group in a phenylhydrazo-β-diketone

A novel para to meta shift of a nitro group at the phenyl ring of 3-(2-hydroxy-4-nitrophenylhydrazo)pentane-2,4-dione (H(2)L(1), 1), with formation of the new 3-(2-hydroxy-3,5-dinitrophenylhydrazo)pentane-2,4-dione (H(2)L(2), 2), occurs upon nitration of 1 with an equimolar amount of NaNO(2), under basic conditions. 2 acts as a polydentate ligand for the synthesis of the polymeric potassium [K(μ(5)-HL(2))](n) (3) and monomeric nickel(II) [Ni(H(2)O)(3)(L(2))]·H(2)O (4) compounds. They have been fully characterized, including single crystal X-ray analysis, and the complexes feature metal-organic (in 3) or supramolecular (in 4) 3D networks. The topological analysis of 3 reveals a uninodal 5-connected underlying net with the point symbol of (4(6).6(4)) and a very rare 5/4/t5 topology, which had not yet been observed in coordination polymers.

Copper(ii) metal–organic networks derived from bis(pyridylformyl)piperazineligands and aromatic polycarboxylates: 2D layered structures and a novel 3,5-connected binodal 3D topology

Three novel coordination polymers [Cu2(3-bpfp)(BDC)2(H2O)2]·4H2O (1), [Cu(3-bpfp)(HBTC)]·0.5H2O (2) and [Cu(4-bpfp)0.5(HBTC)(H2O)] (3) have been hydrothermally synthesized by self-assembly of aromatic polycarboxylate ligands H2BDC (H2BDC = 1,3-benzenedicarboxylate acid) or H3BTC (H3BTC = 1,3,5-benzenetricarboxylate acid), bridging ligands 3-bpfp/or 4-bpfp [3-bpfp = bis(3-pyridylformyl)piperazine, 4-bpfp = bis(4-pyridylformyl)piperazine], and copper chloride. X-Ray diffraction analysis reveals that each CuII ion is connected by BDC/or HBTC and 3-bpfp/or 4-bpfp ligands to form two dimensional (2D) layer structures in compounds 1 and 3. Ligands 3-bpfp and 4-bpfp both display μ4-bridging coordination mode in 1 and 3 (via ligation of pyridyl nitrogen and carbonyl oxygen atoms). In compound 2, each CuII ion is connected by HBTC to construct 2D polymeric layers, which are further linked into a novel 3,5-connected 3D coordination polymeric framework with (4·62)(4·66·83) topology by 3-bpfp ligand in μ2-bridging mode (via ligation of pyridyl nitrogen atoms). Compound 2 is the first 3D example of coordination polymer constructed from 3-bpfp and aromatic polycarboxylate ligands. Moreover, the electrochemical properties of the three copper compounds bulk modified carbon paste electrodes have been studied.

Network diversity and supramolecular isomerism in copper(II)/1,2-bis(4-pyridyl)ethane coordination polymers

Reactions of copper(II) sources with 1,2-bis(4-pyridyl)ethane (bpe) yielded metal–organic networks with diverse topologies and dimensionalities. Compounds [Cu(bpe) 2(dmf) 2] n (ClO 4) 2 n ·2 ndmf ( 1·2 ndmf), [Cu(bpe) 2(dmf) 2] n (ClO 4) 2 n ·3.5 ndmf ( 2·3.5 ndmf), [Cu(bpe) 2(NO 3) 2] n ·2 nH 2O ( 4·2 nH 2O) and [Cu 2(bpe)(O 2CMe) 4] n ·0.7 nH 2O ( 5·0.7 nH 2O) have been isolated by altering the copper(II) source, the reaction solvent and the crystallization process. Compounds 1·2 ndmf and 2·3.5 ndmf consist of cationic [Cu(bpe) 2(dmf) 2] 2+ repeating units assembled to 1D and 2D (4,4) networks, respectively, and represent supramolecular isomers due to the conformational isomerism of the bridging bpe molecules. Compound 4·2 nH 2O consists of neutral mononuclear [Cu(dpe) 2(NO 3) 2] repeating units assembled to inclined interpenetrating (4,4) sheets describing an overall entanglement that is 3D in nature, and compound 5·0.7 nH 2O consists of neutral dinuclear repeating units assembled to cross-linked 1D chains.

Recent advances in CdII coordination polymers: Structural aspects, adaptable assemblies, and potential applications

In the past few years, CdII coordination polymers have received much attention due to their diverse structures and interesting properties. This mini-review presents a short summary of the structural styles for such metal-organic networks based on their extended dimensions. Moreover, the influence factors on assemblies and some potential applications will also be commented.

