Trinuclear Zn3 Research Articles

Intermolecular Catalytic Asymmetric Iodoetherification of Unfunctionalized Alkenes.

A newly prepared trinuclear Zn3-(R,S,S)-aminoiminobinaphthoxide complex (triZn-II) catalyzed the first general intermolecular asymmetric iodoetherification of unfunctionalized alkenes. Using triZn-II, the iodoetherification reaction of unfunctionalized alkenes with o-nitrophenols proceeded smoothly to give the products with up to 92.5:7.5 er, and diene substrates were converted to the products with up to 99:1 er with the formation of a meso-isomer (dl/meso = 78/22). The chiral iodoethers gave a new platform for the synthesis of chiral morpholines.

Two dimensional Zn-stilbenedicarboxylic acid (SDC) metal-organic frameworks for cyclic carbonate synthesis from CO2 and epoxides

A two-dimensional Zn-based metal-organic framework has been synthesized by using Zn(II) ions and H2SDC (4,4′-stilbenedicarboxylic acid) under solvothermal conditions. The framework having a trinuclear Zn3-(RCO2)6 SBUs connected by the 4,4′-stilbenedicarboxylic acid to form a hexagonal network, shows a two-dimensional structure and displays high thermal stability up to approximately 330 °C. The role of Zn2+ (from Zn-SDC) for epoxide activation and Br-ion (from TBABr) for ring opening of epoxide was studied for the cycloaddition reaction of CO2 and propylene oxide (PO) under ambient conditions. Zn-SDC was found catalytically efficient towards CO2-epoxide coupling under ambient reaction conditions with high selectivity towards the desired cyclic carbonates under solvent-free conditions. The effects of various reaction parameters such as catalyst loading, temperature, CO2 pressure, and time were evaluated. Zn-SDC was easily separable and reusable at least five times without any considerable loss in the initial activity. A plausible reaction mechanism for the cycloaddition reaction was also proposed based on literature and experimental inferences.

A new three-dimensional Zn2 + coordination polymer constructed from oxalate and 1,2,4-triazolate

A new 3-D Zn2+ coordination polymer (CP) [(CH3)2NH2]3[Zn6(ox)4.5(trz)6]⋅4H2O (ox=oxalate; trz=1,2,4-triazolate) 1 was obtained by a simple solvothermal self-assembly. The crystal structural analysis demonstrates that the trz molecules link the Zn2+ ions into a two-dimensional (2-D) layer network, which is based on the trinuclear Zn3(trz)6 clusters. The ox molecules serve as the linkers to propagate the 2-D layers into a three-dimensional (3-D) network of 1. The thermogravimetry (TG) behavior, photoluminescence property, and the sensing ability of 1 are investigated. The sensing experiment on nitrobenzene (NB) reveals that 1 can serve as a fluorescence probe to detect NB at the ppm concentration.

Homo- and Heteropolynuclear Clusters of Phosphine Triphenolates.

The synthesis and structural characterization of a series of homo- and heteropolynuclear clusters constructed with a potentially tetradentate phosphine triphenolate ligand are presented. Treatment of tris(3,5-di-tert-butyl-2-hydroxyphenyl)phosphine (H3[O3P]) with 3 equiv of nBuLi in diethyl ether at -35 °C affords hexanuclear Li6[O3P]2(OEt2)2 (1) as colorless crystals. In situ lithiation of H3[O3P] with 3 equiv of nBuLi in THF at -35 °C followed by metathetical reactions with MnCl2 or NiCl2(DME) gives crystals of forest green pentanuclear MnLi4[O3P]2(THF)3 (2) or dark brown tetranuclear Ni2Li2[O3P]2(THF)2 (3), respectively. Alkane elimination of ZnR2 (R = Me, Et) with H3[O3P] in THF at 25 °C generates high yields of colorless crystalline trinuclear Zn3[O3P]2(THF)2 (4). The cluster structures of 1-4 were all determined by single crystal X-ray diffraction studies. These molecules represent the first examples of metal complexes supported by phosphine triphenolate derivatives. The cluster 2 contains a paramagnetic core of high spin Mn(II) (S = 5/2) as indicated by solution and solid state magnetic susceptibility measurements.

