Co(II), Ni(II), Cu(II) and Zn(II) complexes of aminothiazole‐derived Schiff base ligands: Synthesis,characterization, antibacterial and cytotoxicity evaluation,bovine serum albumin binding and density functional theory studies

Transition metal complexes of type M(L)₂(H₂O)_x were synthesized, where L is deprotonated Schiff base 2,4‐dihalo‐6‐(substituted thiazol‐2‐ylimino)methylphenol derived from the condensation of aminothiazole or its derivatives with 2‐hydroxy‐3‐halobenzaldehyde and M = Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ (x = 0 for Cu²⁺ and Zn²⁺; x = 2 for Co²⁺ and Ni²⁺). The synthesized Schiff bases and their metal complexes were thoroughly characterized using infrared, ¹H NMR, electronic and electron paramagnetic resonance spectroscopies, elemental analysis, molar conductance and magnetic susceptibility measurements, thermogravimetric analysis and scanning electron microscopy. The results reveal that the bidentate ligands form complexes having octahedral geometry around Co²⁺ and Ni²⁺ metal ions while the geometry around Cu²⁺ and Zn²⁺ metal ions is four‐coordinated. The geometries of newly synthesized Schiff bases and their metal complexes were fully optimized in Gaussian 09 using 6–31 + g(d,p) basis set. Fluorescence quenching data reveal that Zn(II) and Cu(II) complexes bind more strongly to bovine serum albumin in comparison to Co(II) and Ni(II) complexes. The ligands and their complexes were evaluated for in vitro antibacterial activity against Escherichia coli ATCC 25922 (Gram negative) and Staphylococcus aureus ATCC 29213 (Gram positive) and cytotoxicity against lever hepatocellular cell line HepG2.     

Syntheses,equilibrium, and structural studies of copper(II) and nickel(II) complexes with a tripodal alanine-based ligand

A heptadentate ligand, tris[(L)-alanyl-2-carboxamidoethyl]amine (H₃trenala), has been synthesized as its tetrahydrochloride salt; its protonation constants and the stability constants of the copper(II) and nickel(II) chelates have been determined by potentiometry. Mononuclear species with protonated, neutral, or deprotonated forms of the ligand, [Cu(H₅trenala)]⁴⁺, [M(H₄trenala)]³⁺, [M(H₃trenala)]²⁺, [M(H₂trenala)]⁺, and [M(Htrenala)] (M?=?Cu²⁺ and Ni²⁺) have been detected in all cases, while only Cu²⁺ gives dinuclear [Cu₂(H₂trenala)]²⁺, [Cu₂(Htrenala)]²⁺, [Cu₂(trenala)]⁺, and [Cu₂(trenala)(OH)] species. Two dinuclear copper(II) complexes have been prepared and characterized by spectroscopic techniques (IR, UV-Vis, mass electro-spray) and thermogravimetric analysis.     

Complexes of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with 4-chloro-2-methoxybenzoic acid anion

The complexes of 4-chloro-2-methoxybenzoic acid anion with Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ were obtained as polycrystalline solids with general formula M(C₈H₆ClO₃)₂·nH₂O and colours typical for M(II) ions (Mn – slightly pink, Co – pink, Ni – slightly green, Cu – turquoise and Zn – white). The results of elemental, thermal and spectral analyses suggest that compounds of Mn(II), Cu(II) and Zn(II) are tetrahydrates whereas those of Co(II) and Ni(II) are pentahydrates. The carboxylate groups in these complexes are monodentate. The hydrates of 4-chloro-2-methoxybenzoates of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) heated in air to 1273 K are dehydrated in one step in the range of 323–411 K and form anhydrous salts which next in the range of 433–1212 K are decomposed to the following oxides: Mn₃O₄, CoO, NiO and ZnO. The final products of decomposition of Cu(II) complex are CuO and Cu. The solubility value in water at 293 K for all complexes is in the order of 10^–3 mol dm^–3. The plots of χ_M vs. temperature of 4-chloro-2-methoxybenzoates of Mn(II), Co(II), Ni(II) and Cu(II) follow the Curie–Weiss law. The magnetic moment values of Mn²⁺, Co²⁺, Ni²⁺ and Cu²⁺ ions in these complexes were determined in the range of 76−303 K and they change from: 5.88–6.04 μ_B for Mn(C₈H₆ClO₃)₂·4H₂O, 3.96–4.75 μ_B for Co(C₈H₆ClO₃)₂·5H₂O, 2.32–3.02 μ_B for Ni(C₈H₆ClO₃)₂·5H₂O and 1.77–1.94 μ_B for Cu(C₈H₆ClO₃)₂·4H₂O.     