New photoluminescent coordination polymers constructed from dicarboxylate and 1,2-bis(imidazol-1-ylmethyl)benzene

Two new metal-organic frameworks, namely, Cd(Pda)(Bix)0.5(H2O) (I) and Cd2(Glut)2(Bix)(H2O) (II) (H2Pda is 1,3-phenylenediacetic acid, H2Glut is glutaric acid, and Bix is 1,4-bis(imidazol-1-ylmethyl)benzene), have been synthesized under hydrothermal conditions by employing mixed ligands with Cd(II) nitrate. In complex I, the adjacent Cd(II) atoms are bridged by two Pda ligands to result in 1D Cd(II)-Pda double chains, which are further linked by Bix ligands to generate a SQL with the node defined by a Cd(II) dimer, whereas II represents a three-dimensional coordination polymer with an unprecedented (42.5)2(44.59.68.75.82) topology, in which infinite cadmium-carboxylate chains are linked by the ligands to form a metal-organic coordination network. Moreover, the luminescence properties of two complexes have also been investigated.

From a Dissymmetrical Oxamidate Ligand to a 2D Coordination Polymer: Synthesis, Crystal Structure and Magnetic Properties

A new dissymmetrical oxamidate ligand has been used to construct a metal-organic network. Using this ligand, a novel coordination polymer, namely {[Cu(obea)]2Cu・CH3OH・H2O}n (1) [H3obea = N1-(2-carboxyphenyl)-N2-(2-hydroxyethyl)oxalamide] has been synthesized and characterized by single-crystal X-ray analysis. The structure of complex 1 consists of neutral trinuclear complex units. Through syn-anti carboxylate bridges, the complex features a 2D structure with a helical substructure. Its magnetic properties have been investigated.

Stepwise Assembly of Coordination-Based Metal−Organic Networks

Metal-organic networks (MONs) were created by a stepwise solution deposition approach from vinylpyridine-based building blocks and PdCl(2). The combined experimental and computational study demonstrates the formation of saturated, structurally organized systems on solid supports. The rigid nature and geometry of the components are well-suited to form honeycomb and parallelogram structures, as predicted by a computational study. Detailed structural information of the new MONs was obtained by optical (UV/vis) spectroscopy, ellipsometry, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and synchrotron X-ray reflectivity (XRR). Notably, the XPS elemental composition indicates the formation of a palladium coordination-based network.

Hydrothermal syntheses, structures, and properties of four metal–organic coordination polymers assembled from V-shaped tetracarboxylate ligands and N-donor ancillary ligands

A series of four metal–organic frameworks, namely, [Cu(sdpa) 0.5(2,2′-bpy)]·H 2O ( 1), [Zn 2(sdpa)(2,2′-bpy) 2(H 2O) 2]·3H 2O ( 2), [Zn 2(sdpa)(4,4′-bpy)]·3H 2O ( 3), [Cd 2(sdpa)(4,4′-bpy) 1.5(H 2O) 2]( 4), have been hydro(solvo)thermally synthesized through the reaction of 2,3,2′,3′-sulfonyldiphthalic acid (H 4sdpa) with divalent copper, zinc and cadmium salts in the presence of ancillary nitrogen ligands (4,4′-bpy = 4,4′-bipyridine, 2,2′-bpy = 2,2′-bipyridine) and structurally characterized by elemental analysis, IR and X-ray diffraction. Both complex 1 and 2 show metal–organic chain structure, and the adjacent chains are further linked by π⋯π and C–H⋯π interactions for 1 and hydrogen bonds and π⋯π interactions for 2 to form 3D supramolecular structure. In complex 3, two Zn1 and two Zn2 atoms appear alternately and are bridged by sdpa 4− anion ligands to form an infinite Zn-sdpa chain. Such chains are further linked together through 4,4′-bpy ligands in four orientations to form a robust 3D metal–organic network. In compound 4, a 3D Cd-sdpa metal–organic network is accomplished through sdpa 4− anion ligands, and further stabilized by 4,4′-bpy in six orientations. Their luminescence and thermal analysis have also been investigated.

Structural and Chemical Control in Assembly of Multicomponent Metal−Organic Coordination Networks on a Surface

Surface-supported supramolecular self-assembly has been used to generate multicomponent two-dimensional metal-organic coordination networks on a Au(111) surface. The networks consist of linker ligands of 4',4''''-(1,4-phenylene)bis(2,2':6',2''-terpyridine) and nodal ligands of 5,10,15,20-tetra(4-pyridyl)porphyrin that are connected by pyridine-Fe-terpyridine motifs. Scanning tunneling microscopy revealed the coexistence of two polymorphic types of network structures (rhombus and Kagome). Through control of the dosage of the constituent ligands, homogeneous structural phases were obtained selectively. In particular, the rhombus structure could be converted into the more complex and more open Kagome structure by inclusion of guest molecules. Finally, coordination networks providing structural and chemical homogeneity were realized by judiciously choosing the dosages of the constituent ligands and the chemical substitution of the porphyrin ligands.

