Tetranuclear Zn Research Articles

Experimental and theoretical studies on a salamo-derived biscompartmental ligand and its rare tetranuclear Zn(II) complexes containing solvent effect

Two rare multinuclear zinc(II) complexes: [Zn4(L)2(H2O)2]·4EtOH (1) and [Zn4(L)2(MeOH)2] (2) were self-assembled by the salamo-derived biscompartmental ligand H4L and Zn(NO3)2·6H2O in different mixed solvents. Complex 1 contains two fully deprotonated (L)4− parts, four zinc(II) atoms, and two coordinating water molecules. The Zn1 center is located in a slightly distorted triangular bipyramidal N2O3 coordination environment, and Zn2 is in a twisted tetragonal cone geometrical configuration. Complex 2 is composed of two fully deprotonated (L)4− parts, four zinc(II) ions, and two coordinating methanol solvent molecules. The different structures of the obtained complexes may be attributed to the different solvent effects used during the synthesis. Finally, the properties of the ligand H4L and its Zn(II) complexes were investigated, including molecular electrostatic potential surfaces (MEPs), Hirshfeld surfaces and interaction region indicator (IRI) analyses. Through these studies, the reactive active sites were visualised, the intermolecular interactions of the Zn(II) complexes were elucidated, which is consistent with the crystal structures of the Zn(II) complexes obtained . Their fluorescence properties were also explored.

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.

Novel tetranuclear grid-like Zn(II) complexes derived from dihydrazone pyrimidine derivatives as antitumor agents.

Due to the antitumor properties, Zn(II) complexes have attracted more and more attention. Herein, three novel tetranuclear Zn(II) complexes 1-3 based on dihydrazone pyrimidine derivatives H2L1-H2L3 were synthesized and characterized using IR spectroscopy, 1H NMR spectroscopy, single crystal X-ray diffraction analysis, XRD, TG and elemental analysis. Single crystal X-ray diffraction analysis revealed that 1-3 all displayed a [2 × 2] grid-like topology. The stability in solution, lipophilicity, confocal imaging and antitumor activities were investigated. Complexes 1-3 displayed high structural stability, membrane permeability and different lipophilicities. They can target mitochondria due to the cation charge. The MTT assay indicated that all of them exhibited stronger antiproliferative activity than the corresponding derivatives H2L1-H2L3 and the well-known cisplatin against all the selected tumor cells (BGC-823, BEL-7402, MCF-7 and A549), with IC50 values ranging from 2.83 μM to 7.97 μM. AO/EB double staining, flow cytometry and ROS detection suggested that complexes 1 and 2 could induce BGC-823 apoptosis in a dose-dependent manner. UV-Vis spectra, CD spectra, viscosity analysis and molecular docking revealed that complexes 1 and 2 interact with DNA mainly via partial intercalation and groove binding. Tetranuclear [2 × 2] grid-like Zn(II) complexes have the potential to be promising antitumor agents in the future.

Peroxidative Oxidation of Cyclohexane Using 3d Metal Complexes with Hydrazone-Derived Ligands as Catalysts: Exploring (Un)Conventional Conditions

Two tetranuclear and two mononuclear Cu(II) complexes with arylhydrazones of malononitrile derived ligands (compounds 1–2 and 3–4, respectively), one trinuclear Co(II/III) complex with an arylhydrazone of acetoacetanilide (5) and one tetranuclear Zn(II) complex of 3-(2-carboxyphenyl-hydrazone)pentane-2,4-dione (6) were screened as potential catalysts in the peroxidative oxidation of cyclohexane by aqueous H2O2 in acetonitrile. The best results were attained in the presence of pyrazine-2-carboxylic acid (PCA) with 1 (26% yield, TON = 52.0) and with 2 (24%, TON = 48.0) after 4 h at 40 °C. In the presence of complexes 5 and 6, no oxygenated products were detected in the studied conditions. The employment of non-conventional conditions like supercritical carbon dioxide (scCO2) as reaction medium or microwave (MW) irradiation was assessed for complexes 1 and 2. After 6 h in acetonitrile–scCO2, at 50 °C and with HNO3 as promoter, only 17% yield was achieved using 1 as catalyst, and 21% using 2. Total yields of oxygenates up to 14 (with 1) and 13% (2) and TOFs of 56.0 and 52.0 h−1, respectively, were obtained working under MW irradiation at 70 °C and for the much shorter time of 0.5 h.

