Synthesis,spectroscopic and thermodynamic studies of new transition metal complexes with N,N′-bis(2-hydroxynaphthalin-1-carbaldehydene)-1,2-bis(m-aminophenoxy)ethane and their determination by spectrophotometric methods

A novel tetradentate N₂O₂-type Schiff base, synthesized from 1,2-bis(m-aminophenoxy)ethane and 2-hydroxynaphthalin-1-carbaldehyde, forms stable complexes with transition metal ions such as Cu(II), VO(IV) and Zn(II) in DMF. Microanalytical data, elemental analysis, magnetic measurements, UV, visible and IR spectra as well as conductance measurements were used to confirm the structures. The stability constants of these complexes in 60% (v/v) DMF–water were determined at different ionic strengths (0.07,?0.13,?0.2?M) and at different temperatures (45,?50,?55,?60?±?0.1°C) using a spectrophotometric method. From these constants, thermodynamic stability constants and thermodynamic parameters (ΔG?⁰, ΔH?⁰, ΔS?⁰) were calculated. The values of enthalpy change are negative for all systems. The acid dissociation constant of the ligand, investigated in 60% (v/v) DMF–water, has also been calculated at different temperatures.     

The thermal properties of cobalt(II), nickel(II) and copper(II) iminodiacetates

The thermal properties of the Cu(II), Ni(II) and Co(II) complexes of iminodiacetic acid (H₂IMDA) were determined using TG, DTG and DSC techniques. The complexes, of general formula, MIMDA-2H₂O evolved water of hydration from 50 to 150°C which was followed by the decomposition of the anhydrous complex in the 250 to 400°C temperature range. The thermal stability, as determined by procedural decomposition temperatures, was: Ni(II) >Co(II) >Cu(II). The thermal stability is discussed in terms of IR spectra, ΔH, and ΔS, as well as thermal data.     

Synthesis, spectral studies, and determination of stability constants and thermodynamic parameters for some aromatic diamine transition-metal complexes

The Cu(II) and Zn(II) complexes of aromatic bidentate diamines were prepared and characterized by different analytical and spectral methods. Thermodynamic parameters of complexes of Cu(II) and Zn(II) cations with 1,3-bis(p-aminophenoxy)propane were determined in 60 vol. % DMF-H₂O at various ionic strengths (0.07, 0.13, 0.2 M NaNO₃) and different temperatures (45, 50, 55, 60 ± 0.1°C) using a spectrophotometric method. The NaNO₃ solution was used to maintain the ionic strength. The stability constants show an inverse relationship with ionic strengths. The thermodynamic parameters of 60 vol. % DMF-H₂O (ΔG°, ΔH°, ΔS°) based on these formation constants were determined. The text was submitted by the authors in English.     

Fluorescence Quenching Study on the Interaction of Some Schiff Base Complexes with Bovine Serum Albumin

The interaction of Schiff base ligand A and its three metal complexes [A‐Fe(II), A‐Cu(II), and A‐Zn(II)] with bovine serum albumin (BSA) was investigated using a tryptophan fluorescence quenching method. The Schiff base ligand A and its three metal complexes all showed quenching of BSA fluorescence in a Tris‐HCl buffer. Quenching constants were determined for quenching BSA by the Schiff base ligand A and its metal complexes in a Tris‐HCl buffer (pH=7.4) at different temperatures. The experimental results show that the dynamic quenching constant (K_SV) was increased with increasing temperature, whereas the association constant (K) was decreased with the increase of temperature. The thermodynamic parameters ΔH, ΔG and ΔS at different temperatures were calculated. The ionic strength of the Tris‐HCl buffer had a great influence on the wavelength of maximum emission of BSA. Under low ionic strength, the emission spectra of BSA influenced by A‐Zn(II) had a small blue shift. Compared to A‐Zn(II), the emission spectra of BSA in the presence of the Schiff base ligand A and A‐Cu(II) had no significant λ_em shift. At high ionic strength, the emission spectra of BSA upon addition of the Schiff base A, A‐Fe(II), and A‐Zn(II) all had a red shift, but the emission spectra of BSA had λ_em shift neither at low ionic strength, nor at high ionic strength in the presence of A‐Cu(II). Furthermore, the temperature did not affect the λ_em shift of BSA emission spectra.     

