Chemical and electrochemical syntheses of the binuclear zinc and cadmium chelates based on the sterically hindered Schiff bases

Chemical and electrochemical syntheses of a series of the zinc(II) and cadmium(II) complexes were carried out on the basis of sterically hindered Schiff bases, which are the condensation products of 4,6-di-tert-butyl-2-aminophenol with the salicylaldehyde derivatives (H₂L, H₂L¹). The structures and compositions of the synthesized binuclear complexes M₂L₂ and M₂L ₂ ¹ where M = Zn(II) and Cd(II), were proved by the data of elemental analysis, IR spectroscopy, and ¹H NMR spectroscopy. The structures of the Zn₂L₂ · 2Py and Zn₂L₂ · 2DMF dimers were proved by X-ray diffraction analysis. The electrochemical dissolution of zero-valence zinc and cadmium in methanol in the presence of equimolar amounts of H₂L and H₂L¹ made it possible to isolate dimeric complexes of the corresponding metals of the composition M₂L₂ and M_{2 2} ¹ .     

Zinc(II) and cadmium(II) <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>'-Bis(2-<Emphasis Type="Italic">N</Emphasis>-Tosylaminobenzylidene) diaminodipropyliminates: Syntheses,structures, and photoluminescence properties

Chemical and electrochemical syntheses of the zinc(II) and cadmium(II) complexes with the tetradentate Schiff base (H₂L), the condensation product of 2-N-tosylaminobenzaldehyde with diaminodipropylamine, are carried out. The structures, compositions, and properties of the synthesized metal complexes are studied by elemental analyses, IR spectroscopy, ¹H NMR, UV spectroscopy, X-ray absorption spectroscopy, and quantum-chemical calculations. The structure of the cadmium(II) complex is determined by X-ray diffraction analysis (CIF file CCDC no. 1446393). The cadmium(II) and zinc(II) complexes exhibit luminescence in a CH₂Cl₂ solution in the blue spectral range (λ_PL = 425–428 nm) with the photoluminescence quantum yields ? = 0.20 and 0.75, respectively.     

Copper(II) complexes based on 2-thenoyltrifluoroacetone aroyl hydrazones: Synthesis,spectroscopy, and X-ray diffraction analysis

Copper(II) complexes CuL ? NH₃ are synthesized by the interaction of ethanol solutions of parasubstituted 2-thenoyltrifluoroacetylmethane aroyl hydrazones (H₂L¹–H₂L⁴) and an aqueous-ammonia solution of copper(II) acetate in an equimolar ratio. The copper(II) complexes are studied by elemental analysis, IR spectroscopy, and EPR spectroscopy. Single crystals of CuL³ ? NH₃ are grown from 1-(2-thenoyl)- 3,3,3-trifluoroacetone para-methylbenzoyl hydrazone and studied using X-ray diffraction analysis (CIF file CCDC 1045841).     

Electrochemical and chemical syntheses,structures, and optical properties of the zinc and cadmium complexes in the N,N,O,S-ligand environment

The chemical and electrochemical syntheses of the zinc (I) and cadmium (II) complexes are carried out on the basis of the tridentate Schiff base (H₂L), the condensation product of (2-tosylaminoaniline) N-(2-aminophenyl)-4-methylbenzenesulfunamide with 1-phenyl-3-methyl-4-formylpyrazole-5-thiol. The structures and compositions of the synthesized metallochelates are proved by the data of C, H, and N elemental analyses, IR spectroscopy, and ¹H NMR spectroscopy. X-ray absorption spectroscopy is used to determine the structure of the zinc complex. The binuclear structure of the cadmium complex is confirmed by the X-ray diffraction data (CIF file CCDC no. 1471159). The optical properties of H₂L and the zinc and cadmium complexes in dimethyl sulfoxide (DMSO) solutions are studied.     