Transition Metal Ions and Amides,VI. Complexation of the neutral and the anionic forms of 3, 7-diazanonanedioic acid diamide and 3, 7-diazanonanedioic acid diethylamide with Cu2+ and Ni2+

Two tetradentate ligands, 3, 7-diazanonanedioic acid diamide (DANA) and 3, 7-diazanonanedioic acid diethylamide (DANEA) have been synthesized and their complexes with Cu²⁺ and Ni²⁺ studied potentiometrically and spectrophotometrically. Three monomeric species, ML, MH_?1L, and MH_?2L, are formed. In ML, the two carbonyl oxygens are bound to the metal ions. Whilst Cu²⁺ gives complexes CuH_?1DANA⁺ and CuH_?1DANEA⁺ with one deprotonated amide group, the corresponding Ni²⁺ chelates do not exist in detectable concentrations. CuH_?2DANA and NiH_?2DANA are formed below pH 9. In the case of the diethyl derivative DANEA, however, steric interaction strongly hinders coordination of two deprotonated amide groups.     

Rational Construction of Polymeric Cadmium(II) Benzimidazole for Transition Metal Ion Exchange

A 1D double‐helical coordination polymer {[Cd(pbbm)₂]₂(ClO₄)₄(H₂O)₂}_n ( 1 ) was successfully constructed by the reaction of Cd(ClO₄)₂ · 6H₂O with 1,1′‐(1,5‐pentanediyl)bis‐1H‐benzimidazole (pbbm). Interestingly, polymer 1 exhibits highly selective capacity for the ionic exchange of Zn²⁺ and Cu²⁺ over Co²⁺ and Ni²⁺ ions in the crystalline solid state when the crystals of 1 are immersed in the aqueous solutions of the perchlorate salts of Cu²⁺, Zn²⁺, Co²⁺, and Ni²⁺ ions, respectively, which indicates that central Cd^II ion exchange might be considered as being dominated by the coordination ability of metal ions to free functional groups, ionic radii of exchanged metal ions, and the solution concentration of adsorbed metal salts. The parent material‐ and ion‐exchange‐induced products are identified by FT‐IR spectroscopy, PXRD patterns as well as SEM and EDS measurements. In addition, the thermal stability of 1 was also investigated.     

Structural and spectropscopic studies of a three‐dimensional hydrogen‐bonded copper(II) complex: aqua[bis(pyridin‐2‐ylcarbonyl)amidato]cyanidocopper(II)

The preparation and X‐ray and spectroscopic studies of the title copper(II) complex, [Cu(C₁₂H₈N₃O₂)(CN)(H₂O)], are reported. The Cu^II cation is five‐coordinated, forming a distorted square‐planar pyramid with an Addison τ parameter of 0.14. The UV–vis spectrum shows a d–d transition of the Cu^II centre at 638 nm, and the electron paramagnetic resonance (EPR) spectrum confirms that the Cu^II cation has an axial symmetry coordination and that the unpaired electrons occupy the d_x2–y2 orbital. Cyclic voltammetric studies show two irreversible oxidation and reduction peaks.     