Structural Investigation of Metal-Organic Cu(II) Coordination Frameworks Constructed from N-donor and α, ω-Dicarboxylate Ligands by One Pot Synthesis: Zigzag Strands, Layered Networks and Its Interaction with Lattice Water Molecules

AbstractTwo metal organic frameworks involving α, ω-dicarboxylates and 2,2′-bpy, [Cu(2,2Bpy)(μ-adipate-H2)] n ·2·H 2 O 1 and [Cu 2 (2,2′-bpy) 2 (μ-adipate-H) 2 (μ-adipate-H2)]·3H 2 O 2 have been synthesized by one pot reaction and structurally characterized. Pentacoordinated Cu(II) zigzag polymeric chain of 1 is composed of linking the adjacent Cu(2,2′-bpy)(H 2 O) units through terminal craboxylate oxygens of two different adipate dianion in cis coordination pattern with the metal center. Both the Complexes were crystallized in triclinic system, P-1 space group with cell parameters a = 6.8948(5), b = 10.7098(7), c = 12.4332(8) A; α = 82.1120(10), β = 80.4950(10), γ = 72.9560(10)°, V = 861.87(10) A 3 for 1, a = 9.5058(6), b = 9.9341(7), c = 12.6460(8) A; α = 70.5080(10), β = 73.5740(10), γ = 75.0720(10)°, V = 1062.05(12) A 3 for 2 respectively. Extensive hydrogen bonding interaction is observed between the lattice water molecules and the coordination network. Compound 2 is a layered architecture, where the neutral framework is constructed by two different adipate anions (in monoanionic and dianionic form) coordinating to the metal center. Interestingly, three water molecules present in the lattice of compound 2 are involved in hydrogen bonding network among themselves, creating a centro-symmetric hexameric water cluster composed of a tetracyclic ring with dangling water molecules attached at alternate positions of the rectangle, which interact with the carboxylate oxygen, thereby extending the hydrogen bonded water network.Graphical AbstractTwo ternary Cu(II) metal-organic coordination networks involving N-donor ligand and adipic acid have been synthesized by one pot reaction. Single crystal investigation revealed that 1 is a zigzag and 2 is a layered network with Cu(II) possessing a distorted square pyramidal geometry. In both the complexes, intricate hydrogen bonding interaction exists between the lattice water molecules with the coordination framework. However, in complex 2, a new topology of hexameric water cluster residing between the adjacent layers of the coordination polymeric network involving hydrogen bonding interactions with the carboxylate oxygens has been observed.[IMAGE]

Supramolecular coordination assemblies constructed from multifunctional azole-containing carboxylic acids.

This paper provides a brief review of recent progress in the field of metal coordination polymers assembled from azole-containing carboxylic acids and gives a diagrammatic summary of the diversity of topological structures in the resulting infinite metal-organic coordination networks (MOCNs). Azole-containing carboxylic acids are a favorable kind of multifunctional ligand to construct various metal complexes with isolated complexes and one, two and three dimensional structures, whose isolated complexes are not the focus of this review. An insight into the topology patterns of the infinite coordination polymers is provided. Analyzed topologies are compared with documented topologies and catalogued by the nature of nodes and connectivity pattern. New topologies which are not available from current topology databases are described and demonstrated graphically.

Analysis on the exchange interactions in three metal-organic coordination network systems possessing one-dimensional magnetism

The nature of the exchange interactions in three metal-organic coordination networks families is examined. These families have a general form ML2(bpy). Since (bpy) molecules are very long, our networks are reduced to effectively one-dimensional chain systems with very weak interchain interaction. The Bonner–Fisher and Fisher classical spin models are applied to fit the magnetic susceptibility data, and results of the fits are discussed. Metal ions inside MCl2(bpy) and M(N3)2(bpy) interact with ferromagnetic interactions and can be described with Fisher classical spin model, while metal ions in M(ox)(bpy) interact with antiferromagnetic interaction and it can be described with the Bonner–Fisher model. Fitting parameter J produced from our models has higher value in M(N3)2(bpy) than in MCl2(bpy) for the same M. It was found that the total spin value is dominant factor to the strength of the magnetic interaction.

