Brick-wall Network Research Articles

A fluorescent covalent organic framework with a brick-wall topology for the detection of Cu2+ promoted by the associated mechanism

Fluorescent covalent organic frameworks have initially drawn considerable attention as they show the excellent porous performances as well as highly selective fluorescent properties. However, the relationship between the porous structure and response mechanism is still an unmet challenge up to date. Herein, a Schiff-base two-dimensional covalent organic framework (2D COF) (PI-TPA COF) with rarely brick-wall network was constructed by concentrating a tritopic T-shaped building block and a ditopic linear linker. Its brick-wall AB stacking structure was characterized in detailed by powder X-ray diffraction analysis, FT-IR, nitrogen adsorption−desorption measurements as well as theoretical simulations. PI-TPA COF exhibited the highly selective fluorescent performance for Cu2+ (detection limit of 0.03 nmol L−1) in the mixture of acetonitrile/water (v/v = 7:3), which was mainly ascribed to the associated mechanisms of the absorption competition quenching (ACQ) caused by the porous structure of PI-TPA COF and the coordination interaction between PI-TPA COF and Cu2+. Furthermore, PI-TPA COF was successfully applied to the detection of Cu2+ in the real environmental water, which provides a new platform for the application of COF materials in the field of environmental protection.

Surface-Confined Self-Assembly of Asymmetric Tetratopic Molecular Building Blocks.

Surface-confined self-assembly of functional molecular building blocks has recently been widely used to create low-dimensional, also covalent, superstructures with tailorable geometry and physicochemical properties. In this contribution, using the lattice Monte Carlo simulation method, we demonstrate how the structure-property relation can be established for the 2D self-assembly of a model tetrapod molecule with reduced symmetry. To that end, a rigid functional unit comprising a few interconnected segments arranged in different tetrapod shapes was used and its self-assembly on a triangular lattice representing a (111) crystal surface was simulated. The results of our calculations show strong dependence of the structure formation on the molecular symmetry, in particular on the (pro)chiral nature of the building block. The simulations predicted the formation of unusual ordered racemic networks with unique aperiodic spatial distribution of the surface enantiomers. Molecular symmetry was also found to have significant influence on the enantiopure self-assembly which resulted in the Kagome and brickwall networks and other less ordered extended superstructures with parallelogram pores. The theoretical findings of this contribution can be relevant to designing and on-surface synthesis of molecular superstructures with predefined geometries and functions. In particular, the predicted molecular architectures can stimulate experimental efforts to fabricate and explore new nanostructures, for example graphitic, having the composition and geometry proposed in our study.

Ph-Directed Assembly of Two 2D Copper(II) Coordination Polymers Based on Mixed Benzenetetracarboxylate and 1,4-bis(1,2,4-triazole-1-ylmethyl)-2,3,5,6-Tetrafluorobenzene Ligands: Syntheses, Structures and Properties

Two new Cu(II) coordination polymers [Cu(Fbtx)(H2btec)(H2O)2]n and {[Cu(Fbtx)(btec)0.5(H2O)2]·H2O}n have been synthesised by hydrothermal reactions of Cu(II) nitrate with 1,4-bis(1,2,4-triazole-1-ylmethyl)-2,3,5,6-tetrafluorobenzene (Fbtx) and 1,2,4,5-benzenetetracarboxylic acid (H4btec) under different pH conditions. The first complex has a two-dimensional four-connected layer structure with a 44-sql topology, whereas the second has a two-dimensional three-connected brick-wall network. The luminescence properties of the complexes in the solid state and their thermal stabilities have also been studied.

Four new coordination polymers constructed using 2,2′-oxybis(benzoic acid) and auxiliary N-donor ligands: Syntheses, structures, magnetic behavior and DFT studies

Four new coordination polymers [Cu(oba)(phen)] (1), [Co(oba)(phen)] (2), [Ni2(oba)2(bpe)] (3) and [Ni(oba)(bpe)1.5]·2.5H2O (4) [H2oba=2,2′-oxybis(benzoic acid), phen=1,10-Phenanthroline, bpe=1,2-bis(4-pyridyl)ethylene] were synthesized by hydrothermal reactions and characterized by single-crystal X-ray diffraction, thermogravimetric analyses, IR spectroscopy and elemental analysis. Compound 1 shows a discrete binuclear structure. Compound 2 is a right-handed 1D helical chain, though π–π stacking interactions to form a 2D wavelike network. Compound 3 displays a 2D wavy layer with the paddle-wheel SBUs. Compound 4 features a 2-fold interpenetrating 3D structure with 2D brick-wall networks. The magnetic properties of compounds 1, 2 and 4 have also been investigated. According to the crystal structures, the full geometry optimizations of compounds 1–4 were carried out by using hybrid DFT methods at B3LYP/6-31G(d) level. Meantime, the DFT-BS approach was applied to study the magnetic coupling behavior for compounds 1, 2 and 4, the result reveals that the calculated exchange coupling constants J were in good agreement with the experimental data.