Synthesis and structural analysis of tetranuclear Zn(II) complex with 2,3-dihydroxybenzaldehyde-aminoguanidine

Here we report a new Schiff base of aminoguanidine and 2,3-dihydroxybenzaldehyde (H2L) and its physicochemical characterization, along with an investigation into its coordination affinities towards zinc. By reacting zinc acetate with the chloride salt of the ligand in the MeCN?H2O solution, yellow single-crystals of tetranuclear, centrosymmetric complex, with the formula [Zn2(?-L)(?-OAc)2]2?2MeCN, were obtained. The complex was characterized by IR spectroscopy, conductometry, elemental analysis, and single-crystal X-ray diffraction analysis. Notably, both nitrogen atoms of the aminoguanidine residue coordinate to the same zinc atom, while both deprotonated phenyl oxygen atoms achieve bridging coordination. Furthermore, two acetate anions bridge adjacent zinc atoms in addition to the Schiff base anion. Meaningful insights into the hierarchy and significance of intermolecular interactions within the crystal structure were gained by estimating the energies using the CrystalExplorer model. The calculations revealed that the crystal structure can be classified as a layer type, with notably stronger interactions occurring along the [001] and [011] directions.

Synthesis, crystal structure and coordination behaviors of two unexpected tetranuclear Zn(II) and Co(II) supramolecular boxes derived from structural variation of coumarin schiff base ligand

Two unexpected tetranuclear supramolecular boxes, [Zn4(L')4(CH3OH)2]·2CH3OH (1) and [Co4(L)2(L')2(CH3OH)2]·acetone (2), with M4(μ3-O)2(μ2-O)4 core were obtained through reacting coumarin Schiff base H2L (H2L = 4-hydroxy-3-((2-hydroxyphenyl-imino)-methyl)-2hchrome-2-one) with Zn(OAc)2·4H2O and Co(OAc)2·4H2O, respectively. Interestingly, the original ligand (H2L) has changed into a new structure (H2L') in the process of forming single crystals. The structures of 1 and 2 were characterized by X-ray single crystal diffraction. 1 and 2 are tetranuclear structures including four metal centers (Zn(II) or Co(II)), four completely deprotonated ligands (four new (L')2- in 1, two original (L)2- and two new (L')2- in 2), two coordinated methanol molecules and several crystalline solvent molecules. Significantly, due to the action of Zn(II) and Co(II), the original Schiff base H2L completely changed from coumarin skeleton to quinoline skeleton to form a new ligand (H2L') in 1, while in 2 half of the ligands H2L involved in coordination changed to H2L' configuration, the other half maintained the original structure. In 1, Zn1 ions are six-coordinate octahedral configuration and Zn2 are five-coordinate distorted square-pyramidal configuration with τ = 0.38. In 2, Co1 are six-coordinate octahedral configuration and Co2 are five-coordinate triangular bipyramidal configuration with τ = 0.66.

Counteranion-driven self-assembly of di- and tetra-nuclear Zn(II) single‐armed salamo‐type complexes

Di- and tetra-nuclear Zn(II) complexes, [Zn2(L)(µ-OAc)(CH3OH)]·CH3OH (1) and [Zn4(L)2(OMe)2]·2CH3COCH3·CH3OH (2) have been successfully self-assembled by the reaction of a single‐armed salamo‐type ligand (H3L), Zn(OAc)2·2H2O and Zn(NO3)2·6H2O, respectively. In the ligand H3L, tetradentate N2O2 donor part of pocket I and NO2 donor part of pocket II are designed to bond Zn(II) atoms, then unusually structural complexes were obtained by counteranion-driven self-assembled. Both complexes 1 and 2 are characterized by elemental analyses, IR spectra, UV-Vis spectra and single crystal X-ray diffraction. All of the Zn(II) atoms in complexes 1 and 2 are penta-coordinated, but highly distinct configurations are obtained because of the introduction of two kinds of counter-anions. In complex 1, μ-OAc− counter-anion connects the two Zn(II) atoms in one ligand. In complex 2, μ-OMe− counter-anions link the Zn(II) atoms within two ligand molecules and the structure of complex 2 is more complicated. What's more, in complex 1, all Zn(II) atoms have the geometries of distorted trigonal bipyramid, while in complex 2, all Zn(II) atoms have the geometries of distorted square pyramid. There are obvious π···π stacking interactions existing in complexes 1 and 2, which are quantitatively valued by Hirshfeld surfaces analyses. Fluorescence properties are also investigated.