Spectral, Magnetic, Electrical and Thermal Studies on Malonyl bis(thiosemicarbazide) Complexes

Mono- and binuclear complexes of malonyl bis(thiosemicarbazide), H₄ MBT, with VO²⁺, Co²⁺, Ni²⁺, Cu²⁺, Cd²⁺ and Pt⁴+ have been isolated. The elemental analyses, magnetic moments, spectra [u.v.–vis., i.r., e.s.r. (for Cu²⁺; VO²⁺) and mass], thermal and voltammetric measurements [for Co²⁺ and Ni²⁺] have been used to characterize the isolated complexes. The ligand behaves as binegative quadridentate with Cu²⁺, Co²⁺ and VO²⁺ ions, binegative pentadentate with Pt⁴+ and hexadentate, either as trinegative in [Cd₂(HMBT)(OC₂H₅)(C₂H₅OH)]H₂O or mononegative in [Ni₂(H₃MBT)(OAc)₃(C₂H₅OH)]. The lack of thiol and/or enol hydrogen during the complex formation was confirmed pH-metrically. The pK’s (10.70, 8.50 and 8.15) of H₄MBT reveal the removal of CSNH protons in one step and CONH in two steps. Also, the stability constants reveal a higher value for the Cu²⁺ complex and a lower one for VO²⁺. The TG analyses suggest high stability for most complexes followed by thermal decomposition in different steps. The kinetic and thermodynamic parameters for some decomposition steps in VO²⁺and Pt⁴⁺ thermograms have been calculated     

Synthesis and magnetic properties of binuclear cobalt(Ⅱ), nickel(Ⅱ) and copper(Ⅱ) complexes bridged by oxamidate group

Four binuclear Co(Ⅱ), Ni(Ⅱ) and Cu(Ⅱ) complexes bridged by oxamidate (oxd) group have been synthesized, namely Co2(byp)2(oxd)(ClO4)2 (1), Co2(Me2bpy)2(oxd)(ClO4)2.H2O (2), Ni2(bpy)2(oxd)(ClO4)2.2H2O (3) and Cu2(Me2bpy)2(oxd)(NO3)2 (4). (bpy=2,2'-bipyridyl, Me2-bpy=4,4'-dimethylbipyridyl, oxd=oxamidate) The complexes are characterized by IR, UV spectra, EPR and variable-temperature magnetic susceptibility (4-300 K). The susceptibility data for. complexes 1 and 3 were least-squares fit to the susceptibility equation derived from the spin Hamiltonian H=-2J . S1 . S2. The exchange integral, J, was found to be equal to -3.62 cm-1 in 1 and -1.82 cm-1 in 3. This indicates a weak antiferromagnetic spin exchange interaction between the metal ions.     

Influence of different copper(II) salts on the oxidation and doping reactions of emeraldine base polyaniline

A spectroscopic investigation of the products formed in the reaction of emeraldine base (EB-PANI) with copper(II) ions in dimethylacetamide (DMA) is presented. It is well known that metal cations can dope emeraldine base polyaniline (EB-PANI) through a pseudo-protonation reaction. Resonance Raman, UV–vis-NIR, and EPR data, obtained for Cu²⁺/EB-PANI solutions prepared using CuCl₂·2 H₂O, Cu(NO₃)₂· 3 H₂O or Cu(CH₃COO)₂·H₂O as Cu²⁺ sources, showed that the species formed in reactions of EB-PANI and Cu²⁺ ions are dependent on the anions of the copper salt employed. EPR spectra pointed out that the environments of Cu²⁺ ions with acetate, chloride or nitrate as anions in DMA solution are distinct. Resonance Raman and UV–vis-NIR data demonstrated that the main reactions are the oxidation of EB-PANI to pernigraniline base (PB-PANI) and doping of EB-PANI to ES-PANI (emeraldine salt) when a direct coordination of Cu²⁺ ions to PANI exists. With nitrate as very weak coordinating anion, ES-PANI is formed preferentially. When copper chloride is used, both oxidation and doping of EB-PANI are verified. Conversely with acetate, the dimeric cage structure of this copper salt is preserved in solution, and oxidation of EB-PANI to PB-PANI is the only observed reaction. These results demonstrate the possibility of modulating the products of reaction between Cu²⁺ ions and EB-PANI in DMA solution by changing the counter ion of the Cu²⁺ source.     

N-benzamidosalicylaldimine complexes of copper(II), nickel(II), cobalt(II), iron(II), manganese(II), oxyvanadium(IV) and oxytitanium(IV)

Summary N-benzamidosalicylaldimine (H₂L) complexes of Cu^II, Ni^II, Co^II, Fe^II, Mn^II. VO_IV and TiO_IV have been prepared. The ligand probably coordinates to the metal from the hydroxyl, carbonyl and imino groups.     