Old dog, new tricks: 2,2′-biphenol as a bridging and book-end ligand in discrete and extended Co(ii) architectures

We report the first Co(II) based discrete and extended network materials comprising the 2,2′-biphenol ligand. We first present the synthesis and magnetic characterisation of the Co(II) dinuclear complexes [Co(II)2(L)2(py)4]·2EtOH (1) and [Co(II)2(L)2(4-pic)4].2LH2 (2), both of which exhibit antiferromagnetic exchange between their Co(II) centres. The introduction of the co-ligand 2-hydroxypyridine (2-hpH) leads to the production of planar octametallic complex [Co(II)8(OMe)2(L)4(LH)2(2-hp)4(MeCN)4]·MeCN (3). Magnetic susceptibility and magnetisation measurements on 3 indicate dominant ferromagnetic exchange between the Co(II) centres. We also describe the first Co(II)/2,2′-biphenol extended networks in the shape of the 1D coordination polymer {[Co(II)(LH)(4,4-tmdp)2(NO3)](LH2)}n (4) (where 4,4′-tmdp = 4,4′-trimethylenedipyridine) and the 2D brickwall network [Co(II)(LH)(trans-bpe)1.5(NO3)] (5) (where trans-bpe = trans-1,2-bis(4-pyridyl)ethylene), comprising T-shaped nodes.

A two-dimensional coordination polymer with a brick wall structure: Synthesis, crystal structure, and properties of a nickel(II) hexaazamacrocyclic complex with azido ligand

A 2D hexaazamacrocyclic complex trans-[Ni(hto)(N 3) 2] ( 2) (hto = 1,3,6,9,11,14-hexaazatricyclo[12.2.1.1 6,9]octadecane) was synthesized from the mononuclear fragment [Ni(hto)]Cl 2·2H 2O ( 1) and sodium azido in methanol solution. The crystal structure of complex 2 is centrosymmetric and the nickel(II) atom has an axially elongated octahedral geometry with four nitrogen atoms from the hexaazamacrocycle and two nitrogen atoms from the azido ligands. Each trans-[Ni(hto)(N 3) 2] unit extends its structure to form a 2D brick wall network based on hydrogen bonding interactions between the nitrogen atoms of azido ligands and the secondary amine of the macrocycle in neighboring four units. Complex 2 exhibits blue fluorescent emission in the solid state at room temperature.

Guest-Induced Isomerization of Net and Polymorphism in Trimesic Acid–Arylamine Complexes

Two molecular complexes of 1,3,5-benzenetricarboxylic acid (BTA) with 4,4′-methylenebis(2,6-dimethylaniline) (MBDA) and 2,6-dimethylaniline (DMA) led to the formation of two host guest systems. The MBDA species get trapped in hexagonal channels produced within the crystal lattice of the BTA. On the other hand, the DMA guest moieties are encapsulated into the channel formed by the brick wall network of BTA and water molecules. Isomerization of the (6,3) net, from hexagonal to brick wall, occurs due to the extra flexibility in the cluster of DMA guests which led to the additional hydrogen bonds with the host framework and incorporation of water molecules into the net. Each system contains two BTA species in the asymmetric unit with different ionic states, indicating that the proton transfer depends also upon the solid state environment. Crystallization of the BTA and MBDA mixture with different concentrations produces solvates of BTA–MBDA complex and MBDA crystallizes out in two forms depending upon the BTA...

Structural diversity in two dimensional chiral coordination polymers involving 4,4′-bipyridine and l-cysteate as bridging ligands with Zn and Cd metal centres: Synthesis, characterization and X-ray crystallographic studies

