Trinuclear Zinc Research Articles

(10,3)-a Noninterpenetrated Network Built from a Piedfort Ligand Pair

The Friedel-Crafts reaction of cyameluric chloride with toluene and subsequent oxidation have resulted in the synthesis of a benzoic acid functionalized tri-s-triazine derivative, s-heptazine tribenzoate (HTB). Photoluminescence and mass spectroscopy data indicate that, in solution, HTB molecules interact by face-to-face pi-pi stacking, forming dimers (the "Piedfort unit"). A porous metal-organic framework (MOF) with a (10,3)-a chiral network has been synthesized with these dimers at the three-connected nodes linking trinuclear zinc clusters. Within the network, the dimer can exist in either of two enantiomeric forms because of an angular offset in the stacking. The resulting MOF is neutral and noninterpenetrated and exhibits a high solvent-accessible volume (calculated 84%).

A Stable Trinuclear Zinc Cluster Assembled from a Thiazolylazo Dye and Zinc Acetate: Preparation, Structural Characterization and Spectroscopic Studies

AbstractA thiazolylazo dye, 5‐(diethylamino)‐2‐(2‐thiazolylazo)phenol (HL), containing potential tridentate binding sites was synthesized in high yield and well characterized. In solution, the reaction of zinc acetate and the deprotonated ligand, L–, results in the instantaneous formation of the supramolecular trinuclear species [Zn3L2(OAc)4] (1). UV/Vis and 1H NMR spectroscopic titration experiments in solution confirmed that the ligand and zinc salt interact spontaneously with each other and produce exclusively the polymetallic complex with the metal‐to‐ligand ratio of 3:2. The crystal structures of both the ligand and coordination complex are reported in this paper. The aromatic part of HL is planar and, significantly, the intermolecular C–H···π hydrogen bonds and thiazo ring‐S···π weak interactions observed here should be responsible for the orthorhombic space group P212121. The structure of 1 reveals a linear trinuclear zinc cluster. The two L– units are linked to three zinc atoms in an N2O tridentate mode, and the four acetate anions are chelated to three metal centers as bridges to result in two pentacoordinate and one hexacoordinate zinc centers. The resulting bridging Zn1–Zn2–Zn1A array is linear by symmetry, with a nonbonding Zn···Zn distance of 3.390 Å and a Zn1···Zn2···Zn1A angle of 180.0°. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

{Zn3(Et2O)2[(EtO)PO2(C6H5NH)]6·2THF}: A Trinuclear Zinc Amidophosphate with an Hourglass Structure

The reaction of ZnMe2 and the N-substituted phosphoramidic monoester [Et2NH2][(EtO)PO2(C6H5NH)] produces the trinuclear zinc cluster Zn(3)(Et2O)2[(EtO)PO2(C6H5NH)]6.2THF, demonstrating that the P-N bond can survive under mild solvothermal reaction conditions.

Mode of Action of Bi‐ and Trinuclear Zinc Hydrolases and Their Synthetic Analogues

AbstractFor Abstract see ChemInform Abstract in Full Text.

A Highly Efficient Initiator for the Ring-Opening Polymerization of Lactides and ε-Caprolactone: A Kinetic Study

A trinuclear zinc alkoxide [{(BDI-OMe)Zn(μ-OBn)}2Zn(μ-OBn)2] (1) and a homoleptic zinc complex [(BDI-OMe)2Zn] (2) have been prepared by the addition of benzyl alcohol to a mixture of BDI-OMe-H with Et2Zn. Compound 1 has been employed as an initiator for ring-opening polymerization of lactides and e-caprolactone. The highly efficient initiator of the zinc complex shown in the polymerization process enabled us to synthesize the PLA at ambient temperature, yielding PLA with well molecular control and narrow molecular weight distribution in a very short period of time. The polymerization kinetics were studied with [LA]0/[1] = 200/1 and [LA]0 = 0.5 M at 25 °C. Experimental results indicate a second-order dependency on [LA] (kobs = 0.033 M-1 s-1). Moreover, a first-order dependency in [1] is indicated of kobs vs [Initiator], with a slope equal to the first-order rate constant k = 12.2 M-2 s-1. Furthermore, the heterotactic PLA with Pr up to 83% can be achieved in a mixed solvent of CH2Cl2 and THF at −35 °C. How...

