Tetranuclear Zinc Clusters Research Articles

Dual Emission with Efficient Phosphorescence Promoted by Intermolecular Halogen Interactions in Luminescent Tetranuclear Zinc(II) Clusters.

The development of Zn-based phosphorescent materials, associated with a ligand-centered (LC) transition, is extremely limited. Herein, we demonstrated dual emissions including fluorescence and phosphorescence in luminescent tetranuclear Zn(II) clusters [Zn4LI4(μ3-OMe)2X2] (HLI = methyl-5-iode-3-methoxysalicylate; X = I, Br, Cl), incorporating iodine-substituted ligands. Single-crystal X-ray structural analyses and variable-temperature emission spectra studies revealed the presence of iodine substitutions, and intermolecular halogen interactions produced the internal/external heavy-atom effects and yielded strong green phosphorescence with a long emission lifetime (λmax = 510-522 nm, Φem = 0.28-0.47, τav = 0.78-0.95 ms, at 77 K). This work provided a new example that the introduction of halogen interactions is an advantageous approach for inducing phosphorescence in fluorescent metal complexes.

Construction of a 3-D pillar-layered coordination polymer from an Sql network

The rational design and systematic synthesis of a “pillar-layered” coordination polymer was carried out using a rigid carboxylic acid, 2-hydroxy-trimesic acid (H4L), resulting in two coordination polymers, {[Zn4(L)2(DMA)3(H2O)5]·H2O} n (1) and [Zn4(L)2(pdp)(H2O)4] n (2). Compound 1 is a two-dimensional (2-D) network containing tetranuclear zinc clusters, deprotonated H4L ligands and DMA solvent molecules. The introduction of trans-1,2-bis(4-pyridyl)ethylene) (pdp) replaced solvent molecules in 1, forming pillars between the 2-D sheets to furnish 2. The water stability of 2 is higher than that of 1. The powder X-ray diffraction, thermal stabilities, and solid-state luminescence properties also have been investigated for 1 and 2.

Exclusive Recognition of Acetone in a Luminescent BioMOF through Multiple Hydrogen-Bonding Interactions.

An anionic microporous metal-organic framework (1), featuring a combination of mononuclear and tetranuclear zinc clusters and a mix-and-match strategy of two different types of organic ligands, has been successfully constructed via a solvothermal reaction. Its luminescence can be exclusively quenched by acetone. In situ single-crystal X-ray diffraction studies reveal the specific acetone binding sites and the existence of multiple hydrogen bonds between acetone and the framework. Together with its chemical and thermal stability, 1 has been demonstrated to be a potential luminescence probe for the rapid detection of acetone with a remarkable anti-interference and a low detection limit (1.85 ppm).

A new anionic metal-organic framework based on tetranuclear zinc clusters: Selective absorption of CO2 and luminescent response to lanthanide (III) ions

A new anionic metal-organic framework, {[H3O]2[Zn4(μ4-O)(NSBPDC)4]·16(H2O)]}n (1), was synthesized under solvothermal conditions using a predesigned multifunctional dicarboxylic acid (H2NSBPDC = 6-nitro-2,2′-sulfone-4,4′-dicarboxylic acid). Complex 1 contains 4-connected tetrahedral [Zn4(μ4-O)(CO2)8] clusters, which are further linked by the bridging ligands, generating a threefold interpenetrated diamond-like network with ultra-microporous channels. Gas adsorption studies reveal that 1 has good adsorption selectivity for CO2 over CH4 and N2. In addition, 1 can serve as a host to incorporate lanthanide cations via a targeted ion-exchanged process. Notably, the structure of 1 can be dehydrated and rehydrated reversibly.

Effect of Benzenetricarboxylic Ligands on the Construction of Zn(II) Coordination Polymers Based on a Flexible Imidazole‐Based Ligand

AbstractTwo 3D Zn(II) networks based on 1,4‐bis(2‐methylimidazol‐1‐ylmethyl)‐2,3,5,6‐tetramethylbenzene (bmimx), namely, {[Zn4(μ4‐O)(μ2‐H2O)(1,3,5‐BTC)2(bmimx)]⋅H2O}n (1) and {[Zn2(μ2‐OH)(1,2,4‐BTC)(bmimx)(H2O)]⋅2.5H2O}n (2) (1,3,5‐H3BTC=1,3,5‐benzenetricarboxylic acid, 1,2,4‐H3BTC=1,2,4‐benzenetricarboxylic acid) have been prepared at hydrothermal condition by varying the benzenetricarboxylic ligands. Single‐crystal X‐ray diffraction indicates that complex 1 shows a (3,8)‐connected net based on tetranuclear zinc(II) clusters; complex 2 shows a 8‐connected framework based on 18‐membered tetranuclear zinc(II) macrometallacycles. The results indicate that benzenetricarboxylic ligands have an important effect on the stuctural characters and ultimate frameworks. Moreover, the photoluminescence properties of the two complexes were studied in the solid state at room temperature.