Thermodynamics,formation constants,spectrophotometry and infrared spectroscopy of complexes between some divalent metal ions and 3-hydrazino-6-phenylpyridazine and related ligands

The stepwise formation constants of complexes of Cu(II), Ni(II), Co(II), Mn(II), Zn(II), Cd(II) and UO₂(II) ions with 3-hydrazino-6-phenylpyridazine (HPP) and its condensation products with benzil (BHPP) and p-methoxyacetophenone (p-MeOAHPP) were determined in a 75% (v/v) dioxane-water mixture at μ = 0.05 M (KNC₃). The effect of temperature (at 10, 20, 30 and 40 °C) was also examined for Cu(II) and UO₂(II)-BHPP complexes. The overall changes in ΔG, ΔH and ΔS have been calculated. The solid complexes of Cu(II)-, Co(II)- and Ni(II)-BHPP were prepared and examined by elemental analysis and IR spectroscopy. Analysis of the data indicates chelation of the BHPP ligand through the nitrogens of both hydrazone and the pyridazine ring and the carbonyl oxygen group. The spectrophotometric studies were performed on solutions of Cu(II), Ni(II) and Co(II) with BHPP in order to obtain the optimum pH values for complex formation. The compositions of the chelates formed were determined. Analytical determinations of the micro amounts of Cu(II), Ni(II) and Co(II) were also done using BHPP as the complexing agent.     

Spectroscopic characterization,thermogravimetry, density functional theory and biological studies of some mixed‐ligand complexes of meloxicam and 2,2′‐bipyridine with some transition metals

The mixed‐ligand Mn(II), Fe(III), Ni(II), Cu(II), Zn(II) and Zr(IV) complexes of meloxicam (H₂mel) and 2,2′‐bipyridine (Bipy) were prepared and characterized. For all complexes, the analytical and spectroscopic results revealed that H₂mel acts in a monobasic bidentate manner through the oxygen of the amide and nitrogen of the thiazole groups, whereas Bipy coordinates through the two nitrogen atoms with slightly distorted octahedral geometry. Thermodynamic parameters (E, ΔS^*, ΔH^* and ΔG^*) were calculated using Coats–Redfern and Horowitz–Metzger methods. The geometries of H₂mel and the complexes were carefully studied using density functional theory to predict the properties of materials performed using the hybrid density functional method B3LYP. All studied complexes are soft with respect to H₂mel where η varies from 0.096 for Zn(II) complex to 0.067 for Fe(III) complex and σ varies from 10.42 to 14.93 eV, while η and σ for H₂mel are 0.14 and 7.14 eV, respectively. The antibacterial activities of the ligands and metal complexes were investigated and the data show that the complexes are active against some bacterial species compared with H₂mel.     

Spectroscopic and thermodynamic studies of complexation of some divalent metal ions with isatin-<Emphasis Type="Italic">β</Emphasis>-thiosemicarbazone

Metal complexes of some divalent metal ions (Co, Ni, Cu, Zn, Hg, and Pd) with isatin-β-thiosemicarbazone (ITS) as the Schiff base have been investigated potentiometrically and spectrophotometrically. The dissociation constants of the ligand and formation constants of the metal complexes, as well as the corresponding thermodynamic functions (ΔG, ΔH and ΔS) have been determined at different temperatures in ethanol—water solution. The full stability constants were also evaluated spectrophotometrically by the Job method. The experimental results indicate that Cu(II), Zn(II), Pd(II), and Hg(II) form one-to-one molecular complexes (ML) with the studied ligand, whereas Co(II) and Ni(II) form both ML and ML₂ species.     

Thermodynamics of ion association XXV. Transition metal complexes of proline and hydroxyproline

Calorimetric and potentiometric measurements have been made at 25°C of the formation of the mono- and bis-hydroxyproline complexes of cobalt(II), nickel(II), copper(II) and zinc(II) and the proline complexes of copper(II) and nickel(II). The data have been used to calculate ΔG, ΔH and ΔS values for both protonation and metal complexation and these are discussed in terms of the nature of the metal—ligand binding.     

Spectral and thermal studies of alloxan complexes

The complexes of alloxan with Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) Cd(II), Hg(II), Ti(IV) and Zr(II) have been isolated and characterized on the basis of elemental analysis, molar conductivity, spectral studies (mid infrared, ¹H-NMR and UV/vis spectra), X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The thermal decomposition of the metal complexes was studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The kinetic thermodynamic parameters, E*, ΔH*, ΔS* and ΔG*, were calculated using Coats and Redfern and Horowitz and Metzger equations. The ligand and its complexes have been studied for possible biological activity including antibacterial and antifungal activity.     