Hydrolysis of a mRNA 5′- cap model substrate, 5′,5′-ApppA by di- and trinuclear zinc(II) complexes of a polyamino-polyol ligand

Copper(II) and zinc(II) complexes of a polyamino-polyol ligand 1,3,5-trideoxy-1,3,5-tris(methylamino)- cis-inositol (tmci) have been investigated as potential candidates for the selective elimination of the 5′- cap structure of mRNA. A cap-model compound ApppA has been utilised as substrate for studying the effect of the different metal ion complex catalysts on the hydrolysis of the triphosphate bridge. Kinetic experiments have been performed by the variation of pH, metal-to-ligand ratio and total concentrations of the metal ion and ligand. The zinc(II) complexes of tmci have been proved to possess a remarkable activity for the hydrolysis of ApppA. The observed rate enhancement compared to the uncatalysed reaction was found to be 12,000-fold, in the presence of 4.5 mM zinc(II) and 1.5 mM tmci at pH ∼ 7.5. In contrast with the copper(II) containing systems, an extra product has also been formed during the cleavage process, beside the expected AMP and ADP. According to the ESI-MS characterisation of the samples, the additional product is a covalent phosphoester adduct of AMP and the ligand. The formation of this species is initiated by a nucleophilic attack of a zinc(II)-bound alcohol or alkoxo group on one of the α phosphate groups of ApppA, which leads to the formation of a phosphodiester bond. In an alternative pathway, the substrate is cleaved into AMP and ADP. According to the pH-potentiometric studies, performed with the tmci–zinc(II) system, di- and trinuclear complexes are responsible for the accelerated ApppA hydrolysis. The copper(II)-tmci 2:1 system showed only a modest kinetic activity. The rate acceleration significantly increased when threefold excess of copper(II) was applied. Although, the detailed investigations above pH ∼ 6.6 have been prevented by precipitate formation during the addition of the substrate into the reaction solution, the activity of the copper(II)–tmci 3:1 system does not exceed that of the zinc(II) complexes. Due to the specific mechanism leading to the covalent extra product, the zinc(II) complexes of tmci provide a comparable rate enhancement for ApppA hydrolysis to the widely studied lanthanide or copper(II) species, in spite of the fact that they are stronger Lewis acids.

Structural characterization and photophysical properties of a luminescent trinuclear zinc(II) complex exhibiting multiple coordination geometries

A luminescent trinuclear zinc(II) complex, tris(μ-2,3-toluenedithiolato)-1:2κ2S1;1:2κ2S1′, 2:3κ2S2;3κS2′, 1:3κ2S3;3κS3′-bis(2,2′-bypyridine)-1κ2N,N′,2κ2N,N′-trizinc, containing 3,4-dimercaptotoluene (tdt) and 2,2′-bipyridine (bpy) has been synthesized and found to have the trinuclear formulation Zn3(tdt)3(bpy)2 (I). The complex crystallizes in the monoclinic space group P21/n with a = 11.7247(12), b = 20.134(2), c = 17.7376(18) A and β = 103.743(2)∘. The complex has two heteroleptic zinc(II) centers exhibiting similar distorted trigonal bipyramidal geometries with the third homoleptic zinc(II) center displaying a flattened tetrahedral geometry. Present in the solid state are both intra- and intermolecular π–π interactions. The complex is emissive at 77 K in the solid state with an emission maximum at 574± 2 nm with a luminescence lifetime of 7.4± 0.4 ns. The unstructured emission is assigned as a metal-mediated ligand-to-ligand π–π* charge transfer transition.

Mode of Action of Bi- and Trinuclear Zinc Hydrolases and Their Synthetic Analogues

Mode of Action of Bi- and Trinuclear Zinc Hydrolases and Their Synthetic Analogues

A unique example of a 36 tessellated 2-D net based on a tri-nuclear zinc(ii)-1,4-benzenedicarboxylate framework

Reaction of Zn(NO3)2 and 1,4-benzenedicarboxylic acid (1,4-H2BDC) at 100 degrees C for 24 hours in a pressure tube yielded on cooling {[Zn3(1,4-BDC)3(DEF)2].DEF}(infinity) (DEF = diethylformamide) incorporating planar six-connected centres to give a unique 3(6) tessellated 2-D framework polymer.

Cooperative formation of trinuclear zinc(II) complexes via complexation of a tetradentate oxime chelate ligand, salamo, and zinc(II) acetate.