A direct fluorescence-on chemo-sensor for selective recognition of Zn(II) by a lower rim 1,3-di-derivative of calix[4]arene possessing bis-{N-(2-hydroxynaphthyl-1-methylimine)} pendants

The bis-{N-(2-hydroxynaphthyl-1-methylimine)} anchored 1,3-di-derivative of lower rim p-tert-butyl-calix[4]arene possessing a N₂O₂, N₂O₄ or N₂O₆ binding core was found to be selective for Zn(II) ions even at ?60 ppb by eliciting fluorescence-on behaviour while the other ions, viz., Ti⁴⁺, VO²⁺, Cr³⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Mg²⁺, Cd²⁺ and Hg²⁺ caused no change in the fluorescence. The reaction between 1 and Zn²⁺ was found to be stoichiometric with the formation of a 1:1 complex; while H⁺ quenched the fluorescence of the complex, OH⁻ restored it. The studies of the 1:1 isolated complexes of Zn²⁺, Ni²⁺ and Cu²⁺ augmented the results.     

N-Formamid osalicylaldimine andN-Acetamidosalicylaldimine Complexes of Copper(II), Nickel(II) and Cobalt(II)

Summary N-formamidosalicylaldimine (H₂SF) andN-acetamidosalicylaldimine (H₂SA) complexes of Cu^II, Ni^II and Co^II have been synthesized and characterized by analytical, spectroscopic and magnetic data. The ligands coordinate to the metalvia the hydroxyl, carbonyl and imino groups to yield normal paramagnetic and insoluble complexes which decompose above 250°.     

Effects of Heteropoly Acids and Surfactant on Electrochemiluminescence of Tris(2,2'-Bipyridine) Ruthenium(II)

ABSTRACT

The effects of heteropoly acids and Triton X-100 on electrochemiluminescence (ECL) of Ru(bpy)₃ ²⁺ are investigated. Triton X-100 prevents the oxidation of oxalate and results in an increase of the ECL signal. H₅SiW₁₁VO₄₀ prevents the direct oxidation of oxalate and makes the electrochemical behavior of Ru(bpy)₃ ²⁺ less reversible, which leads to a decrease of the ECL signal. In contrast, H₃PMo₁₂O₄₀ has negligible effect on ECL intensity. Some possible reasons for the effects on the ECL of Ru(bpy)₃ ²⁺ are discussed based on the adsorption of SiW₁₁VO₄₀ ^5? on electrode surface and the ion association between SiW₁₁VO₄₀ ^5? and Ru(bpy)₃ ²⁺. The signal of ECL decreases linearly with the concentration of heteropoly acid in the range from 2x10^?6 to 1x10^?4 mol 1^?1. The results indicate that ECL of Ru(bpy)₃ ²⁺ is a potential sensitive and selective detection method for heteropoly acids and hence for the elements comprised in them.     

A Highly Copper‐Selective Ratiometric Fluorescent Sensor Based on BODIPY

A new ratiometric fluorescent sensor ( 1 ) for Cu²⁺ based on 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) with di(2‐picolyl)amine (DPA) as ion recognition subunit has been synthesized and investigated in this work. The binding abilities of 1 towards different metal ions such as alkali and alkaline earth metal ions (Na⁺, K⁺, Mg²⁺, Ca²⁺) and other metal ions ( Ba²⁺, Zn²⁺, Cd²⁺, Fe²⁺, Fe³⁺, Pb²⁺, Ni²⁺, Co²⁺, Hg²⁺, Ag⁺) have been examined by UV‐vis and fluorescence spectroscopies. 1 displays high selectivity for Cu²⁺ among all test metal ions and a ～10‐fold fluorescence enhancement in I₅₈₂/I₅₅₈ upon excitation at visible excitation wavelength. The binding mode of 1 and Cu²⁺ is a 1:1 stoichiometry determined via studies of Job plot, the nonlinear fitting of the fluorometric titration and ESI mass.     