Thermodynamic studies of inclusion complex between cetyltrimethylammonium bromide (CTAB) and β -cyclodextrin ( β -CD) in water/n-butanol mixture,using potentiometric technique

The behaviour of the inclusion complex consisting of cetyltrimethylammonium bromide (CTAB) and β-cyclodextrin (β-CD) in water/n-butanol mixture was studied using ion selective electrodes sensitive to surfactant ions. The experiments were carried out at different temperatures and different composition of water/alcohol. The data obtained indicate that the inclusion complexes S(CD) and S(CD)₂ had formed between CTAB and β-CD in water/alcohol mixture environment. In addition to the 1 : 1 complex, CTAB formed 1 : 2 complexes with β-CD. Further investigation showed that K ₁ for S(CD) was greater than K ₂ for S(CD)₂, and the values of K_i were reduced with increasing butanol concentration. Finally, thermodynamic parameters of the complexation, i.e. ΔH°, ΔG° and ΔS° were also calculated. The obtained thermodynamic data showed that the hydrophobic interaction is the main factor for inclusion complex formation and tendency of complex formation has been reduced with increasing of medium hydrophobicity.     

New complexes of some d-electron elements with 3-methyladipic acid

Conditions for the preparation of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) 3-methyladipates were investigated and their qualitative composition and magnetic moments were determined. The IR spectra and powder diffraction patterns of the complexes prepared of the general formula M(C₇H₁₀O₄)·nH₂O (n=0-11) were recorded and their thermal decomposition in air were studied. During heating the hydrated complexes are dehydrated in one (Co, Ni) or two steps (Mn, Zn) losing all crystallization water molecules (Co, Ni) or some water molecules (Mn, Zn) and then anhydrous (Co, Ni, Cu) or hydrated complexes (Mn, Zn) decompose directly to oxides (Mn, Co, Zn) or with intermediate formation the mixture of M+MO (Ni, Cu). The carboxylate groups are bidentate (Mn, Co, Ni, Cu) or monodentate (Zn). The complexes exist as polymers. The magnetic moments for the paramagnetic complexes of Mn(II), Co(II), Ni(II) and Cu(II) attain values 5.48, 4.49, 2.84 and 1.45 B.M., respectively. This revised version was published online in July 2006 with corrections to the Cover Date.     

Formation constants and coordination thermodynamics for binary complexes of Cu(II) and some α-amino acids in aqueous solution

In this study, the formation constants of 1?:?1 binary complexes of Cu(II) with L-glutamic acid, L-aspartic acid, glycine, L-alanine, L-valine, and L-leucine and 1?:?2 binary complexes of L-glutamic acid, glycine and the protonation macro- and microconstants of all these amino acids were determined potentiometrically in aqueous solutions at 5.0, 20.0, and 35.0°C at a constant ionic strength of I?=?0.10?mol?L^?1 (NaClO₄). The thermodynamic parameters ΔG _f°, ΔH _f°, and ΔS _f° were determined for the protonation of all amino acids used in this study and for the complex formation reactions of them with Cu(II). The results were analysed by means of Principle of hard and soft [Lewis] acids and bases. Additionally, in order to confirm the complex formation and determine the stability constants of complexes, UV-Vis spectroscopic studies were carried out. The stability constants obtained by spectrophotometrically are confirmed by those determined potentiometrically.     

Spectrothermal studies on Co(II), Ni(II), Cu(II) and Zn(II) salicylato (1,10-phenanthroline) complexes

The cobalt, nickel, copper and zinc atoms in bis(1,10-phenanthroline)bis(salicylato-O)metal(II) monomeric octahedral complexes [M(Hsal)₂(phen)₂]·nH₂O, (M: Co(II), n=1; Cu(II), n=1.5 and Ni(II), Zn(II), n=2) are coordinated by the salicylato monoanion (Hsal) through the carboxyl oxygen in a monodentate fashion and by the 1,10-phenanthroline (phen) molecule through the two amine nitrogen atoms in a bidentate chelating manner. On the basis of the DTG_max, the thermal stability of the hydrated complexes follows order: Ni(II) (149°C)>Co(II) (134°C)>Zn(II) (132°C)>Cu(II) (68°C) in static air atmosphere. In the second stage, the pyrolysis of the anhydrous complexes takes place. The third stage of decomposition is associated with a strong exothermic oxidation process (DTA curves: 410, 453, 500 and 450°C for the Co(II), Ni(II), Cu(II) and Zn(II) complexes, respectively). The final decomposition products, namely CoO, NiO, CuO and ZnO, were identified by IR spectroscopy. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal properties of cobalt(II), nickel(II) and copper(II) glycinates and iminodiacetates. Critical comparison

The thermal properties of the Co(II), Ni(II) and Cu(II) complexes of iminodiacetic acid (H₂IDA) and of glycine were determined using TG, DTG and DSC techniques. The thermal properties of the two series were compared and discussed in terms of IR spectra, ΔH, ΔG and ΔS for the formation of the complexes in aqueous solutions, as well as the thermal data.     