A 3-D lanthanum-organic framework containing double chains: La2[NC5H3(CO2)2]3·3H2O

Abstract A three-dimensional La(III) based metal-organic framework, La2[NC5H3(CO2)2]3·3H2O, was assembled using the aromatic linker 3,5-pyridinedicarboxylate. This new compound was synthesized hydrothermally and is an unusual example of a lanthanum containing metal-organic network. The compound contains two distinct La centers, each adopting a nine-coordinate geometry. The structure is built up from zig-zag chains that link via bridging water molecules into a double chain defining edge-sharing six rings. These double chains are arranged into layers and connect through 3,5-pyridinedicarboxylate ligands to give the extended 3-D coordination framework. The material is thermally stable to ca. 360 °C and transforms to an unknown compound before finally decomposing to phase-pure La2O3 at 800 °C. The synthesis, structure, morphology and properties of the new material are described.

Hierarchical Assembly of Extended Coordination Networks Constructed by Novel Metallacalix[4]arenes Building Blocks

Five interesting metal-organic nanostructures and networks, [Ni(4)(HL)(4)(bpy)(py)(H(2)O)(5)](2) x 0.5 H(2)O (1), [Co(4)(HL)(4)(bpy)(py)(H(2)O)(5)](2) x 0.5 H(2)O (2), [Ni(4)(HL)(4)(H(2)O)(7)](n) x nH(2)O (3), [Ni(4)(HL)(4)(bpy)(2)(H(2)O)(4)](n) (4), and [Cd(4)(HL)(4)(H(2)O)](n) (5), were synthesized hydrothermally [H(3)L = 2-(pyridin-2-yl)-1H-imidazole-4,5-dicarboxylate acid, py = pyridine, and bpy = 4,4'-bipyridine]. Intriguingly, all compounds consist of novel metallacalix[4]arene building blocks M(4)(HL)(4), where doubly deprotonated HL in the same bichelating fashion of mu-kN,N':kO,N'' displays a strong coordination orientation by cooperation of the 4,5-imidazoledicarboxylate and 2-pyridyl groups. Very interestingly, the symmetry of M(4)(HL)(4) and the linkage styles between metal nodes and HL in M(4)(HL)(4) are sensitive to the reaction conditions, and the resulting structural motifs vary with secondary ligands and metal nodes. In 1 and 2, two C(1)-symmetric M(4)(HL)(4) units are bpy-bridged into dimeric chiral nanomolecules with two different cavities. As deprotonated with NaOH, the combination of Ni(II) and HL forms a pseudo-S(4)- or S(4)-symmetric M(4)(HL)(4), which further assembles into 1D chiral crystals 3 or rare 3D crystals 4 of bpy-bridged 5-fold interpenetrating diamondoid architecture with metallacalix[4]arene building blocks as novel 4-connecting nodes, and the combination of Cd(II) and HL forms an 8-connected C(2)-symmetric M(4)(HL)(4) that fabricates the alpha-Po net of 5. Notably, those large M(4)(HL)(4) units are potentially highly connected building blocks in a hierarchical assembly of metal-organic networks. Magnetic studies disclose antiferromagnetic interactions in M(4)(HL)(4) of 1-4. The magnetic data for 1, 3, and 4, all containing isomeric Ni(4)(HL)(4) units, are analyzed by an equilateral quadrangle isotropic model combined with the molecular-field approximation with J = -4.00(2), -3.39(2), and -2.72(3) cm(-1), respectively, presenting a stronger comparison between the structure and magnetism. The emission of 5 is odd, which perhaps is relative to the bichelating fashion of ligand HL and a rare coordination geometry of Cd(II). Moreover, the thermal stability and gas sorption properties of these compounds were measured.

Poly[(μ2-3,6-di-4-pyridyl-1,2,4,5-tetrazine)(μ2-thiocyanato)copper(I)

The title compound, [Cu(NCS)(C12H8N6)]n, is a self-assembled two-dimensional metal–organic network. The Cu atom is linked by two N atoms from two 3,6-di-4-pyridyl-1,2,4,5-tetra­zine ligands and by the N and S atoms from two thio­cyanate ligands in a distorted tetra­hedral environment. The Cu atom and the thio­cyanate ligand occupy a crystallographic mirror plane m, and a crystallographic inversion centre is in the middle of the tetra­zine ring, generating the zigzag fashion of the two-dimensional network. The infinite –Cu—SCN—Cu—SCN– chain is due to translational symmetry along the a axis. These chains are further connected through the 3,6-di-4-pyridyl-1,2,4,5-tetra­zine ligands that bridge the CuI centers, generating a two-dimensional network. There are π—π stacking inter­actions between the pyridine and tetra­zine rings (perpendicular distances of 3.357 and 3.418 Å), with a centroid–centroid distance of 3.6785 (16) Å.