Two novel tetranuclear zinc(II) clusters with different topological structures: Crystal structures and luminescence properties

Two novel tetranuclear zinc(II) clusters with different topological structures have been synthesized by using Zn(ClO4)2·6H2O, sodium azide and potentially multidentate Schiff base ligands containing different substituent groups. The two complexes have been characterized by elemental analysis, IR, single crystal X-ray diffraction and fluorescence studies. Structural studies reveal that [Zn4(HL1)4(μ1,1-N3)2(N3)2] (1) is a linear tetranuclear cluster whereas [Zn4(HL2)4(μ1,1-N3)4] (2) is a square-planar tetranuclear cluster. Both two complexes display intraligand (π→π*) fluorescence. Due to the heavy atom effect which increases the probability for intersystem crossing to the triplet state, the fluorescence intensity of complex 2 is much lower than that of complex 1.

In situ hydrothermal synthesis of a twofold entangled coordination network based on tetranuclear zinc(II) clusters: An experimental and theoretical study

A new 2D coordination polymer, Zn2(OH)(SDBA)(PTZ) (1), (H2SDBA=4,4′-dicarboxybiphenyl sulfone, PTZ=5-(4-pyridyl)tetrazolate) was synthesized via in situ hydrothermal reaction of zinc(II) salt, NaN3, 4-cyanopyridine and H2SDBA, and characterized by elemental analysis, IR, X-ray powder diffraction (XPRD) and single crystal X-ray diffraction. The structure of complex 1 shows a 2D twofold entangled network with (4, 4) topology based on the tetranuclear zinc(II) clusters, which contains unusual both polyrotaxane and polycatenane characters, and further forms a 3D supramolecular architecture by weak π⋯π stacking interactions. Meanwhile, the nature of coordinate bonds in complex 1 has been deeply investigated by high level theoretical calculations. The result of theoretical computation indicates that all coordinate bonds are basically intermediate and covalent dominant interactions in complex 1, and complex 1 has the high thermal stability, which coincides with the result of thermogravimetric analysis (TGA) of complex 1. The photoluminescent property of complex 1 has also been investigated in the solid state at ambient temperature.

Stepwise tuning of the substituent groups from mother BTB ligands to two hexaphenylbenzene based ligands for construction of diverse coordination polymers

Hexaphenylbenzene based tritopic carboxylate ligands H3L1 (1,3,5-tris(4-carboxyphenyl)-2,4,6-tris(4-tert-butylphenyl)benzene) and H3L2 (1,3,5-tris(4-carboxyphenyl)-2,4,6-triphenylbenzene) were applied to synthesize six coordination polymers (CPs) {[Zn4(L1)2(μ2-OH)2(DMA)4(H2O)]·(C2H6O)2(H2O)}n (1), {[Cd3(L1)2(μ2-H2O)2(H2O)4(DMF)2(C2H6O)]·(DMF)(H2O)(C2H6O)2}n (2), {[Cd(L1)(C2H6O)]·(H3O+)(DMF)(C2H6O)}n (3), {[Co3(L1)2(μ2-H2O)(H2O)6(DMF)2(C2H6O)]·(DMF)3}n (4), {[Mn3(L1)2(H2O)5(DMF)4(C2H6O)]·(C2H6O)}n (5), and {[Zn2(L2)Cl(H2O)(DMA)]·(DMA)2(H2O)}n (6) (DMF = N,N-dimethylformamide, DMA = N,N-dimethylacetamide). The CPs were characterized by single crystal X-ray diffraction, infrared spectra (IR), elemental analyses, powder X-ray diffraction (PXRD), and thermogravimetric analyses (TGA). 1 and 2 exhibit two-dimensional (2D) honeycomb bilayer structures based on tetranuclear zinc or trinuclear cadmium clusters. 3 is PH-induced supramolecular isomer with 2, featuring 2D corrugated honeycomb structure. In 4 and 5, only two carboxylate groups coordinate with trinuclear metal clusters to form 1D coordination chains. The chains are further connected through hydrogen bonds between the left carboxylate groups and coordination water molecules to form honeycomb bilayer sheets. 6 exhibits 2D planar honeycomb structure based on Zn2(COO)3 clusters. The different topological networks 1 and 6 are constructed from structurally similar ligands H3L1 and H3L2, showing that structural diversity could be realized by adjusting substituent groups on organic ligands. The photoluminescent behaviours of compounds 1, 2, and 6 and magnetic properties of 4 and 5 were also investigated.