Novel trinuclear zinc(II) complexes [Zn(3)L(2)(OAc)(2)] (L = salamo, 3-MeOsalamo) were synthesized, and their structures were determined by X-ray crystallography. Ligation of methoxy groups in the salamo ligand causes a significantly different coordination mode of the central zinc atom in the trinuclear system. The complexes between the salamo ligands and zinc(II) in methanol formed exclusively and very cooperatively. In contrast to other imine ligands, the mononuclear [ZnL] and other complexes are not observed at all.

A trinuclear zinc–cerium complex: [CeZn2{CH2C(CH3)COO}6(NO3)(2,2′-bipyridine)2

In the novel title carboxyl­ate-bridged trinuclear zinc–cerium complex, bis(2,2′-bi­pyridine)­hexakis-μ-methacryl­ato-nitrato­cerium(III)­dizinc(II), [Zn2Ce(C4H5O2)6(NO3)(C10H8N2)2], the Ce and each of two Zn atoms are bridged by three bidentate carboxyl­ate groups. The Ce⋯Zn separations are 4.011 (1) and 3.982 (1) Å. The Ce atom is eight-coordinate in irregular polyhedron. Each Zn atom is five-coordinate, with a distorted pyramidal geometry.

Solution-stable trinuclear zinc(ii) cluster from 4-methyl-2-N-(2-pyridylmethylene)aminophenol (HPyrimol)

The reaction of zinc(II) acetate with 4-methyl-2-N-(2-pyridylmethyl)aminophenol (HPyramol) in methanol leads to a solution stable linear trinuclear zinc cluster with intramolecular ligand oxidation.

Multiple bonding modes exhibited by heteroscorpionate N 2S(alkylthiolate) ligands with Zn(II) and Fe(II)

Two related heteroscorpionate N 2S(thiolate) ligands L 1 and L 2 have been employed in the synthesis of new zinc(II) and iron(II) complexes. These ligands contain two imidazolyl donors and one alkylthiolate donor connected by a central carbon atom. The ligand L 1 was reacted with ZnBr 2 to give the trinuclear zinc complex [(L 1) 3Zn 3Br 2]Br ( 1). The X-ray structure of 1 reveals one of the zinc ions to be coordinated by two L 1 ligands in a tripodal arrangement resulting in a distorted octahedral geometry, while the other two zinc ions are both held in a distorted tetrahedral geometry and are coordinated to another molecule of L 1 in an unusual tridentate, multibridging coordination mode. Modification of L 1 to include phenyl substituents on the imidazole groups leads to L 2, and these substituents cause quite a different result to be obtained in the reaction with ZnBr 2. The combination of L 2 and ZnBr 2 leads to the dimeric zinc complex (L 2) 2Zn 2Br 2, ( 2). Characterization of 2 by X-ray diffraction shows this complex to be a dimer with a central Zn 2(μ-SR) 2 rhomb. Each zinc ion is found in a distorted tetrahedral geometry coordinated by L 2 in a bidentate, N,S fashion. The 1H NMR spectrum of 2 provides strong evidence this structure is retained in solution. In comparison, reaction of L 2 with FeCl 2 leads to the monomeric complex (L 2) 2Fe II ( 3), which has each ligand coordinated in the same bidentate, N,S bonding mode. Interestingly, the methoxy groups of the two ligands in 3 are close enough to the iron center for a possible bonding interaction, suggesting an unexpected N 2O coordination mode.

Crystal structure of the Escherichia coli YcdX protein reveals a trinuclear zinc active site.

Crystal structure of the Escherichia coli YcdX protein reveals a trinuclear zinc active site.

New mechanistic insight into the coupling reactions of CO2 and epoxides in the presence of zinc complexes.

