Binuclear Zinc Complexes Research Articles

Structural, spectroscopic, fluorescent, and computational studies of binuclear copper (II) and zinc (II) complexes with an asymmetric salamo‐type ligand

Salamo‐type ligand H2L was designed and synthesized and reacted with Cu (II) and Zn (II) acetate, respectively, to obtain two binuclear Cu (II) and Zn (II) complexes: [Cu2(L)2]·2CH3OH (1) and [Zn2(L)2] (2) having the same coordination number but distinct geometries. Complex 1 is a Cu (II) complex containing two crystalline ethanol molecules, where two Cu (II) atoms are surrounded by two utterly deprotonated (L)2− parts, forming slightly twisted tetragonal pyramidal configurations of pentacoordinate. In complex 2, two utterly deprotonated (L)2− parts surround two Zn (II) atoms, forming pentadentate twisted triangular bipyramidal configurations. The complexes were elucidated via IR analyses and ultraviolet spectroscopy. Using DFT theoretical calculation, MEPs, IRI, and Hirshfeld surface analysis to investigate further the molecular interactions and reaction sites. Ultimately, the fluorescence characteristics of H2L and its complexes 1 and 2 were discussed.

Hydrolysis and Transfer Reactivity of the Coordinated Thiolate, Thiocarboxylate, and Selenolate in Binuclear Zinc(II) Complexes.

A new binuclear Zn(II) complex, [Zn2(PhBIMP)(DMF)2]3+ (1) (where PhBIMP1 is the anion of 2,6-bis[bis[(N-1-methyl-4,5-diphenylimidazoylmethyl)amino]methyl]-4-methylphenol), has been shown for the first time to mediate the hydrolytic C-S bond cleavage of a series of aliphatic and aromatic thiolates to yield the corresponding alcohols/phenols along with the formation of a hydrosulfide-bridged complex, [Zn2(PhBIMP)(μ-SH)(DMF)]2+ (2), which has been thoroughly characterized in comparison with the corresponding chloride complex, [Zn2(PhBIMP)(Cl)(DMF)]2+ (3), as a control. The binuclear Zn(II)-thiolate complexes [Zn2(PhBIMP)(μ-SR)]2+ (R = Ph, 4a; 3-Br-C6H4, 4b) have also been synthesized by avoiding the C-S bond cleavage reaction. Based on the experimental results for the effects of H2O and Et3N on 1, 4a, and 4b, the complex [Zn2(PhBIMP)(μ-SR)(OH)]1+ has been proposed to be the active intermediate that precedes the C-S bond cleavage of thiolates. The complex [Zn2(PhBIMP)(μ-SCOPh)(DMF)]2+ (5) also demonstrates the hydrolysis of the coordinated thiobenzoate to produce [Zn2(PhBIMP)(μ-O2CPh)(MeCN)]2+ (6). However, unlike 4a and 5, the benzeneselenolate-bridged complex, [Zn2(PhBIMP)(μ-SePh)]2+ (7), does not generate the species, [Zn2(PhBIMP)(μ-SePh)(OH)]1+, in solution, and in line with that, the coordinated benzeneselenolate in 7 does not undergo hydrolysis to generate hydroselenide and phenol. Finally, a comparative study for the transfer reactivity of the bridging -SH, -SPh, -SC(O)Ph, and -SePh ligands in 2, 4a, 5, and 7, respectively, toward selected organic substrates has been performed to reveal the distinct differences in the reactivity of these bridging ligands.

Synthesis and characterization of novel binuclear zinc complex, immobilization in nano-porous support, and its catalytic application