Hydrothermal syntheses, crystal structures and luminescence properties of zinc(II) coordination polymers constructed by bifunctional 4′-(4-carboxyphenyl)-3,2′:6′,3″-terpyridine

Four polymeric frameworks, [Zn(cptpy)2(Hcptpy)2]·2H2O (1), [Zn(cptpy)Cl]n (2), [Zn4(cptpy)2(3-btc)2]n·nH2O (3) and [Zn2(cptpy)(2-btc)]n (4), (Hcptpy=4′-(4-carboxyphenyl)-3,2′:6′,3″-terpyridine, H3(3-btc)=1,3,5-benzenetricarboxylic acid, H3(2-btc)=1,2,4-benzenetricarboxylic acid) have been hydrothermally synthesized and characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction analyses. Compound 1 has a mononuclear structure, while 2 shows a one-dimensional ladder chain containing 28 member rings with (cptpy)− anions as bridges. For compounds 1 and 2, weak hydrogen bonding and intra- and/or inter-molecular π⋯π stacking interactions link the mononuclear or infinite chain structures into high-dimensional supramolecular structures. Compound 3 reveals a (4,4,4)-connected three-dimensional (3D) framework. Compound 4 is a three dimensional network structure comprised of new tetranuclear zinc clusters, exhibiting a {4·6·8}{42·6·83}{42·62·82}{43·62·85} topological structure. In addition, the thermal stabilities and photoluminescence properties of 1–4 were also studied.

Two zinc(II) coordination polymers based on a benzenedicarboxylic acid derivative: Synthesis, crystal structures and luminescent properties

Abstract Two new coordination polymers, {[Zn 3 L 2.5 ( μ 3 -OH)(H 2 O) 3 ]·4H 2 O} n ( 1 ) and [Zn 2 L 1.5 ( μ 3 -OH)(4,4′-bpy) 0.5 ] n ( 2 ) (H 2 L = 2,5-bis(4-methylbenzoyl)terephthalic acid, 4,4′-bpy = 4,4′-bipyridine), have been hydrothermally synthesized and characterized by elemental analysis, IR spectroscopy, TG, PXRD and single crystal X-ray diffraction. Complex 1 possesses a 2D double-layer configuration with 4 8 ·6 2 network constructed with trinuclear zinc(II) clusters and L 2− ligands, which extends into a 3D architecture via O–H···O interactions between coordinated water molecules and lattice water molecules. Complex 2 is a uninodal 8-connected 3D framework with a 4 24 ·6 4 network based on tetranuclear zinc(II) clusters as nodes. Moreover, the luminescent properties of complexes 1 and 2 were also investigated.

Two multi-dimensional frameworks constructed from zinc coordination polymers with pyridine carboxylic acids

Two novel zinc coordination polymers [Zn 2(H 2O)L(MoO 4)] n ( 1) and [Zn 4(PO 4) 2L′(H 2O)] n ( 2) (H 2L=2,2′-bipyridine-6.6′-dicarboxylic acid, H 2L′=2,2′-bipyridine-4,4′-dicarboxylic acid) have been hydrothermally synthesized and characterized by elemental analyses, IR spectra, UV spectra, single-crystal X-ray diffraction and thermogravimetric analyses. Structural analyses indicate that 1 represents a 2-D sheet structure built by dimeric [Zn 2L(H 2O)] 2+ units and MoO 4 2– groups whereas 2 displays an interesting 3-D framework constructed by tetranuclear zinc clusters, L′ 2− ligands and PO 4 3– groups. Examination of UV spectra suggests that both 1 and 2 can stably exist in the pH range of 2.45–5.45 and 3.01–8.55 in aqueous solution, respectively. The room-temperature solid-state photoluminescence of 1 and 2 are derived from the intra-ligands π–π⁎ transitions of H 2L and H 2L′ ligands and the ligand-to-metal-charge-transfer transitions.