Two chiral coordination polymers involving amino acid backbone l-cysteic acid (H 2 l-cys) and N-donor ligand 4,4′-bipyridine (4,4′-bpy) [{Cd( l-cys)(4,4′-bpy)(H 2O)}3.5H 2O] n 1, [{Zn 2( l-cys) 2(4,4′-bpy) 2(H 2O) 4}·(H 2O)·(4,4′-bpy)] n 2 with rectangular grids have been synthesized. Both compounds are insoluble in common polar/non-polar solvents and well characterized by various physico-chemical techniques such as CHN, IR, TGA, NMR, solid state CD and single crystal X-ray diffraction methods. Complexes 1 and 2 comprise l-cysteate dianions self assembled into chiral coordination polymers by bridging the adjacent metal centres through the carboxylate oxygen generating one-dimensional helical chains. The helical chains are pillared by 4,4′-bpy generating two dimensional network. Complex 1 generates two dimensional (4,4) rectangular grid network with dimension 4.77 Å × 11.74 Å (based on d Cd···Cd) involving with the edge sharing l-cys and 4,4′-bpy ligands, respectively. Complex 2 possesses a brick-wall type (6,3) network topology with edge lengths of the grids 11.42 Å × 10.11 Å based on d Zn···Zn. Lattice water molecules are encapsulated between the adjacent rectangular grids via hydrogen bonding interactions. One 4,4′-bpy moiety is stacked between the adjacent layers of brick-wall network via weak π···π interaction with the edge sharing N-donor ligand. Even though both the complexes are rigid and stable, N 2 adsorption studies by these complexes revealed not much promising results. The terminal protruding sulphonate groups, angular orientation of the grids within the two-dimensional network and interpenetration of the adjacent offset sheets concomitantly prevent the formation of through tubular channels. Flexible coordination geometry around the metal centre and the versatile coordination mode of the amino carboxylate group from the l-cys moiety are accountable for the variation of the appealing network topology in these complexes. Chiral nature is established by solid state CD spectrum which shows a positive cotton effect for both complexes.

A Doubly Interpenetrated Layer Structure: 4-Acetamidobenzaldehyde 4-Nitrophenylhydrazone

The title molecule, 4-acetamidobenzaldehyde 4-nitrophenylhydrazone, is essentially planar with the maximum deviations from the least-squares plane through the 22 non-hydrogen atoms being 0.176(1)angstrom (nitro-O) and -0.152(1) angstrom(amide-O). The dihedral angle between the benzene rings is 6.93(7)degrees. The conformation about the C=N bond is E. The presence of amide-H center dot center dot center dot O-nitro and hydrazine-H center dot center dot center dot O-amide hydrogen bonding leads to the formation of zigzag 2-D arrays with a pseudo three-connected brick-wall network when viewed normal to the plane of the layer. The layers are sustained by 38-membered {center dot center dot center dot OCNC5N2C4NO center dot center dot center dot HNCO center dot center dot center dot HN2C5NH center dot center dot center dot ONC4NH} synthons and the rather large voids defined by these are occupied by a centrosymmetrically related layer to result in the formation of a doubly interpenetrated network. These stack along the b direction being connected by C-H center dot center dot center dot O interactions. The compound crystallizes in the monoclinic space group P2(1)/c with a = 10.8152(3) angstrom, b = 10.9469(2) angstrom, c = 12.9198(4) angstrom, beta = 113.679(1)degrees, and Z = 4.

Cationic induced assembly of two 2D zinc–terephthalate polymeric networks

Based on templates of [Ph 3PCH 2Ph]Cl and [Ph 4P]Cl ([Ph 3PCH 2Ph] = benzyltriphenylphosphonium, [Ph 4] = tetraphenylphosphonium), the hydrothermal reactions of zinc acetate dihydrate, H 2tp (tp = terephthalate) and water give rise to two new zinc–terephthalate coordination polymers, [Ph 3PCH 2Ph][Zn(tp)Cl] ( 1) and [Ph 4P][Zn(tp)(H 2O) 2·0.5tp] ( 2). X-ray single-crystal structural analysis reveals that both 1 (C 33H 26ClO 4PZn) and 2 (C 36H 30O 8PZn) crystallize in the 2D non-interpenetrating layered supramolecular networks with guest organophosphonium cations. Due to template effect of different guest cations, 1 presents an interesting 2D smectite-like lamellar framework that formed by the 4-linked (4,4) anionic zinc–terephthalate polymeric network and the interlayer [Ph 3PCH 2Ph] + exchangeable cations, while 2 shows a 2D 3-linked (6,3) H-bonded anionic zinc–terephthalate polymeric brickwall network with encapsulated guest [Ph 4P] + cations. Both compounds are stable up to about 300 °C, and exhibit intense fluorescent emission band at 446 nm ( λ exc = 328 nm) for 1 and 420 nm ( λ exc = 340 nm) for 2 in the solid state at room temperature.

A 2D brickwall architecture from a double-T-shaped ligand and hybrid coordinatively unsaturated copper: Synthesis, structure, and framework dynamic

A double-T-shaped ligand (H 4BPTC) as the spacer has been first used to direct the assembly of a 2D coordination polymer with brickwall network topology, [Cu 2(BPTC)(Im) 4(H 2O)(DMF)] n ( 1) (DMF = N,N-dimethylformamide, H 4BPTC = Biphenyl-3,3′,4,4′-tetracarboxylic acid, Im = imidazole), which exhibits an interesting framework dynamic upon de-/resolvation.