Binuclear zinc complex, [Zn2(L)(I)2(CH3CN)] (I) (LH2 = 1,2-phenylenebis(azaneylylidene))bis(methaneylylidene))bis(2-methoxyphenol)) was prepared and single-crystal X-ray diffraction was used to establish the structure of complex assembly. Organic acid and base were used to functionalize the nano-porous material and then binuclear Zn complex was grafted into the modified materials. Brunauer-Emmett-Teller isotherm (BET), Nuclear Magnetic Resonance (NMR), Inductively Coupled Plasma analysis (ICP), X-ray Diffraction (XRD), Fourier transform infrared spectra (FT-IR), thermogravimetric analysis (TG), Scanning electron microscope (SEM), etc., were used to characterized the synthesized nano-catalysts to check for existence of guest moiety, structural stability of the parent and modified catalysts. Catalytic performance was noticeably enhanced post modification; without catalyst, acid/base functionalized, Zn2 immobilized catalyst. Binuclear zinc immobilized on acid/base silica catalyst exhibited a maximum 95%, 89% conversion of piperidine, and 87% and 86% conversion of aniline respectively. Prior to the theoretical investigation the bond parameters of the binuclear zinc complex were measured experimentally. Time-dependent Density Functional Theory (TD-DFT) and Density Functional Theory (DFT) methods were used to calculate the molecule's UV–Vis absorption spectra at B3LYP as well as LANL2DZ and 6–31G(d)). LUMOs and HOMOs energy gap were determined from the electronic transitions to determine electrophilicity index (ω), softness (S), electronegativity (χ), hardness value (Ƞ), and chemical potential (μ), etc.

Impact of the zinc complexation of polytopic polyaza ligands on the interaction with double and single stranded DNA/RNA and antimicrobial activity.

Metal complexes have gained a huge interest in the biomedical research in the last decade because of the access to unexplored chemical space with regards to organic molecules and to present additional functionalities to act simultaneously as diagnostic and therapeutic agents. Herein, we evaluated the interaction of two polytopic polyaza ligands and their zinc complexes with DNA and RNA by UV thermal denaturation, fluorescence and circular dichroism spectroscopic assays. The zinc coordination was investigated by X-ray diffraction and afforded the structure of the binuclear zinc complex of PYPOD. Thermal denaturation of DNA and RNA and fluorimetry analysis revealed preferential binding of the zinc-PHENPOD complexes towards GC-containing DNA in contrast to the free ligands. On the other hand, PYPOD metal complexes, compared to the free ligand, stabilized AT-based DNA (B-form) better than AU-RNA (A-form). With regards to single stranded RNA, the binuclear complex of PHENPOD and the free ligand can efficiently identify polyadenylic acid (poly A) among other RNA sequences by circular dichroism spectroscopy. The antimicrobial activity in S. aureus and E. coli bacteria showed the highest activity for the free ligands and their trinuclear zinc complexes. This work can provide valuable insights into the impact of the nuclearity of polytopic polyaza ligands in the binding to DNA/RNA and the antimicrobial effect.

Cooperative effects of Schiff base binuclear zinc complexes on the synthesis of aliphatic and semi-aromatic polyesters.

In this paper, we use mono- and bimetallic complexes based on Earth-abundant, cheap and benign zinc for the synthesis of sustainable aliphatic and semi-aromatic polyesters. Tridentate and hexadentate aldimine-thioetherphenolate ligands were used to obtain the desired zinc complexes by the reaction of proligands with opportune equivalents of zinc bis[bis(trimethylsilyl)amide]. The obtained bimetallic complexes 1 and 2 and the monometallic complex 3 were used as catalysts in the Ring-Opening Polymerization (ROP) of landmark cyclic esters, such as ε-caprolactone and lactide, and in the Ring-Opening COPolymerization (ROCOP) of cyclohexene oxide and phthalic anhydride under different reaction conditions. All catalysts were active in these two classes of reactions, showing good control of the polymerization processes. Interestingly, the bimetallic complexes have higher activity compared to their monometallic counterparts, highlighting the cooperation between the two zinc centers.

A Novel Tri-Coordination Zinc Complex Functionalized Silicotungstate with ROS Catalytic Ability and Anti-Tumor Cells Activity