Crystal structure of an oxalate-bridged tetranuclear 8-hydroxyquinoline Zn(II) cluster: [Zn4Q6(Ox)]0.5n

The chain structure of a tetranuclear zinc(II) cluster [Zn4Q6(Ox)]0.5n ([Zn4 (C9H6NO)6(C2O4)]0.5n) (1) (Q = 8- hydroxyquinoline anion, Ox = oxalate dianion) was determined by X-ray crystallography and characterized by elemental analysis, IR spectroscopy and thermal analysis. It crystallizes in the monoclinic system, space group P21/n (No. 14), with the lattice parameters a = 13.2222(15) ?, b = 11.0566(12) ?, c = 16.2224(18) ?, ? = 92.1770(10)?, V = 2369.9(5) ?3, Z = 4, Mr = 607.23 g mol-1, Dc = 1.702 g cm-3. The tetranuclear zinc(II) clusters form 1D polymeric chains parallel to the b-axis. The ?-? stacking interactions involving aryl rings support the formation of the 1D polymeric structure. The neighboring polymeric chains are connected by C-H???? interactions.

Molecular tectonics of metal–organic frameworks based on ligand-modulated polynuclear zinc SBUs and aromatic multicarboxylic acids

An investigation into the molecular tectonics of metal–organic frameworks (MOFs) is reported on the basis of N-donor ligand modulated polynuclear zinc clusters and different aromatic polycarboxylic ligands. A series of three-dimensional (3D) coordination frameworks, [Zn2(BDC)1.5(L)(OH)]·H2O (1), [Zn2(BOABA)(L)(OH)]·2H2O (2), [Zn2(BOABA)(L)(OH)]·4H2O (3), [Zn3(BTC)2(OH)]·0.25H2O·[N(C4H9)4] (4) and [Zn2(BTEC)0.5(L)(OH)2] (5), were synthesized by self-assembly of zinc ions with a new N-donor ligand 4,5-diazafluoren-9-oxime (L) and the aromatic polycarboxylic ligands 1,4-benzenedicarboxylic acid (H2BDC), 3,5-bis-oxyacetate-benzoic acid (H3BOABA), 1,3,5-benzenetricarboxylic acid (H3BTC), and 1,2,4,5-benzenetetracarboxylic acid (H4BTEC). Compound 1 exhibits a twofold interpenetrated α-polonium-type network based on tetranuclear Zn clusters as six-connected vertices and BDC ligands as linkers. Compound 2 also consists of tetranuclear units, it shows a (3,6)-connected rutile network, where tetranuclear zinc clusters act as six-connected nodes and BOABA ligands act as three-connected nodes. Compound 3 is an isomer of compound 2, due to the different configuration of tetranuclear zinc, it displays a novel (3,6)-connected network with a complex (4·62)2(42·69·84) topology. In 4, the connection between the trinuclear zinc clusters and the BTC ligands results in an infinite 3D (3,6)-connected network with point symbol (4·62)(63)(4·611·83). Compound 5 constitutes a lvt net, which is built from tetranuclear clusters and BTEC as four-connected nodes, respectively. The results indicate that various polynuclear zinc clusters are modulated by L ligands combining with Zn atoms via chelation or monodentate coordination, or acting as a structure-directing agent. Meanwhile, aromatic multicarboxylic acids also play important roles in the construction of the compounds with various structures.

Self-assembly of zinc polymers based on a flexible linear ligand at different pH values: Syntheses, structures and fluorescent properties

Five novel coordination polymers, [Zn(imbz) 2] n ( 1), {[Zn(imbz) 2]·H 2O} n ( 2), [Zn(imbz)( μ 2-OH)] n ( 3), [Zn 3(imbt) 2( p-bdc) 3] n ( 4), [Zn 4( μ 3-OH) 2(imbt) 2( p-bdc) 3] n ( 5), (imbt = 4′-(imidazol-1-ylmethyl)benzonitrile, imbz − = 4′-(imidazol-1-ylmethyl)benzoate and p-bdc = terephthalic acid) have been hydrothermally prepared through systematically changing the pH values of reaction mixture, and structurally characterized by elemental analysis, IR spectroscopy and single-crystal X-ray crystallography. Compounds 1 and 2 exhibit similar 2D (4,4) grid structures, whereas compound 2 contains a right-handed helix along b-axis. Compound 3 has a distorted diamond framework which was constructed via imbz − ligands and μ 2-OH groups linking metal atoms. Compound 4 shows a 2D 6-connected network with trinuclear zinc clusters as secondary building units (SBUs), whereas 5 shows a distorted α-Po with tetranuclear zinc clusters as SBUs, in which p-bdc ligands act as bridges. Moreover, compounds 1– 5 all exhibit strong blue photoluminescence in the solid state at room temperature.