Electrochemical synthesis and structure of 2-amino-1-ethylbenzimidazole adducts of copper,cobalt, and zinc chelates in the N,N,S ligand environment

2-Amino-1-ethylbenzimidazole (L¹) adducts with copper(II), cobalt(II), and zinc(II) chelates of N,N,S tridentate tosylamino-functionalized mercaptopyrazole-containing Schiff base (H₂L), resulting from condensation of 2-tosylaminoaniline with 1-phenyl-3-methyl-4-formylpyrazole-5-thiol, with the general formula [ML · L¹] were obtained by electrochemical method. The structure and composition of the complexes were confirmed by the data of C, H, N elemental analysis, IR and ¹H NMR spectroscopy, and magnetochemical and X-ray spectral measurements. The mononuclear structure of the copper(II) adduct with coordination bond located on the pyridine type endocyclic nitrogen atom of 2-amino-1-ethylbenzimidazole was proved by X-ray diffraction.     

Synthesis and complexation of two new phenylaminoglyoxime ligands

Two new soluble phenylaminoglyoxime ligands, 4-isopropylanilinephenylglyoxime (L¹H₂), 4-benzylpiperidinephenylglyoxime (L²H₂), were prepared by reacting 4-isopropylaniline and 4-benzylpiperidine with chlorophenylglyoxime. Mononuclear nickel(II), cobalt(II), copper(II), zinc(II), and cadmium(II) complexes with these ligands were synthesized. On the basis of the magnetic and spectral evidence a square-planar geometry for Ni(II) and Cu(II) complexes, a tedrahedral geometry for Cd(II) and Zn(II) complexes and octahedral geometry for Co(II) complexes are proposed. These compounds were elucidated by elemental analysis, IR, UV-Vis, and magnetic moments. The ligands were additionally characterized by ¹H NMR and ¹³C NMR spectra.     

Synthesis,structure, and photoluminescence properties of <Emphasis Type="Italic">N</Emphasis>-{2-[5-(2-hydroxyphenylmethyleneamino)-1-alkylbenzimidazol-2-yl]phenyl}-4-methylbenzenesulfamides and their zinc complexes

N-{2-[5-(2-Hydroxyphenylmethyleneamino)-1-alkylbenzimidazol-2-yl]phenyl}-4-methyl-benzenesulfamides (H₂L) and their zinc complexes Zn₂L₂ were synthesized. The structure of the ligands and complexes was studied by IR, UV, ¹Н NMR, X-ray absorption spectroscopy, and X-ray diffraction analysis. The complexes show green photoluminescence (λ_fl = 492 nm) with quantum yields φ = 0.07–0.17.     

Synthesis,structures, and urease inhibition of nickel(II), zinc(II), and cobalt(II) complexes with similar hydroxy-rich Schiff bases

Four new nickel(II), zinc(II), and cobalt(II) complexes, [Zn(L¹)₂]?·?H₂O (1), [Ni(L¹)₂]?·?H₂O (2), [Ni(L²)₂] (3), and [Co(L³)₂]?·?H₂O (4), derived from hydroxy-rich Schiff bases 2-{[1-(5-chloro-2-hydroxyphenyl)methylidene]amino}-2-methylpropane-1,3-diol (HL¹), 2-{[1-(2-hydroxy-3-methoxyphenyl)methylidene]amino}-2-ethylpropane-1,3-diol (HL²), and 2-{[1-(5-bromo-2-hydroxyphenyl)methylidene]amino}-2-methylpropane-1,3-diol (HL³) have been synthesized and characterized by elemental analyses, infrared spectroscopy, and single-crystal X-ray determination. Each metal in the complexes is six-coordinate in a distorted octahedral coordination. The Schiff bases coordinate to the metal atoms through the imino N, phenolate O, and one hydroxyl O. In the crystal structures of HL¹ and the complexes, molecules are linked through intermolecular O–H···O hydrogen bonds, forming 1-D chains. The urease inhibitory activities of the compounds were evaluated and molecular docking study of the compounds with the Helicobacter pylori urease was performed.     