Reactive oxygen species (ROS) can be used as an effective method to treat tumors. Artificial oxidase has received increasing attention as a catalyst for ROS generation in fields ranging from bioinorganic chemistry to pharmaceutical chemistry. In this study, an artificial oxidase based on a binuclear zinc complex and Keggin-type silicotungstate [Zn2(4,4′-bpy)(Phen)2][SiW12O40] (ZSW) (4,4′-bpy = 4,4′-bipyridine; Phen = 1,10-phenanthroline) was synthesized and structurally featured in terms of its X-ray photoelectron spectrum (XPS), bond valence sum (Σs) calculation, IR spectra, and single-crystal X-ray diffraction (SXRD). ZSW is an ionic compound in which the cation is a binuclear zinc complex [Zn2(4,4′-bpy)(Phen)2]4+ and the anion is a α-Keggin-type silicotungstate [SiW12O40]4– cluster. Notably, the Zn ions in the [Zn2(4,4′-bpy)(Phen)2] exist in tri-coordination, which was first obtained in polyoxometalate (POM) chemistry. It was also demonstrated that ZSW is capable of efficiently catalyzing the production of ROS, which, according to the computational calculations, may be due to the synergistic action of zinc complexes and POM building blocks. Furthermore, ZSW exhibited inhibition ability toward ROS-sensitive tumor cells, such as PC12 cells.

A bowl-shaped phenoxido-bridged binuclear zinc complex: Experimental and theoretical studies

A new dinuclear zinc coordination complex with di(μ-alkoxido) bridge obtained from [[H2L = N,N-(salicyaldene)-1,3-diaminopropan-2-ol] was investigated by IR, 1H- &13C NMR spectroscopy. Single crystal X-ray analysis reveals that the Zn1 atom in the title complex is five coordinated and bound to two alkoxide atoms, two nitrogen atoms, and a chloride ion at apical position in distorted square pyramid geometry, while the second central cation, Zn2, is four coordinated and its O2Cl2 coordination environment is distorted tetrahedral. The single-crystal X-ray crystallographic measurements and DFT calculations reveal that the complex has a bowl-like structure. Hirschfeld surface analysis, energy frameworks QTAIM, NBO, and EDA analyses show clearly that the structure contains a variety of classical and non-classical interactions that help to extend the crystal net dimension. TGA is used to investigate the stability of the structure of the title complex.

Synthesis and Characterization of Novel Binuclear Zinc Complex, Immobilization in Nano-Porous Support, and its Catalytic Application

Synthesis and Characterization of Novel Binuclear Zinc Complex, Immobilization in Nano-Porous Support, and its Catalytic Application

Structural investigations, Hirsfeld surface analyses, and molecular docking studies of a phenoxo-bridged binuclear Zinc(II) complex

A novel phenoxo-bridged zinc complex, [Zn2(L)µ(O-O)2H2OCl2] [L= deprotonated salen ligand, 2,2′-((1E,1′E)-((2,2-dimethylpropane-1,3-diyl)bis(azaneylylidene))bis(methaneylylidene))diphenol), was reported. The title complex was characterized by elemental analyses, single crystal X-ray crystallography, spectroscopic studies, and thermogravimetric analysis. The X-ray structure analysis reveals the coordination of Zn1 atom to two imine nitrogen atoms, two phenolic oxygen atoms, and the oxygen atom of aqua ligand, giving it a distorted square pyramidal geometry, whereas the Zn2 atom is bonded to the same phenoxide anions, and two chloride ions, resulting in a distorted tetrahedral geometry. In addition, TD-DFT and NBO analyses were investigated to obtain bonding information insights into the structure. Furthermore, Hirshfeld surface analysis was used to determine various intermolecular interactions in the complex. Furthermore, a docking analysis was performed on the B-DNA [sequence d (CGCGAATTCGCG)2dodecamer] (PDB ID:1BNA) using the AutoDockvina (scripps) software package. The fluorescence property of the title complex was also carried out, and revealed it to be excellent photoluminescent material.

Highly efficient probe of dinuclear zinc complex for selective detection of oxalic acid

BackgroundOxalic acid (OA) existing widely in animal, plants, and factory processes may affect human health and result in environmental pollution. It is highly desired to develop a rapid fluorescent sensing for accurate determination of OA content in food and wastewater. MethodsWe are the first to design an easy-to-prepare rhodamine-6G based zinc complex as a fluorescent probe for the selective detection of OA and explore the sensing mechanism between zinc complex and OA. The zinc complex presents the coordination with two Zn2+ and both of rapid color and linear fluorescent response toward OA in the range of 0-10 μM. FindingsThe detection limit of the probe for OA can reach to 1.20 μM, which is superior to those reported in the literature. Compared with other dicarboxylic acids, the binuclear zinc complex probe displays rapid detection and high selectivity for OA over a wide pH range due to the steric hindrance and ring strains. The recycling of the probe can be achieved by the treatment with sodium sulfide to form zinc sulfide and regenerate the intermediate.