Tetranuclear Zn(II) complexes with ditopic picolinohydrazone ligands: Synthesis, crystal structure, spectroscopic studies, and Hirschfeld surface analysis

Two N- and O-donor hydrazone ligands, (E)-N'-(1-(4‑hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)ethylidene)picolinohydrazide (H2L1) and (E)-N'-(4-oxo-4-phenylbutan-2-ylidene)picolinohydrazide (H2L2), were synthesized by the reaction of picolinohydrazide and dehydroacetic acid or benzolyacetone in methanol solvent. The ligands were characterized by spectroscopic methods and were employed in preparing Zn(II) complexes. Two new tetranuclear Zn(II) complexes, [Zn4(L)2(µ-OAc)4(CH3OH)2] (1) and [Zn4(L2)2(µ-OAc)4(CH3OH)2] (2), were synthesized by the reaction of Zn(OAc)2·H2O with H2L1 and H2L2 in methanol, respectively. These complexes were also characterized by elemental analysis, spectroscopic methods, and single crystal X-ray analysis. Structural studies indicated both 1 and 2 are acetato-bridged tetranuclear Zn(II) complexes and in both of them, the picolinohydrazone ligands are coordinated to the metal ions as both bridging and chelating ligand to fill the coordination environments of Zn(II) ions. In compound 1 four Zn(II) ions have an almost linear arrangement, while in compound 2 they show square arrangement. This matter can be attributed to the steric and electronic difference of the beta-diketone moiety in the structure of ligand. Intermolecular interactions in compounds 1 and 2 were investigated by Hirschfeld surface analysis.

Schiff base tetranuclear Zn2Ln2 single-molecule magnets bridged by hydroxamic acid in association with near-infrared luminescence.

A series of Zn-Ln heteronuclear SMMs constructed by using a hexadentate compartment Schiff base Zn-precursor and lanthanoid ions were structurally and magnetically characterized, in which the two [Zn-Ln] moieties are bridged by a series of hydroxamic acids, resulting in double-decker tetranuclear complexes with the molecular formulae [ZnL1Ln(C2H5O)(qua)]2(CF3SO3)2·2C2H5OH ((1) Ln = Dy; (7) Ln = Yb), [ZnL1Ln(CH3O)(bnz)]2(CF3SO3)2·2CH3OH ((2) Ln = Dy), [ZnL1Ln(CH3O)(aca)]2(CF3SO3)2·2CH3OH ((3) Ln = Dy; (8) Ln = Yb), [ZnL2Dy(CH3O)(bnz)]2(CF3SO3)2·2CH3OH (4), [ZnL2Dy(CH3O)(aca)]2(CF3SO3)2·2CH3OH (5), and [ZnL3Dy(CH3O)(bnz)]2(CF3SO3)2·2CH3OH (6) (HL1 = N,N'-bis(2-hydroxy-3-methoxybenzylidene)-1,2-phenylenediamine, HL2 = N,N'-bis(2-hydroxy-3-methoxybenzylidene)-propane-1,2-diamine, HL3 = N,N'-bis(3-methoxysalicylidene)-1,3-propanediamine, qua = 2-quinolinecarboxylic acid, bnz = benzhydroxamic acid and aca = acetohydroxamic acid). Strikingly, the slow magnetic relaxation can be tuned by modifying the steric hindrance and/or electronic effect on the backbone of the Shiff base and the terminal substituents of hydroxamic acid, as well the magneto-structural correlations are studied. Furthermore, Yb congeners 7 and 8 were synthesized to explore dual-functional materials with both magnetic and fluorescence properties, and they displayed both slow magnetic relaxation and near-infrared (NIR) properties; the low temperature NIR spectroscopic data were correlated with the corresponding slow magnetic relaxation mechanism involving thermally activated ground states to the excited state.