Cobalt(II), nickel(II), and copper(II) complexes of 14-membered hexaazamacrocycles: synthesis and characterization

Cobalt(II), nickel(II), and copper(II) complexes containing 5,12-di(4-bromophenyl)-7,14-dimethyl-1,2,4,8,9,11-hexaazacyclotetradeca-7,14-diene-3,10-dione (H₂L¹) and 5,12-diphenyl-7,14-dimethyl-1,2,4,8,9,11-hexaazacyclotetradeca-7,14-diene-3,10-dione (H₂L²) have been synthesized. All complexes were characterized by elemental analysis, MALDI TOF-MS spectrometry, and electronic absorption spectroscopy. The crystal structures of two compounds, [Cu₂(H₂L¹)Cl₄]_n and [NiL²], were determined by X-ray powder diffraction. In the polymeric [Cu₂(H₂L¹)Cl₄]_n, the Cu₂Cl₄ units and H₂L¹ molecules are situated on inversion centers. Each Cu(II) has a distorted trigonal-bipyramidal coordination environment formed by N and O from H₂L¹ [Cu–N 2.340(14)?Å, Cu–O 1.952(11)?Å], two bridging chlorides [Cu–Cl 2.332(5), 2.279(5)?Å] and one terminal chloride [Cu–Cl 2.320(6)?Å]. In the [NiL²] complex, the Ni(II) situated on inversion center has a distorted square-planar coordination environment formed by four nitrogens from L² [Ni–N 1.860(11), 1.900(11)?Å].     

Coordination behavior of symmetrical hexadentate O2N2S2-donor Schiff bases toward zinc (II): synthesis,characterization, and crystal structure

Two series of zinc(II) complexes of two Schiff bases (H₂L¹ and H₂L²) formulated as [Zn(HL¹/HL²)]ClO₄ (1a and 1b) and [Zn(L¹/L²)] (2a and 2b), where H₂L¹ = 1,8-bis(salicylideneamino)-3,6-dithiaoctane and H₂L² = 1,9-bis(salicylideneamino)-3,7-dithianonane, have been prepared and isolated in pure form by changing the chemical environment. Elemental, spectral, and other physicochemical results characterize the complexes. A single crystal X-ray diffraction study confirms the structure of [Zn(HL¹)]ClO₄ (1a). In 1a, zinc(II) has a distorted octahedral environment with a ZnO₂N₂S₂ chromophore.     

<Superscript>1</Superscript>H NMR spectra and crystal structure of the nickel(II) complex with ethyl 5,5-dimethyl-2,4-dioxohexanoate aroylhydrazones

Nickel(II) complexes NiL ⁿ ? NH₃ (n = 1–5) with the products of condensation of ethyl 5,5-dimethyl-2,4-dioxohexanoate with aromatic acid hydrazides (H₂L¹–H₂L⁵) were synthesized. The complexes were studied by elemental analysis and IR and ¹H NMR spectroscopy. The structure of the complex NiL₁ ? NH₃ was determined by X-ray diffraction (CIF file CCDC no. 1057268).     

Three new mononuclear group 12 complexes with benzimidazole

Three iso-structural Zn(II), Cd(II), and Hg(II) complexes with 1-benzyl-2-phenyl-1H-benzimidazole (BPB), ZnBPB, CdBPB, and HgBPB, respectively, were synthesized by reaction of the ligand with the corresponding metal chlorides in methanolic solutions. The complexes [MCl₂(BPB)₂], where M?=?Zn(II), Cd(II), or Hg(II), were characterized by elemental analysis, ¹³C, ¹H, and [¹H–¹⁵N] heteronuclear multiple bond coherence NMR measurements, and Raman spectroscopy. The structures of the cadmium and mercury complexes were solved by single-crystal X-ray diffraction, while the structure of the zinc complex was determined by X-ray powder diffraction. The three compounds crystallize in the triclinic system in P-1 space group with the metal ions lying in a distorted tetrahedral environment. The zinc complex shows high luminescence in the solid state at room temperature.     

Synthesis,characterization, and X-ray crystal structures of metal complexes with new Schiff-base ligands and their antibacterial activities

Two new potentially hexadentate Schiff bases, [H₂L¹] and [H₂L²], were prepared by condensation of 2-(3-(2-aminophenoxy)naphthalen-2-yloxy)benzenamine with 3,5-di-tert-butyl-2-hydroxy benzaldehyde and o-vanillin, respectively. Reaction of these ligands with cobalt(II) chloride, copper(II) perchlorate, and zinc(II) nitrate gave complexes ML. The ligands and their complexes have been characterized by a variety of physico-chemical techniques. The solid and solution state investigations show that the complexes are neutral. Molecular structures of [CuL¹], [CoL¹]?·?C₇H₈, and [ZnL²]?·?CH₃CN, which have been determined by single-crystal X-ray diffraction, indicate that [CuL¹] and [ZnL²]?·?CH₃CN display distorted square planar and distorted trigonal-bipyramidal geometry, respectively; the geometry around cobalt in [CoL¹]?·?C₇H₈ is almost exactly between trigonal bipyramidal and square pyramidal. The synthesized ligands and their complexes were screened for their antibacterial activities against eight bacterial strains and the ligands and complexes have antibacterial effects. The most effective ones are [CuL²] against Proteus vulgaris, Serratia marcescens, Staphylococcus subtilis, [H²L¹] against S. subtilis, and [H₂L²] against S. subtilis.     