Thermal, spectral and magnetic behaviour of 2,3,4-trimethoxybenzoates of Mn(II), Co(II), Ni(II) AND Cu(II)

Four new complexes of 2,3,4-trimethoxybenzoic acid anion with manganese(II), cobalt(II), nickel(II) and copper(II) cations were synthesized, analysed and characterized by standard chemical and physical methods. 2,3,4-Trimethoxybenzoates of Mn(II), Co(II), Ni(II) and Cu(II) are polycrystalline compounds with colours typical for M(II) ions. The carboxylate group in the anhydrous complexes of Mn(II), Co(II) and Ni(II) is monodentate and in that of Cu(II) monohydrate is bidentate bridging one. The anhydrous complexes of Mn(II), Co(II) and Ni(II) heated in air to 1273 K are stable up to 505–517 K. Next in the range of 505–1205 K they decompose to the following oxides: Mn₃O₄, CoO, NiO. The complex of Cu(II) is stable up to 390 K, and next in the range of 390–443 K it loses one molecule of water. The final product of its decomposition is CuO. The solubility in water at 293 K is of the order of 10^–3 mol dm^–3 for the Mn(II) complex and 10^–4 mol dm^–3 for Co(II), Ni(II) and Cu(II) complexes. The magnetic moment values of Mn²⁺, Co²⁺, Ni²⁺ and Cu²⁺ ions in 2,3,4-trimethoxybenzoates experimentally determined in the range of 77–300 K change from 5.64–6.57 μB (for Mn²⁺), 4.73–5.17 μB (for Co²⁺), 3.26–3.35 μB (for Ni²⁺) and 0.27–1.42 μB (for Cu²⁺). 2,3,4-Trimethoxybenzoates of Mn(II), Co(II) and Ni(II) follow the Curie–Weiss law, whereas that of Cu(II) forms a dimer.     

A highly selective turn-on fluorescent chemosensor for copper(II) ion

A new pyrene derivative (1) containing a diaminomaleonitrile moiety exhibits high selectivity for Cu²⁺ detection. Significant fluorescence enhancement was observed with chemosensor 1 in the presence of Cu²⁺. However, the metal ions Ag⁺, Ca²⁺, Cd²⁺, Co²⁺, Fe²⁺, Fe³⁺, Hg²⁺, Mg²⁺, Mn²⁺, Ni²⁺, Pb²⁺, and Zn²⁺ produced only minor changes in fluorescence values for the system. The apparent association constant (K_a) of Cu²⁺ binding in chemosensor 1 was found to be 5.55×10³ M⁻¹. The maximum fluorescence enhancement caused by Cu²⁺ binding in chemosensor 1 was observed over the pH range 5-7.5.     

Hetero-binuclear chelates of Mn(II), Co(II) and Cu(II) o-cresolphthalein complexonates with other metal ions

Heterobinuclear metal chelates of Mn²⁺, Co²⁺ or Cu²⁺ and some transition metal ions with o-cresolphthalein complexone have been prepared and characterized. Elemental analyses are in agreement with proposed formulae. Thermal analyses (TGA and DTA) were used to determine the degradation products; some thermodynamic parameters were calculated. IR and UV-Vis spectra identified the mode of bonding between the metal ions and the ligand as well as its geometry. Magnetic moment determination and ESR spectra of the heterobinuclear complex revealed some antiferromagnetic interaction between the metal ions, which depends mainly on the two metal ions forming the chelate. Electrochemical studies of the complexes [DC-polarography and cyclic voltammetry (CV)] confirmed the existence and the nature of the metal ions in the chelate.     

Syntheses and structures of discrete copper(II) and cadmium(II) supramolecular complexes based on 1,4‐diacylthiosemicarbazone ligands