Immobilization of a Zn4 complex on functionalized layered HUS-7: synthesis, structural investigation and catalytic activity

A tetranuclear Zn complex was immobilized into functionalized HUS-7, which showed excellent catalytic performance in two different epoxide ring opening reactions.

Tetranuclear Zn complex covalently immobilized on sulfopropylsilylated mesoporous silica: An efficient catalyst for ring opening reaction of epoxide with amine

Tetranuclear Zn complex, [Zn4(L)2(LH)2((CH3)2SO)2]·2CH3OH·(CH3)2SO·H2O (1) [where LH3 = 3-(E)-(2-hydroxyphenylimino)methyl-4-hydroxy-5-hydroxymethylphenyl (LH3)] was prepared and characterized by single-crystal X-ray analysis. Then, it was incorporated to the sulfopropylsilylated MCM-48, MCM-41 and SBA-15 mesoporous silica materials. The prepared materials were thoroughly characterized by XRD, FT-IR, N2 adsorption/desorption analysis, NH3-TPD, TGA, SEM-EDX and ICP-OES measurements. These catalysts were successfully used for the ring opening reaction of propylene oxide with morpholine producing the corresponding β-aminoalcohols. An abrupt increase in catalytic activities was observed after anchoring of the tetranuclear Zn complex onto the inner surface of sulfopropylsilylated mesoporous materials. Among all the catalysts, the tetranuclear Zn complex incorporated MCM-48 was found to be most active in this reaction system and gave maximum 95% conversion. Catalysis by the tetranuclear Zn complex immobilized on MCM-48 was totally heterogeneous and the catalyst was recyclable up to 4 times without leaching.

Anion-tuned assembly of three double cubane tetranuclear Cd(II)/Zn(II) complexes based on a 2-substituted 8-hydroxyquinoline ligand: Synthesis, crystal structures and fluorescent properties

One unique 2-substituted-8-hydroxyquinoline ligand with 2,3-dimethoxyphenyl groups was synthesized and characterized by ESI-MS, NMR spectroscopy and elemental analysis (EA). Two double cubane tetranuclear Cd(II) complexes [Cd4(L)6(CH3COO)2] (1), [Cd4(L)6(I)2] (2) and one double cubane tetranuclear Zn(II) complex [Zn4(L)6(NO3)2] (3), were prepared by solvothermal reactions of Cd(CH3COO)2, CdI2 and Zn(NO3)2. Complexes 1–3 were characterized with single crystal X-ray diffractions, powder X-ray diffractions (PXRD), thermogravimetry analyses (TGA) and EA. The building blocks exhibited unprecedented structural diversification and their self-assembly afforded tetranuclear Cd(II)/Zn(II) structures binding of different anions and solvent systems. Complexes 1–3 featured three types of supramolecular network controlled by non-covalent interactions, such as C–H⋯O, C–H···π, π···π stacking, hydrogen-bonding, and halogen-related interactions. Investigation of their photoluminescence properties exhibited disparate emission wavelengths and lifetimes in the solid state. This unique capability may provide a useful strategy to tune the optical properties of multinuclear materials, which could be exploited as important components for optoelectronic devices.

Binuclear and tetranuclear Zn(ii) complexes with thiosemicarbazones: synthesis, X-ray crystal structures, ATP-sensing, DNA-binding, phosphatase activity and theoretical calculations.