Coordination chemistry of some new Cu(II), Ni(II) and Co(II) macroacyclic (N2O4) Schiff base complexes: X-ray crystal structure of Cu(II) complex

Six new Cu(II), Ni(II) and Co(II) macroacyclic Schiff base complexes [M^II(H₂L)](ClO₄)₂ (L = L¹ and L²) (I–VI) were prepared by the reaction of two new N₂O₄ Schiff base ligands in equemolar ratios. The ligands H₂L¹ and H₂L² were synthesized by reaction of 2-[2-(2-formyl phenoxy)ethoxy]benzaldehyde (A¹) and/or 2-[2-(3-formylphenoxy)propoxy]benzaldehyde (A²) and ethanol amine and characterized with IR and ¹H, ¹³C NMR spectroscopy. All complexes were characterized by microanalysis, IR and mass spectrometry, whereas complex I was also characterized by single crystal X-ray (CIF file CCDC no. 1020055). The X-ray structure of complex I revealed that all nitrogen and oxygen atoms of ligand (N₂O₄) have coordinated to the metal ion. However, Cu²⁺ ion is in six coordination environment that can bedescribed as a distorted octahedral geometry.     

Synthesis,crystal structure and fluorescence properties of two dinuclear zinc(II) complexes incorporating tridentate (NNO) Schiff bases

Reactions of hydrated zinc(II) trifluoroacetate and sodium azide with two tridentate Schiff bases HL¹ (2-((E)-(2-(dimethylamino)ethylimino)methyl)-4-chlorophenol) and HL² (2-((E)-(2-(dimethylamino)ethylimino)methyl)-4-bromophenol) under the same reaction conditions yielded two dinuclear isostructural zinc(II) complexes, [Zn(L¹)(N₃)]₂ (1) and [Zn(L²)(N₃)]₂ (2), respectively. The complexes were characterized systematically by elemental analysis, UV–Vis, FT-IR, and ¹H NMR spectroscopic methods. Single-crystal X-ray diffraction studies reveal that each of the dinuclear complexes consists of two crystallographically independent zinc(II) ions connected by double bridging phenoxides. All zinc(II) ions in 1 and 2 are surrounded by similar donor sets and display distorted square–pyramidal coordination geometries. The ligands and complexes reveal intraligand ¹(π → π*) flourescence. The enhancement of the fluorescence intensities for the complexes compared to the ligands indicates their potential to serve as photoactive materials.     

Zinc(II) and cadmium(II) complexes with PDT: study of the effect of weak interactions on crystal packing

Two new zinc(II) and cadmium(II) complexes, [Zn(PDT)₂(NCS)₂] (1) and [Cd((PDT)₂I_1.6(H₂O)_0.4(OH)_0.4] · 0.4H₂O (2) (“PDT” is the abbreviation of 3-(2-pyridyl)-5, 6-diphenyl-1,2,4-triazine), have been synthesized and characterized by elemental analysis, IR, ¹H NMR spectroscopy, and studied by X-ray crystallography. Zinc(II) in 1 is six coordinate ZnN₆. 2 is a co-crystal with cadmium(II) being 60% six-coordinated with a CdN₄I₂ environment and 40% seven-coordinated with a CdN₄O₂I environment. The supramolecular features in these complexes are guided/controlled by weak directional intermolecular S ··· π, C–H ··· π, C–H ··· I, and π ··· π interactions.     