Cluster-based copper(ii) coordination polymers with azido bridges and chiral magnets

Three homochiral layered complexes, [Cu3(R-chea)2(N3)6]n (1), [Cu3(S-chea)2(N3)6]n (2) (chea = 1-cyclohexylethylamine) and [Cu3(S-phpa)2(N3)6]n (3) (phpa = 1-phenylpropylamine), and three novel cluster-based coordination polymers, [Cu6(1,2-pn)4(N3)12]n (4) (1,2-pn = 1,2-diaminopropane), [[Cu8(en)4(N3)16] x H2O]n (5) (en = ethylenediamine) and [Cu6(N-Ipren)2(N3)12]n (6) (N-Ipren = N-isopropylethylenediamine), have been synthesized by the self-assembly reactions of Cu(NO3)2 x 3H2O, NaN3 and small organic amine ligands. Their crystal structures are determined by single-crystal X-ray diffraction. Complexes are composed of neutral 2D brick wall networks with only end-on azido bridges. Complexes and are 3D coordination polymers featuring copper-azido clusters and [Cu(diamine)2]2+ units which are linked by the azido bridges. Complex is a 3D coordination framework based on the hexanuclear copper(II) clusters [Cu6(N3)12(N-Ipren)2]. Magnetic studies show that complexes are interesting chiral ferromagnets with the magnetic transition temperature at ca. 5.0 K. Complexes and show ferromagnetic coupling in the copper-azido cluster units and antiferromagnetic interaction between neighboring units, while complex shows ferromagnetic ordering at 3.2 K.

A 2D coordination polymer with brick-wall network topology based on the [Cu(NCS) 2(pn)] monomer

The new complex [Cu(NCS) 2(pn)] ( 1) (pn = 1,3-propanediamine) has been synthesized and characterized by elemental analysis, infrared and electronic spectroscopy. Single crystal X-ray diffraction studies revealed that complex 1 is made up of neutral [Cu(NCS) 2(pn)] units which are connected by μ-1,3,3-thiocyanato groups to yield a 2D metal-organic framework with a brick-wall network topology. Intermolecular hydrogen bonds of the type NH⋯SCN and NH⋯NCS are also responsible for the stabilization of the crystal structure.

Supramolecular assembly of one-dimensional channels and two-dimensional brick-wall networks from asymmetric dithioether ligands and copper(I) iodide

Two asymmetric dithioether ligands with cyclohexyl (L1) and phenyl (L2) end-groups were synthesized. Reaction of L1 with copper(I) iodide afforded a 1D channel-type coordination polymer {[Cu4I4(L1)2](CH3CN)0.5}n (1) interconnected by cubane-type tetranuclear Cu4I4 cluster units. Whereas, a 2D brick-wall-type coordination polymer [CuI(L2)]n (2) with rhomboid dinuclear Cu–I2–Cu nodes was isolated from the reaction of L2 with copper(I) iodide.

Three-fold parallel interlocking of 2-D brick-wall networks showing ladder-like unsymmetrical Borromean links

Reaction of a semi-rigid ditopic ligand, N,N′-bis(4-pyridylmethyl)pyromellitic diimide (L), with HgI2 afforded the 2-D brick-wall type (6,3) networks, which interlocked in a parallel fashion to give the first example of unsymmetrical Borromean ladder links.

Metal-Controlled Assembly of Coordination Polymers with the Flexible Building Block 4-Pyridylacetic Acid (Hpya)

Self-assembly of a flexible building unit 4-pyridylacetic acid (Hpya) with inorganic metal salts Cu(ClO4)2·6H2O, Co(OAc)2·4H2O, Ni(ClO4)2·4H2O, AgNO3, and HgCl2 affords five new metal−organic coordination frameworks [M(pya)2(H2O)2]n (pya = 4-pyridylacetate; M = Cu for 1; Co for 2; and Ni for 3), [Ag(pya)]n (4), and [Hg(pya)Cl]n (5) under similar reaction conditions. Single-crystal X-ray diffraction analyses of these polymeric complexes suggest that 1−3 are isostructural and exhibit a two-dimensional (2D) wavelike layered architecture constructed by alternate left- and right-hand helical chains, in which pya takes the bidentate (Npy, OCOO-) bridging mode. However, polymer 4 possesses a three-dimensional (3D) brickwall network generated from the expansion of 2D layers with dinuclear [Ag2(RCOO)2] nodes via further interlayer Ag−OCOO- interactions, which is also stabilized by argentophilic interactions (Ag···Ag = 2.983(3) Å). The structure of 5 seems more complicated, in which the [Hg2(pya)2] boxlike dimeric subunits are extended to a unique 3D framework via multiple Hg−OCOO- coordination forces. In the structures of 4 and 5, the carboxylate groups display unusual μ-O, O‘syn-μ-O, O and μ-O, O-η-O, O‘-μ-O‘, O‘ binding modes, respectively. The significant differences of these metal−organic frameworks indicate that the flexible pya ligand may adjust its coordination fashion to meet the requirement of the coordination preference of the metal center. The fluorescent and thermal properties of these new materials have also been studied.