Structures and Luminescent Properties of a Series of Zinc(II) and Cadmium(II) 4,4′-Oxydiphthalate Coordination Polymers with Various Ligands Based on Bis(pyridyl imidazole) under Hydrothermal Conditions

Six coordination polymers constructed from three structurally related ligands, 1,2-bis[2-(2-pyridyl)imidazol-1-ylmethyl]benzene (L1), 1,3-bis[2-(2-pyridyl)imidazol-1-ylmethyl]benzene (L2), and 1,4-bis[2-(2-pyridyl)imidazol-1-ylmethyl]benzene (L3) have been synthesized: [Zn2(ODPT)(L1)0.5(H2O)]·3H2O (1), [Zn2(ODPT)(L2)(H2O)2]·3H2O (2), [Zn2(ODPT)L3(H2O)]·6H2O (3), [Cd2(ODPT)(L1)0.5(H2O)]·4H2O (4), [Cd(H2ODPT)(L2)]·2H2O (5), and [Cd1.5(HODPT)(L3)0.5] (6), where H4ODPT is 4,4′-oxidiphthalic acid. Their structures have been determined by single crystal X-ray diffraction analyses. All compounds are also characterized by elemental analyses, IR spectra, and thermogravimetric (TG) analyses. Compound 1 exhibits a two-dimensional (2D) layer structure with tetra-nuclear zinc clusters as building units, and intermolecular π···π stacking interactions link these sheets to a three-dimensional (3D) supramolecular structure. Compound 2 shows infinite chains and is extended into a 2D supramolecular sheet by intermolecular hydrogen bonds. The structure of 3 is built by L3 ligands connecting ODPT-Zn double-chains to a 3D network with a (42·6·102·12)(42·6)(102·12) topology. Compound 4 is isostructural with compound 1. In 5, partly deprotonated H2ODPT2− anions link the L2-Cd 24-membered rings to generate an infinite chain that extends into a 2D supramolecular sheet by intermolecular π···π stacking interactions. In 6, L3 ligands and the ether O atoms of HODPT3− anions link Cd−O chains formed by phthalic groups into a 3D network. In addition, the luminescent properties of these compounds are discussed.

How to Hide Zinc in a Small Protein

AbstractFor Abstract see ChemInform Abstract in Full Text.

Phosphor-1,1-Diselenolato Metal Complexes of Group 11 and 12

Several copper and silver clusters containing diselenophosphate ligands such as tetranuclear [Cu{Se2P(OR)2}]4, hexanuclear [Ag{Se2P(OR)2}]6, octanuclear [Cu8(μ8-Se)}Se2P(OR)2}6], [Ag8(μ8-Se)}Se2P(OR)2}6], [Cu8(μ8-X)}Se2P(OR)2}6](PF6), [Ag8(μ8-X)}Se2P(OR)2}6](PF6), decanuclear [Ag10(μ10-Se)}Se2P(OR)2}8], undecanuclear [Cu11(μ9-Se)(μ3-X)3}Se2P(OR)2}6], [Ag11(μ9-Se)(μ3-X)3}Se2P(OR)2}6], and dodecanuclear [Cu12(P2Se6)}Se2P(OR)2}8] have been isolated. All these clusters were well characterized in the solid-state and solution phase by elemental analysis, positive FAB mass spectrometry, multinuclear NMR (1H, 31P, and 77Se), and single crystal X-ray diffraction. In addition, tetranuclear zinc clusters [Zn4(μ4-Se){Se2P(OPr)2}6], and [Zn4(μ4-O){Se2P(OR)2}6] (R = Et, iPr) also are synthesized and characterized. Solution studies of both [M{Se2P(OEt)2}2]∞ and [M2{Se2P(OiPr)2}4] (M = Zn, Cd) which display a monomer-dimer equilibrium in solution were performed by VT 31P NMR in CD2Cl2.

How to Hide Zinc in a Small Protein

Small cysteine-rich proteins (metallothioneins) and related domains of some large proteins (e.g., lysine methyltransferases) bind tri- and tetranuclear zinc clusters with topologies resembling fragments of Zn(II) sulfide minerals. These clusters are ubiquitous in animals, plants, and bacteria. Bacterial metallothioneins can also contain histidines as cluster ligands and embed Zn(II) with a "treble-clef"-like finger fold. This unusual embedded Zn(II) is "hidden" and surprisingly inert toward Zn or Cd exchange. Clearly, proteins can exert fine control over both the thermodynamics and kinetics of zinc binding in thiolate clusters. Genome sequences suggest that related zinc-finger sites are common in a variety of bacteria.