Synthesis and redox reactions of binuclear zinc(ii)–thiolate complexes with elemental sulfur

The synthesis, characterization and reactivity of a series of binuclear zinc(ii) complexes are described featuring the redox reaction of coordinated thiolates with elemental sulfur.

Electron Microscopic Detection of Single Membrane Proteins by a Specific Chemical Labeling.

SummaryElectron microscopy (EM) is a technology that enables visualization of single proteins at a nanometer resolution. However, current protein analysis by EM mainly relies on immunolabeling with gold-particle-conjugated antibodies, which is compromised by large size of antibody, precluding precise detection of protein location in biological samples. Here, we develop a specific chemical labeling method for EM detection of proteins at single-molecular level. Rational design of α-helical peptide tag and probe structure provided a complementary reaction pair that enabled specific cysteine conjugation of the tag. The developed chemical labeling with gold-nanoparticle-conjugated probe showed significantly higher labeling efficiency and detectability of high-density clusters of tag-fused G protein-coupled receptors in freeze-fracture replicas compared with immunogold labeling. Furthermore, in ultrathin sections, the spatial resolution of the chemical labeling was significantly higher than that of antibody-mediated labeling. These results demonstrate substantial advantages of the chemical labeling approach for single protein visualization by EM.

Binuclear Schiff-base zinc(II) complexes: Synthesis, crystal structures and reactivity toward ring opening polymerization of rac-lactide

Upon crystallization from DMF/diethyl ether or CH2Cl2/pyridine of tetracoordinated Zn(II) complexes containing either 4-fluorophenyl or 4-anisyl substituted O,N,O-tridentate Schiff base ligands and pyridine as auxiliary ligand, three new doubly phenoxide-bridged dimeric Zn(II) complexes were isolated and their catalytic properties for the ring opening polymerization (ROP) of rac-lactide were explored. The single-crystal XRD analysis allowed to corroborate the molecular structures of the binuclear complexes, showing that the pentacoordinated Zn(II) metal ion adopts a slightly distorted square pyramidal geometry. The basal plane Is formed by the O,N,O-donor set of the tridentate Schiff base ligand and a phenoxo bridging oxygen, while a pyridine or a DMF molecule is located at the apex of the pyramid. The binuclear complexes were employed as catalysts in the ROP of rac-lactide for polylactide (PLA) synthesis. Polymerization conditions such as reaction time, catalyst concentration and use of benzyl alcohol as cocatalyst were studied, as well as their influence on the conversion rate, average molecular weight and polydispersity of the obtained PLA. The catalyst substituted with fluorine was more reactive, but with a lower control on the molecular weight compared to the methoxy-substituted catalyst. On the other hand, the presence of pyridine as an auxiliary ligand generates an improvement in the polydispersity of PLA.

Solution and solid behavior of mono and binuclear zinc(ii) and nickel(ii) complexes with dithiocarbazates: X-ray analysis, mass spectrometry and cytotoxicity against cancer cell lines

We report the synthesis and characterization of metal complexes with dithiocarbazates and the cytotoxicity against the breast cancer line MDA-MB-231.

Crystal Structure and Luminescence of a Novel Binuclear Zinc(II) Complex with Di-2-Pyridylamine And 4,4′-Sulfonyldibenzoate

A binuclear Zn(II) complex [Zn2(SDBA)2(DPA)2.2H2O] (1) (DPA = di-2-pyridylamine, H2SDBA = 4,4′- sulfonyldibenzoic acid) is synthesized and characterized using single crystal X-ray diffraction, IR spectroscopy, and elemental analysis. The single crystal X-ray diffraction analysis reveals that complex 1 is a binuclear zinc(II) complex. The binuclear molecules are further connected by three types of N–H...O, C–H...O, and O–H...O hydrogen bonds, generating a three-dimensional supramolecular structure. Meanwhile, S–O...π interactions further consolidate the three-dimensional supramolecular framework of 1. In addition, the thermal stability and luminescent properties of the title complex are briefly investigated. The luminescence measurements reveal that complex 1 exhibits fluorescent emission in the solid state at room temperature.