Synthesis,structure, and photoluminescence properties of 4-methyl-<Emphasis Type="Italic">N</Emphasis>-{2-([1-alkyl-2-[2-(<Emphasis Type="Italic">p</Emphasis>-tolylsulfonylamino)phenyl]benzimidazol-5-yl]iminomethyl)phenyl}benzenesulfonamides and their zinc complexes

4-Methyl-N-{2-([1-alkyl-2-[2-(p-tolylsulfonylamino)phenyl]benzimidazol-5-yl]iminomethyl)phenyl}-benzenesulfamides (H₂L) and zinc complexes on their basis Zn₂L₂ have been synthesized. The structure of the ligands and complexes has been studied by IR, UV, ¹Н NMR spectroscopy, X-ray absorption spectroscopy, and X-ray diffraction analysis.     

Synthesis,characterization, crystal structures,enzyme inhibition,DNA binding,and electrochemical studies of zinc(II) complexes

Five zinc(II) complexes, [Zn(L¹)₂] (1), [Zn(L¹)₂(phen)H₂O]·H₂O (2), [Zn(L¹)₂(bipy)] (3), [Zn(L²)₂] (4), and [Zn(L²)₂(phen)] (5) (where L¹?=?4-nitrophenylacetate, L²?=?phenylacetate, phen?=?1,10-phenanthroline and bipy?=?2,2′-bipyridine), have been synthesized and characterized by elemental analysis, FT-IR, and multinuclear NMR. Complexes 2, 3, and 4 have been confirmed by single-crystal X-ray diffraction. In 2 and 3, zinc is bonded monodentate to two carboxylates exhibiting distorted trigonal bipyramidal and tetrahedral geometries, respectively, whereas in 4, the carboxylates are bridging bidentate in distorted tetrahedral geometry. The complexes have been screened for electro- and biological activities, including DNA interaction and enzyme inhibition studies. The effect of concentration of 1–5 on the activity of enzyme, alkaline phosphatase, showed that an increase in concentration of complex decreased the activity of the enzyme. Electrochemical behavior of HL¹, 2, and 3 was investigated by cyclic voltammetry and it was observed that ligand-centered electro-activity exhibits a proportionate change on complexation. The UV–visible spectroscopic and viscometric data indicate electrostatic and groove binding of the complexes with DNA. The binding constant and Gibb’s free energy values indicate the feasibility of the complex–DNA interaction and show potent biological activity of the complexes.     

Synthesis,Characterization, DNA Binding Properties,and Antioxidant Activity of Novel Copper(II) and Zinc(II) Complexes with Bis(pyrrol‐2‐yl‐methylamine) Ligands

Three novel ligands H₄Lⁿ (n = 1–3) and their copper(II) and zinc(II) complexes were prepared and characterized on the basis of elemental analyses, molar conductivity, ¹H NMR, UV/Vis, and IR spectroscopy as well as mass spectrometry. DNA binding properties of the ligands and their complexes were investigated by absorption spectroscopy, ethidium bromide displacement experiments, and viscosity measurements. The experimental results indicate that the new ligands and their complexes can bind to DNA and the binding affinities of the complexes are higher than those of the ligands. In addition, the antioxidant activity of the ligands and complexes was determined by superoxide and hydroxyl radical scavenging methods in vitro, indicating that the complexes exhibit more effective antioxidant activity than the ligands alone.     

Synthesis,crystal structures and spectroscopic properties of two Zn(II) Schiff’s base complexes of pyridoxal

Two mononuclear zinc(II) complexes, [ZnL¹H₂Cl]Cl·2H₂O (1·Cl·2H₂O) and [ZnL²HCl]·H₂O (2·H₂O) (L¹H₂ and L²H₂ are N,N′-bis(pyridoxylidene)ethylenediamine and N,N′-bis(pyridoxylidene)1,3-propanediamine, respectively) have been synthesized and characterized by elemental analysis, FT-IR, fluorescence spectroscopy, TG–DTA and single crystal X-ray diffraction studies. The Zn(II) ion in complex 1 have a square pyramidal geometry with appreciable distortion towards trigonal bipyramid, whereas in 2 it has a geometry which is near the midpoint of square pyramid and trigonal bipyramid. The zinc atom is coordinated by two imine nitrogens, two phenolic oxygens and one chloride ion. The Zn(II) complexes show emission at 462 nm when excited at their lowest energy absorption at 372 nm.