Coupling reactions of CO(2) and epoxide to produce cyclic carbonates were performed in the presence of a catalyst [L(2)ZnX(2)] (L=pyridine or substituted pyridine; X=Cl, Br, I), and the effects of pyridine and halide ligands on the catalytic activity were investigated. The catalysts with electron-donating substituents on pyridine ligands exhibit higher activity than those with unsubstituted pyridine ligands. On the other hand, the catalysts with electron-withdrawing substituents at the 2-position of the pyridine ligands show no activity; this demonstrates the importance of the basicity of the pyridine ligands. The catalytic activity of [L(2)ZnX(2)] was found to decrease with increasing electronegativity of the halide ligands. A series of highly active zinc complexes bridged by pyridinium alkoxy ions of the general formula [((mu-OCHRCH(2)L)ZnBr(2))(n)] (n=2 for R=CH(3); n=3 for R=H; L=pyridine or substituted pyridine) were synthesized and characterized by X-ray crystallography. The dinuclear zinc complexes obtained from propylene oxide adopt a square-planar geometry for the Zn(2)O(2) core with two bridging pyridinium propoxy ion ligands. Trinuclear zinc complexes prepared from ethylene oxide adopt a boat geometry for the Zn(3)O(3) core, in which three zinc and three oxygen atoms are arranged in an alternate fashion. These zinc complexes bridged by pyridinium alkoxy ions were also isolated from the coupling reactions of CO(2) and epoxides performed in the presence of [L(2)ZnBr(2)]. Rapid CO(2) insertion into the zincbond;oxygen bond of the zinc complexes bridged by pyridinium alkoxy ions leads to the formation of zinc carbonate species; these which yield cyclic carbonates and zinc complexes bridged by pyridinium alkoxy ions upon interaction with epoxides. The mechanistic pathways for the formation of active species and cyclic carbonates are discussed on the basis of results from structural and spectroscopic analyses.

Novel synthetic approach to trinuclear 3d-4f complexes: specific exchange of the central metal of a trinuclear zinc(II) complex of a tetraoxime ligand with a lanthanide(III) ion.

Only the central metal atom of the homotrinuclear complex [LZn3]2+, prepared by cooperative complexation between a linear ligand and Zn(OAc)2, is replaced with a Ln3+ ion by selective and quantitative transmetalation to give a helical heterotrinuclear complex [LZn2Ln]3+ (see scheme). Ln=lanthanide.

Syntheses and Molecular Structures of Metallasiloxanes Containing Zn3O4 and Zn6Si6O10 Cores

AbstractThe trinuclear zinc siloxane [(MeZn)2Zn(OSiPh3)4] (1) and the first novel siloxane‐bridged hexanuclear dimer [{Me(THF)Zn}2OZn(OSiR2)(R1)]2 (R = Ph, R1 = OSiR2OSiR2O) (2) are accessible by Brønsted acid/base reaction of triorganosilanols with the zinc base ZnMe2. Both compounds were characterised by NMR spectroscopy and a single‐crystal X‐ray structure analysis. The X‐ray structures of the reported complexes are discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Novel Synthetic Approach to Trinuclear 3d‐4f Complexes: Specific Exchange of the Central Metal of a Trinuclear Zinc(II) Complex of a Tetraoxime Ligand with a Lanthanide(III) Ion

Nur das zentrale Metallatom des homodreikernigen Komplexes [LZn3]2+, der durch kooperative Komplexierung aus einem linearen Liganden L und Zn(OAc)2 gewonnen wird, wird durch selektive und quantitative Transmetallierung durch ein Ln3+-Ion ersetzt. Es resultiert ein helicaler heterodreikerniger Komplex [LZn2Ln]3+ (siehe Schema). Ln=Lanthanoid.

The Metal Complex of 2-[2-(4-Cyanophenyl)ethenyl]-8-hydroxyquinoline (2-CEHQ) Ligand: A Novel Trinuclear Zinc(II) Complex with Red Light Emission

Abstract A neutral trinuclear zinc(II) complex containing 2-[2-(4-cyanophenyl)ethenyl]-8-quinolinol (2-CEQH) with strong red light emission was synthesized by hydro(solvo)thermal reaction and its structure was determined by X-ray single crystal diffraction study.

Some DI- and Trinuclear Zinc Complexes: Anion Induced Complex Formation

Complexes of N,N′-bis(salicylidene)-1,3-diaminopropane, an ONNO type ligand, with ZnX2 (X = AcO−, NO3-, Cl−, Br−, I−) salts were prepared. Molecular structures of these complexes were identified using elemental analyses, IR spectrometry and X-ray diffraction techniques. It has been observed that the reactions between zinc ions and the said ligand tend to produce polynuclear complexes and depending on the anion present either di- or trinuclear complexes are formed. Thus, it can be deduced from the results presented in this article that trinuclear complexes form when the zinc salt used was the acetate or nitrate and dinuclear complexes form if the anion in the zinc salt is a halogen.