Polarized Light-Induced Molecular Orientation Control of Rigid Schiff Base Ni(II), Cu(II), and Zn(II) Binuclear Complexes as Polymer Composites

We have investigated linearly polarized UV light-induced molecular orientation due to Weigert effect of composite materials of new six binuclear nickel(II), copper(II), and zinc(II) complexes of two rigid Schiff base ring ligands (L1 and L2) composite materials with methyl orange (MO), an azo-dye, in polyvinylalchol (PVA) cast films. To compare the degree of molecular orientation, two ligands, namely flexible aliphatic cyclohexane (ML1: NiL1, CuL1, ZnL1) and rigid aromatic (ML2: NiL2, CuL2, ZnL2), were synthesized using amine moiety. We have also characterized these complexes by means of elemental analysis, IR, and UV-vis spectra, single crystal or powder X-ray diffraction (XRD) analysis, and so on. Composite materials of ML1 or ML2+MO+PVA were also prepared to separately disperse the solutes in a polymer matrix. For any metal complexes, optical anisotropy (represented as the R parameters) of ML2+MO+PVA was larger than ML1+MO+PVA because of the rigidness of the ligands.

Crystal structure and luminescence of a novel binuclear zinc(II) complex with di-2-pyridylamine and 4, 4'-sulfonyldibenzoate

Crystal structure and luminescence of a novel binuclear zinc(II) complex with di-2-pyridylamine and 4, 4'-sulfonyldibenzoate

Synthesis, Structure and Properties of Binuclear Zinc Complex [Zn(dna)(phen)(H 2 O)

Synthesis, Structure and Properties of Binuclear Zinc Complex [Zn(dna)(phen)(H 2 O)

Binuclear zinc(II) complexes of N(4)-substituted bis(thiosemicarbazone) ligands incorporating hydroxyl group and their non-hydroxyl analogues

We have reported the synthesis and physical and chemical studies of the new zinc complexes of N(4)-substituted bis(thiosemicarbazones). The complexes characterized by spectroscopic methods. The crystal structures of the compounds [Zn2L2(CH3COO)]·EtOH and [Zn2L4(CH3COO)]·MeOH is determined. Bis(thiosemicarbazones) involving a pendant OH group having SNONS donor sequences can hold two metal ions in close proximity. The coordination sphere has been formed by the imine nitrogen and sulfur atom, and the remaining positions, in a square-based pyramid, has been occupied by three oxygen atoms derived of pendant OH, ether group and acetate ligand. Acetate ligand and alkoxide oxygen are bridged between two metal centers. Whereas, their non-hydroxyl analogues are dimer. In dimer complexes, two ligands are tetradentate coordinated via N2S2 donor atoms. The presence of bulky groups on the nitrogens of thiosemicarbazide enforce an s-trans conformation for the H2L1 and H2L3 ligands in [ZnL1]2·MeOH and [ZnL3]2·MeOH. Fluorescence studies suggest that the [ZnL1]2·MeOH complex can be utilized as a fluorescent imaging agent.

Synthesis of ChiralC2-Symmetric Bimetallic Zinc Complexes of Amido-Oxazolinates and Their Application in Copolymerization of CO2and Cyclohexene Oxide

A family of new chiral C2 symmetric amido-oxazolinate ligands H2L (1 a-1 d) that are bridged by three different linkers based on m-phenylenediamine, 4-(4’-aminobenzyl)benzenamine, and 1,8-diaminoanthracene have been synthesized in high yields (85-90 %). Treatment of ligands (1 a-1 d) with two equiv. of Zn[N(SiMe3)2]2 in dry toluene generated a series of heteroleptic dizinc complexes (L)[ZnN(SiMe3)2]2 (2 a-2 d) and reaction of 1 b with one equiv. of Zn[N(SiMe3)2]2 leads to formation of a homoleptic binuclear zinc complex (L)2Zn2 (3 b) in good yield. Complexes 2 a-2 d were found to be effective catalysts for asymmetric alternating copolymerization of CO2 and cyclohexene oxide (CHO). The catalyst 2 a is more active towards polycarbonate formation (78 % carbonate linkages), while the catalyst 2 d generates highly isotactic poly(cyclohexene carbonate) (86 % of m-centered tetrads).