Two Zinc(ii) complexes [Zn4(L1)4]·2H2O (1) and [Zn2(L2)2]·2H2O (2) of pyruvaldehydethiosemicarbazone ligands are reported. The complexes were characterized by elemental analysis, IR, NMR, UV-vis spectroscopy and by single-crystal X-ray crystallography. X-ray crystal structure determinations of the complexes show that though Zn : ligand stoichiometry is 1 : 1 in both the complexes, the molecular unit is tetranuclear for 1 and binuclear for 2. Both the complexes show selective sensing of ATP at pH 7.4 (0.01 M HEPES) in CH3CN–H2O (9 : 1) medium in the presence of other anions like AcO−, NO3−, F−, Cl−, H2PO4−, HPO42− and P2O72−. The UV-titration experiments of complexes 1 and 2 with ATP results in binding constants of 2.0(±0.07) × 104 M−1 and 7.1(±0.05) × 103 M−1 respectively. The calculated detection limits of 6.7 μM and 1.7 μM for 1 and 2 respectively suggest that the complexes are sensitive detectors of ATP. High selectivity of the complexes is confirmed by the addition of ATP in presence of an excess of other anions. DFT studies confirm that the ATP complexes are more favorable than those with the other inorganic phosphate anions, in agreement with the experimental results. Phosphatase like activity of both complexes is investigated spectrophotometrically using 4-nitrophenylphosphate (NPP) as a substrate, indicating the complexes possess significant phosphate ester hydrolytic efficiency. The kinetics for the hydrolysis of the substrate NPP was studied by the initial rate method at 25 °C. Michaelis–Menten derived kinetic parameters indicate that rate of hydrolysis of the P–O bond by complex 1 is much greater than that of complex 2, the kcat values being 212(±5) and 38(±2) h−1 respectively. The DNA binding studies of the complexes were investigated using electronic absorption spectroscopy and fluorescence quenching. The absorption spectral titrations of the complexes with DNA indicate that the CT-DNA binding affinity (Kb) of complex 1 (2.10(±0.07) × 106 M−1) is slightly greater than that of 2 (1.11(±0.04) × 106 M−1). From fluorescence spectra the apparent binding constant (Kapp) values were calculated and they are found to be 5.41(±0.01) × 105 M−1 for 1 and 3.93(±0.02) × 105 M−1 for 2. The molecular dynamics simulation demonstrates that the Zn(ii) complex 1 is a good intercalator of DNA.

Crystal structure and anti-liver cancer activity of a new tetranuclear Zn complex with 2-ethoxy-6-methyliminomethyl-phenol

A new metal coordination complex [Zn(L)(N3)]4 (1) based on the Schiff base ligand 2-ethoxy-6-methyliminomethyl-phenol (HL) is successfully prepared via a slow evaporation method. The as-prepared metal complex is characterized by various physicochemical techniques, e.g. elemental analysis and X-ray single crystal diffraction. Furthermore, we use a mechanical grinding method to prepare nanosized crystalline complex 1 (nano-1). The anti-liver cancer activity of nano-1 is evaluated in vitro. Firstly, the cell viability and cell proliferation ability are assessed with CCK-8 and cell colony formation assay, respectively. In addition to this, the cell migration and invasion are also evaluated with the transwell assay after indicated treatment.

Molecular di- and tetra-nuclear zinc(II) phosphates with sterically hindered aryl phosphate mono esters ligands

Neutral dinuclear Zn(II) phosphates [Zn2(L)2(phen)2(H2O)2], (L = L2; (1)), anionic dinuclear Zn(II)-phosphates [Et3NH]+[Zn2(L1)4(pyz)2]− (2) and tetranuclear double-4-ring (D4R) Zn(II) phosphates [Zn4(L)4(DMF)4] (5–7), (L = L1; (3), L3; (4), L4; (5)), [Zn4(L1)4(pyz)2(DMF)2] (6) and [Zn4(L4)4(phen)2(DMF)2] (7) were synthesized by using the bulky aryl phosphate ligands (L = 2,6-(diphenylmethyl)-4-alkyl-phenyl substituted phosphates, ArOP(O)(OH)2 (Ar = 2,6-CHPh2-4-R-C6H2; R = Me (L1), Et (L2), i-Pr (L3), and t-Bu (L4)). The preparation of the complexes 1–7 was accomplished at room temperature by the use of additional co-ligands such as phenanthroline or pyrazole. Use of the linear co-ligand, 4,4′-bipyridine, affords the one-dimensional coordination polymer [Zn4(L3)4(bpy)(DMF)2]n, 8 which is built by the fusion of tetranuclear Zn(II) motifs. All the compounds were characterized by single crystal X-ray diffraction techniques.