Two Comparable Isostructural Microporous Metal–Organic Frameworks: Better Luminescent Sensor and Higher Adsorption Selectivity for the Fluorine‐Decorated Framework

AbstractTwo isostructural 3D metal–organic frameworks (MOFs), {[Zn3(tzba)3(dabco)]·5DMF·3H2O} (1) and {[Zn3(F‐tzba)3(dabco)]·5DMA·3H2O} (2) [tzba = 4‐(1H‐tetrazol‐5‐yl) benzolate, F‐tzba = 2‐fluoro‐4‐(1H‐tetrazol‐5‐yl) benzolate, dabco = triethylenediamine], were solvothermally synthesized from a tetrazolate–carboxylate bifunctional linker and a diamine ligand. The framework contains an uncommon metal–tetrazolate–carboxylate linear trinuclear Zn3(ttaz)3(COO)3 (ttaz = tetrazolyl) cluster, which serves as an eight‐connected node to afford a 3D porous network. Both 1 and 2 show strong photoluminescence and selective luminescent quenching for Cu2+ ions and nitrobenzene relative to that shown by other metal ions (e.g., Na+, K+, Mg2+, Ca2+, Mn2+, Co2+, Ni2+, Cd2+, and Pb2+) and organic solvents (e.g., methanol, ethanol, acetonitrile, n‐propanol, 2‐propanol, ethyl acetate, toluene, dichloromethane, N,N′‐dimethylformamide, and N‐methylpyrrolidone). It is interesting to find that relative to 1, 2 decorated with F atoms exhibits more efficient luminescent sensing for these two guests. Furthermore, 2 also adsorbs more CO2 and has higher CO2/CH4 adsorption selectivities than 1 under the same conditions, which can be ascribed to the CO2‐philic F sites in the pores of 2. These advantages make 2 a promising material in both luminescent sensors and CO2 separation from a CO2/CH4 mixture.

Conversions of zinc cimantrenates in reactions with 1,10-phenanthroline

The reaction between aqueous zinc acetate and cimantrene carboxylic acid has been found to yield Zn[(OOCC5H4)Mn(CO)3] 2[O(H)Me]4, whose dissolution in tetrahydrofuran (THF) gives trinuclear Zn3[μ-(OOCC5H4)Mn(CO)3]4[μ-η2-(OOCC5H4)Mn(CO)3]2(THF)4. Labile THF molecules can be replaced by bidentate 1,10-phenanthroline under mild conditions, thus resulting in Phen2Zn3[μ-(OOCC5H4)Mn(CO)3]4[μ-η2- (OOCC5H4)Mn(CO)3]2. Variations in the reagent ratio and the reaction conditions result in mononuclear PhenZn[(OOCC5H4)Mn(CO)3]2(H2O), which contains a coordinated water molecule. The synthesized complexes have been separated with high yields in the form of single crystals and characterized by chemical analysis, IR spectroscopy, and X-ray diffraction.

Zinc(II) complexes derived from imidazo[1,2-a]pyridin-2-ylacetic acid (HIP-2-ac): [Zn(IP-2-ac)2(H2O)] and unexpectedly, [Zn3(IP-2-ac)6(H2O)]·11H2O

Two zinc(II) complexes based on imidazo[1,2-a]pyridin-2-ylacetate (IP-2-ac), [Zn(IP-2-ac)2(H2O)] (1) and [Zn3(IP-2-ac)6(H2O)]·11H2O (2), were synthesized and characterized by single-crystal X-ray diffraction. In both 1 and 2, zinc(II) ions are five-coordinate with N2O3 donor set, best described as a distorted trigonal-bipyramidal geometry. In 1, two IP-2-ac ligands chelate zinc(II) through a N,O donor set, whereas in 2, both bidentate and μ-bridging binding modes of IP-2-ac are observed. The crystal of 1 comprises discrete Zn(IP-2-ac)2(H2O) coordination entities combined into layers by hydrogen bonds. Inter-layer stabilization of the 3-D crystal lattice is provided by weak C–H⋯O contacts and π⋯π interactions. The structure of 2 consists of discrete trinuclear Zn3(IP-2-ac)6(H2O) coordination entities joined into crystal lattice by multiple water molecules.Compound 1 was characterized by FTIR and FT-Raman spectroscopy, and in terms of thermal stability. Furthermore, its antibacterial activity was tested against selected gram-positive, gram-negative bacteria, and Candida albicans yeast and compared with activity of previously reported [M(IP-2-ac)2(H2O)2]·2H2O (M = Co, Ni, Mn, Cd) complexes.

Synthesis, structure and adsorption of coordination polymers constructed from 3,3′,5,5′-azobenzenetetracarboxylic acid and Zn ions