Nonpenetrating Architectures of Cd(II) Complexes Constructed by Bispyridyl-Substituted Diphthalic Diimide Ligands of Varied Geometry

New bispyridyl ligands N,N'-bis(3-pyridylmethyl)-diphthalic diimide (L 1 ) and N,N'-bis(3-pyridylmethyl)-oxydiphthalic diimide (L 2 ) were synthesized. Their coordination polymers [Cd(L 1 ) 1.5 (NO 3 ) 2 ] n .nCHCl 3 (1) and [Cd(L 2 ) 2 (NO 3 ) 2 ] n . nEtOH (2) have either a 2D (6,3) brick-wall network with L 1 in both Z t - and U t -modes or a ID chain of layered double-bridging Cd 2 L 2 2 units with solely angular L 2 . The connection of the diimide moieties supplemented by the rich hydrogen bonding prevents interpenetration in 3D networks.

Structural diversity in the Cu(pyrazinecarboxylate)2/CdCl2 system: new one-, two- and three-dimensional mixed metal coordination polymers

Four new inorganic–organic polymeric materials have been synthesized by reacting the metal containing building block, Cu(pyzca)2, with cadmium chloride. All resulting polymers have both metals incorporated in the structure and display a variety of structural motifs, ranging from one-dimensional chains to complicated three-dimensional networks. The first compound, [Cu(Pyzca)2(H2O)CdCl2(H2O)·H2O]n (1) is a one-dimensional double chain. The next two compounds, [Cu(Pyzca)2(H2O)2Cd2Cl4(H2O)2]n (2) and [Cu(Pyzca)2(H2O)Cd2Cl4(H2O)2·3H2O]n (3), assemble in a two-dimensional brick-wall network, while the fourth, [Cu(Pyzca)2Cd2Cl4]n (4), features an intricate three-dimensional network. Synthesis, X-ray structure determinations, and the influence of water molecules coordinated to the copper centers on the coordination geometry and overall extended structure are discussed.

Supramolecular synthesis of brick wall and honeycomb networks from the T-shaped molecule 5-nitrosalicylic acid

The T-geometry of O–H⋯O and C–H⋯O hydrogen bonding groups in the title molecule (5-NSA) form a brick wall network that is modularly expanded and transformed to chair cyclohexane and honeycomb architectures in molecular complexes with trans-1,4-dithiane-1,4-dioxide and dioxane. The variation in hydrogen bond synthons results in different examples of topologically related (6,3) nets.

Synthesis, structures and photoluminescence of three terbium(iii) dicarboxylate coordination polymers

Three polymeric terbium(III) complexes of 4,4′-oxybis(benzoic acid) (H2oba) have been hydrothermally synthesised with different metal∶carboxylate ratios or in the presence of an additional chelate ligand 2,2′-bipyridine (2,2′-bpy) and characterised by single-crystal X-ray diffraction. In [Tb(oba)(Hoba)(H2O)2)·H2O, 1, the metal atoms are bridged by the oba/Hoba carboxylate groups into one-dimensional covalent chains, which are further interconnected by the oba ligands to produce a two-dimensional brick-wall network. In [Tb2(oba)3(H2O]4], 2, the metal atoms are bridged by the oba/Hoba carboxylate groups into one-dimensional covalent chains different from those in 1, which are further interconnected by the oba ligands to produce a two-dimensional condensed network. In the structure of [Tb2(oba)3(2,2′-bpy)2], 3, there are centrosymmetrical tetrakis(μ-carboxylate)-bridged Tb(III) dimeric structural subunits, which are interlinked by the oba ligands into a three-dimensional framework. The three compounds exhibit interesting photoluminescence at room temperature. The results show that different metal∶carboxylate ratios can influence the polymeric structures and that the presence of 2,2′-bpy ligand alters not only the topology of the framework from two-dimensional to three-dimensional, but also the photoluminescent properties in both intensity and lifetime.