Dicyanamide-interlaced assembly of Zn(II)-schiff-base complexes derived from salicylaldimino type compartmental ligands: Syntheses, crystal structures, FMO, ESP, TD-DFT, fluorescence lifetime, in vitro antibacterial and anti-biofilm properties

Two new dicyanamide-interlaced tetranuclear Zn(II)-Schiff-base complexes [Zn2(LOMe)(µ-dca-κN1κN5)(µ-dca-κN1)]2(1) and [Zn2(LOEt)(µ-dca-κN1κN5)(µ-dca-κN1)]2(2) were synthesized by using salicylaldimino type Schiff bases (H2LOMe) and (H2LOEt) respectively. Schiff base ligands and the complexes were characterized by elemental analyses, powder X-ray diffraction, FT-IR, FT-Raman, 1H NMR, 13C NMR, UV–Vis, TGA and fluorescence spectroscopy. Dicyanamide modulated complexes were structurally characterized by single crystal X-ray diffraction studies. X-ray crystal structure divulges that the two complexes are isostructural. In both the complexes, the Zn1 metal centers fulfill 5-coordinated distorted square pyramidal geometry having ZnN3O2 chromospheres where Schiff bases are mainly trapped in their complete deprotonated dianionic forms[L]2−, whereas Zn2 metal center attained distorted octahedral geometry. In both complexes two asymmetric units are connected by double μ1,5-dicyanamide ion thus forming Zn4-nuclear metal complex. B3LYP/def2-TZVP level of theory (DFT) successfully applied in both complexes. The complexes (1–2) exhibit intraligand (π → π*) fluorescence in DMSO solvent with lifetimes in the range 0.66–0.82 ns. In vitro antibacterial, membrane damage assay and anti-biofilm properties of both complexes are evaluated against some important Gram-positive and Gram-negative bacterial strains. Finally, the UV–Vis experimental spectral findings are well rationalized with the electronic distribution of HOMO-LUMO through TD-DFT level of calculations.

Effect of the change of the ancillary carboxylate bridging ligand on the SMM and luminescence properties of a series of carboxylate-diphenoxido triply bridged dinuclear ZnLn and tetranuclear Zn2Ln2 complexes (Ln = Dy, Er).

Eleven new dinuclear and tetranuclear compounds of general formulae [Zn(μ-L)(μ-X)Ln(NO3)2]·nS, [Zn2Dy2(μ3-L')2(μ-sal)2(NO3)(CH3OH)](NO3)·5CH3OH and [Zn2Er2(μ3-L')2(μ-sal)2(CH3OH)2](NO3)2·4CH3OH (X = benzoate, anthracenate, diclofenac, salicylate, 2,6-dihydroxybenzoate; Ln = Dy, Er; S = water, acetonitrile, methanol) were prepared from the N,N'-dimethyl-N,N'-bis(2-hydroxy-3-formyl-5-bromobenzyl)ethylenediamine compartmental ligand (H2L). Complexes 1-6 and 9-11 consist of diphenoxido-carboxylate triply bridged compounds, which differ mainly in the carboxylate bridging ligand. It should be noted that the acidic character of the salicylic acid promotes, in the presence of methanol, the methoxylation of the H2L ligand thereby yielding a hemiacetal H3L', which is able to connect the Ln(iii) ions of two ZnLn dinuclear units forming the Zn2Ln2 tetranuclear complexes 7 and 8. All compounds display SMM behaviour in the presence of an external field with effective energy barriers (Ueff) as high as 61 K. Magneto-structural data for these complexes reveal that their SMM behaviour is not only significantly affected by the type of Ln(iii) ion but also by the carboxylate bridging ligand connecting the Zn(ii) and Ln(iii) ions. Photoluminescence properties have also been accomplished, showing that the ligands are able to sensitize lanthanide centred emissions in the visible and near-infrared regions with variable capacity. Moreover, the analysis of the luminescence decay curves reveals emission lifetimes in the range of few microsecond or hundreds of nanoseconds for Dy(iii)-based or Er(iii)-based luminophores, respectively.