3,3′,5,5′-Azobenzenetetracarboxylic acid (H4abtc) was synthesized by reduction of 5-nitroisophthalic acid in basic aqueous/ethanol solution in the presence of Zn powder. Three novel coordination polymers {[Zn2(η6-ao2btc)(η2-2,2′-bpy)2(H2O)2]·2H2O}1n (1), {[Zn2(η8-aobtc)(η2-phen)(H2O)]·DMF}3n (2), and {(Hap)2[Zn3(η9-aobtc)2]·2H2O}3n (3) (2,2′-bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, ap = 4-aminopyridine, ao2btc4− and aobtc4− are two oxidized forms of H4abtc ligand) were prepared under hydrothermal conditions. The structures of 1–3 were characterized by single-crystal X-ray diffraction. Complex 1 is a 1D chain polymer, while 2 and 3 are porous 3D metal–organic frameworks with a cavity size of 9 A diameter and 7 × 15 A rectangular cavities, respectively. In 1, ao2btc4− links four mononuclear ZnO6 chromophores. Ligand aobtc4− in 2 links four dinuclear Zn2(CO2)4(H2O)N2, while aobtc4− in 3 bridges four trinuclear Zn3(CO2)8. From a topology point of view, ao2btc4− or aobtc4− are all 4-connected linkers in 1–3, while the mononuclear ZnO6 in 1, dinuclear Zn2(CO2)4(H2O)N2 in 2 and trinuclear Zn3(CO2)8 in 3 are 2, 4 and 8 connected nodes, respectively. Zn(II) in complex 2 can be replaced by Cu(II), Ni(II) and Co(II) with simultaneous loss of crystallinity. The metal ion exchange rate decrease in the order Co(II) < Ni(II) < Cu(II). 2 can encapsulate iodine (I2) in cyclohexane solution to form 2⊃0.1I2. The encapsulated I2 can be released completely in ethanol. The Hap+ in 3 can be replaced by methylene blue in aqueous solution to form 3⊃0.1methylene blue. The insignificant replacement is an indication that the guest molecule in the cavity channel is immobile, which prevents further substitution. With a bis-oxo group in the azo moiety, the framework of 1 is so unstable that it will decompose at ∼150 °C with simultaneous release of NO. Complexes 2 and 3 are stable at 330 °C. IR and fluorescence spectra were also discussed.

Merging catalysis and supramolecular aggregation features of triptycene based Zn(salphen)s

A series of trinuclear, triptycene-based metallosalphen complexes (M = Zn, Ni) have been prepared incorporating various peripheral substituents. The introduction of Zn metal centres into these triptycene based salphen ligands gives rise to cross-linking between different triptycene molecules through μ-phenoxo bridges between the Zn metal centres, and variation in the peripheral groups allows the control of the self-assembling properties as shown by UV-Vis titration data. The strong association of these trinuclear Zn3 complexes under relatively apolar conditions has been exploited to recover the complex after its application as a catalyst in the cycloaddition of carbon dioxide to 1,2-epoxyhexane. The catalysis results and recycling studies show that the co-catalyst structure is important for efficient recovery of the binary system, demonstrating that reversible supramolecular aggregation may become a useful tool for recycling homogeneous catalysts.

Formation of Unusual Trinuclear Assemblies: Scope and Mechanism of Zn(salphen)‐Templated Activation of Pyridine‐Alcohol Substrates (Eur. J. Inorg. Chem. 35/2009)

AbstractThe cover picture shows a schematic view of the templated process that is mediated by Zn(salphen) complexes in the presence of pyridine‐alcohol ligands. The products of the templated reactions are unusual trinuclear Zn3 assemblies that comprise a central, nonsymmetrical Zn complex of which the anionic O‐donor atoms coordinate to two Zn(salphen) units. Full details on the stability and structural features of a small library of these supramolecular systems are discussed in the article by A. W. Kleij et al. on p. 5307 ff.

Graphical Abstract: Eur. J. Inorg. Chem. 35/2009

AbstractThe cover picture shows a schematic view of the templated process that is mediated by Zn(salphen) complexes in the presence of pyridine‐alcohol ligands. The products of the templated reactions are unusual trinuclear Zn3 assemblies that comprise a central, nonsymmetrical Zn complex of which the anionic O‐donor atoms coordinate to two Zn(salphen) units. Full details on the stability and structural features of a small library of these supramolecular systems are discussed in the article by A. W. Kleij et al. on p. 5307 ff.

Synthesis and characterisation of infinite di- and tri-nuclear zinc co-ordination networks with flexible dipyridyl ligands

Crystallisation of flexible dipyridyl ligands with either Zn(NO3)2·6H2O or Zn(ClO4)2·6H2O gave co-ordination networks of composition [Zn3(OH)3{(NC5H4)2C3H6}3][NO3]3·8.67H2O 1 [(NC5H4)2C3H6 = 1,3-bis(4-pyridyl)propane]; [Zn2(OH){(NC5H4)2C4H8}3][ClO4]3·H2O·EtOH 2 [(NC5H4)C4H8 = 1,4-bis(4-pyridyl)butane] and [Zn2(OH){(NC5H4)2C7H14}4][ClO4]3·0.5H2O 3 [(NC5H4)2C7H14 = 1,7-bis(4-pyridyl)heptane]. The compounds were characterised by X-ray single crystal diffraction studies. Compound 1 possesses a trinuclear Zn3(OH)3 6-membered ring that acts as a template for the co-ordination framework. Both 2 and 3 possess dinuclear zinc sub-units (Zn2OH) that contain a bridging hydroxyl ion.