Thiosemicarbazides and their metal complexes have attracted considerable interest because of their biological activities and their flexibility, which allows the ligands to bend and rotate freely to accommodate the coordination geometries of various metal centres. Discrete copper(II) and cadmium(II) complexes have been prepared by crystallization of N‐[2‐(2‐hydroxybenzoyl)hydrazinecarbonothioyl]propanamide (H₃L) with Cu(CH₃COO)₂ or Cd(NO₃)₂ in a dimethylformamide/methanol mixed‐solvent system at room temperature, affording the complexes di‐μ‐acetato‐bis{μ₄‐1‐[(2‐oxidophenyl)carbonyl]‐2‐(propanamidomethanethioyl)hydrazine‐1,2‐diido}tetracopper(II) dimethylformamide disolvate, [Cu₄(C₁₁H₁₀N₃O₃S)₂(C₂H₃O₂)₂]·2C₃H₇NO, (I), and bis{μ₂‐[(2‐hydroxyphenyl)formamido](propanamidomethanethioyl)azanido}bis[(4,4′‐bipyridine)nitratocadmium(II)] dihydrate, [Cd₂(C₁₁H₁₂N₃O₃S)₂(NO₃)₂(C₁₀H₈N₂)₂]·2H₂O, (II). Complex (I) consists of four Cu^II cations, two μ₄‐bridging trianionic ligands and two μ₂‐bridging acetate ligands, while complex (II) is composed of two Cd^II cations, two μ₂‐bridging monoanionic ligands, two nitrate ligands and two 4,4′‐bipyridine ligands. These discrete complexes are connected by hydrogen bonds and van der Waals interactions to form a three‐dimensional supramolecular architecture. Compared with (I), the phenolic hydroxy group and hydrazide N atom of the thiosemicarbazide ligand of (II) are not involved in coordination and lead to a binuclear Cd^II complex. This different coordination mode may be attributed to the larger ionic radius of the Cd^II ion compared with the Cu^II ion.     

Synthesis,structure, and solvent-extraction properties of tridentate oxime ligands and their cobalt(II), nickel(II), copper(II), zinc(II) complexes

Synthesis of four different types of ligands Ar[COC(NOH)R] _n (Ar = biphenyl, n = 1, HL¹; Ar = biphenyl, n = 2, H₂L²; Ar = diphenylmethane, n = 1, HL³; Ar = diphenylmethane, n = 2, H₂L⁴; R = furfurylamine in all ligands) and their dinuclear Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ complexes is reported herein. These compounds were characterized by elemental analysis, ICP-OES, FT-IR spectra, and magnetic susceptibility measurements. The ligands were further characterized by ¹H NMR. The results suggest that dinuclear complexes of HL¹ and HL³ have a metal to ligand mole ratio of 2: 2 and dinuclear complexes H₂L² and H₂L⁴ have a metal to ligand mole ratio of 2: 1. Square pyramidal or octahedral structures are proposed for complexes of oxime ligands. Furthermore, extraction abilities of the four ligands were also evaluated in chloroform using selected transition metal picrates such as Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺. The ligands show strong binding ability towards Hg²⁺ and Cu²⁺ ions.     

Syntheses,characterization and crystal structures of mixed-ligand Cu(II), Ni(II) and Mn(II) complexes of N-(1-phenyl-3-methyl-4-propenylidene-5-pyrazolone)-salicylidene hydrazide containing ethanol or pyridine as a co-ligand

Five new mixed-ligand complexes [CuL(EtOH)] (1), [NiL(EtOH)₃] (2), [Mn₂L₂(μ₂-EtOH)₂(EtOH)₂] (3), [CuL(Py)] · MeOH (4) and [NiL(Py)₃] (5) (L²⁻ = N-(1-phenyl-3-methyl-4-propenylidene-5-pyrazolone)-salicylidene hydrazide anion, Py = pyridine) have been synthesized and characterized by elemental analyses, IR spectra, thermal analyses and single crystal X-ray diffraction. The crystallographic structural analyses of these complexes reveal that the ligand (H₂L) itself undergoes isomerization from the keto form to the enol form in the reaction, then loses two protons and acts as a double negatively charged tridentate chelating agent coordinated to the metal ion in the solution. The final results show that when a co-ligand was present in the synthetic reaction, other coordination sites around the metal ions Cu²⁺ and Ni²⁺ were completed either by the ethanol or pyridine molecules under the common solvent reaction or solvothermal syntheses conditions, respectively. In the case of the Mn²⁺ ion, it was still coordinated with the solvent molecules regardless of whether it was synthesized under the common solvent reaction or solvothermal syntheses with pyridine. The reason for this difference might be attributed to the fact that the coordination modes and bonding effect of the co-ligand with the metal ions are different, the final complexes tend to form the most stable compound.