New mixed-ligand Ni(II) and Zn(II) macrocyclic complexes with bridged (endo,endo)-bicyclo [2.2.1]hept-5-ene-2,3-dicarboxylate: Synthesis, characterization, antimicrobial and cytotoxic activity

New carboxylate complexes of the tetraazamacrocyclic ligand N,N',N'',N'''-tetrakis(2-pyridilmethyl)-1,4,8,11-tetraazacyclotetradecane (tpmc) with Ni(II) and Zn(II) as central ions were prepared. In mixed-ligand complexes (endo,endo)-bicyclo?2.2.1?hept-5-ene-2,3-dicarboxylate dianion (C9H8O4 2-) is also coordinated to metal ions. The complexes were characterized by elemental analysis (C, H, N), FTIR and UV?Vis spectroscopy, molar conductivity determination and magnetic susceptibility measurement at room temperature. The analytical data of the complexes show the formation of binuclear [Ni2(C9H8O4)tpmc](ClO4)2?4H2O and tetranuclear [Zn4(C9H8O4)(tpmc)2](ClO4)6? ?CH3CN?KClO4?4H2O complexes. In tetranuclear Zn(II) complex bicyclic dicarboxylate ligand is most likely to be bridge coordinated, and in binuclear Ni(II) complex it is coordinated in a combined bridged manner with chelate rings formation. In both complexes macrocyclic ligand was exo coordinated, out of cyclam ring and adopts a boat conformation. The Zn(II) complex is one of the rare tetranuclear Zn(II)-tpmc complexes with carboxylate ion bridging two Zn2tpmc units. The complexes were tested for antibacterial activity against Gram-positive bacteria Staphylococcus aureus (ATCC 25923) and Bacillus subtilis (ATCC 6633), Gram-negative bacterium Escherichia coli (ATCC 25922), and yeast Candida albicans (ATCC 10231), and were screened for antiproliferative activity against human cervix adenocarcinoma (HeLa) and human myelogenous leukemia (K562) cell lines.

A macrocyclic tetranuclear ZnII complex as a receptor for selective dual fluorescence sensing of F− and AcO−: effect of a macrocyclic ligand

Fluorimetric detection of F−/AcO− with an additional ‘INHIBIT’ logic gate response for F−/H+ and AcO−/H+ in an aqueous-methanol medium by a 48-membered macrocyclic ZnII-complex DAS has been explored by combined experimental and theoretical study.

Synthesis of Multinuclear Zn(II) Complexes Involving 8‐Aminoquinoline‐ Based Schiff‐Base Ligand: Structural Diversity, DNA Binding Studies and Theoretical Calculations.

AbstractFour novel Zn(II) complexes [Zn2L2X2] (1), [Zn4L4X(OH)(OH2)][ZnX4]⋅H2O⋅CH3OH (2,3) and [Zn4L4X(OH)(OH2)](N(CN)2)(NO3)⋅ 2H2O⋅CH3OH (4) [where HL=(E)‐2‐methoxy‐6‐((quinolin‐8‐ylimino)methyl)phenol and X= N3−, SCN−, SeCN−, N(CN)2− for 1–4 respectively] were synthesized and characterized by elemental analysis and different spectroscopic techniques viz. IR spectroscopy, UV‐vis spectroscopy and X‐ray crystallography. Complex 1 is hetero (μ‐azido and μ‐phenoxo) bridged dinuclear Zn(II) complex whereas complexes 2, 3 and 4 are tetranuclear Zn(II) complexes with corner‐defective cubane structure. Complexes 2–4 bare the rare examples of presence of three different binding modes (mono, di and triply (μ3) bridging) of phenoxo group of a Schiff base ligand in a single platform. All four complexes exhibit groove binding as well as weak electrostatic interaction with CT‐DNA (calf thymus‐DNA). DFT (density functional theory) and MEP (Molecular electrostatic potential) analysis are also studied for complexes 1–4.