Coordination polymers of glutaraldehyde with glycine metal complexes: synthesis,spectral characterization,and their biological evaluation

Glycine metal complexes were prepared by the reaction of glycine with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) in 1?:?2 molar ratio. Thereafter their condensation polymerization was done with glutaraldehyde to obtain polymer metal complexes. All the synthesized polymer metal complexes were characterized by elemental analysis, FT-IR, ¹H-NMR, and UV-Vis spectrometry, magnetic susceptibility, and thermogravimetric studies. The analytical data of all the polymers agreed with 1?:?1 molar ratio of metal complex to glutaraldehyde and magnetic moment data suggest that PGG–Mn(II), PGG–Co(II), PGG–Ni(II), and PGG–Cu(II) have an octahedral geometry around the metal atom, whereas the tetrahedral geometry was proposed for PGG–Zn(II) polymer. The PGG–Mn(II) and PGG–Cu(II) showed octahedral geometry. Thermal behavior of the polymer metal complexes was obtained at a heating rate of 10°C?min^?1 under nitrogen atmosphere from 0°C to 800°C. The antimicrobial activities of synthesized polymers were investigated against Streptococcus aureus, Escherichia coli, Bacillus sphaericus, Salmonella sp. (Bacteria), Fusarium oryzae, Candida albicans, and Aspergillus niger (Yeast).     

Synthesis,characterization and antimicrobial activity of a new macrocycle and its transition metal complexes

The semicarbazone (L¹) has been prepared by reaction of semicarbazide and glutaraldehyde (2 : 1) in distilled water and methanol (1 : 1). The reaction of semicarbazide, glutaraldehyde and diethyl oxalate in distilled water and methanol gave Schiff-base L², 1,2,4,7,9,10-hexaazacyclo-pentadeca-10,15-dien-3,5,6,8-tetraone. Complexes of first row transition metal ions Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) have also been synthesized. The ligand and its complexes were characterized by elemental analysis, molar conductance, magnetic moment measurements, IR, ¹H NMR, UV–Visible spectra and thermogravimetric analysis (TGA). Molar conductance values show that the complexes of Ni(II), Cu(II), Zn(II), Mn(II) and Co(II) are 1 : 2 electrolytes. On the basis of electronic spectral studies and molar conductance measurements an octahedral structure has been proposed for Mn(II) and Co(II) complexes, tetrahedral for Zn(II) complex and square planar for Ni(II) and Cu(II). The thermal behavior of the compounds, studied by TGA in a nitrogen atmosphere up to 800°C, reveal that the complexes have higher thermal stability than the macrocycle. All the synthesized compounds and standard drugs kanamycin (antibacterial) and miconazole (antifungal) have been screened against bacterial strains Staphylococcus areus, Escherichia coli and fungal strains Candida albicans, Aspergillus niger. The metal complexes inhibit growth of bacteria to a greater extent than the ligand.     

Synthesis,structural determination and HSA interaction studies of a new water-soluble Cu(II) complex derived from 1,10-phenanthroline and ranitidine drug

A new water-soluble Cu(II) complex containing ranitidine drug and 1,10-phenanthroline was synthesized and characterized by elemental analysis, molar conductivity, spectroscopic and computational methods. In vitro human serum albumin (HSA)-interaction studies of Cu(II) complex were performed by employing fluorescence spectroscopy in combination with UV–vis absorption and circular dichroism (CD) spectroscopies. The results of fluorescence titration showed that Cu(II) complex strongly quenched the intrinsic fluorescence of HSA through a static quenching mechanism with an intrinsic binding constant (6.05 × 10⁴ M^?1) at 286 K. The thermodynamic parameters ΔG, ΔH, and ΔS at different temperatures were calculated and suggested that the hydrophobic and hydrogen bonding interactions play major roles in Cu(II) complex-HSA association. The displacement experiments using warfarin and ibuprofen as site I and II probes proved that the Cu(II) complex could bind to site I (subdomain IIA) of HSA. Finally, CD spectra indicated that the interaction of the Cu(II) complex with HSA leads to an increase in the α-helical content. The main result of this study was the finding that the binding affinity of the Cu(II) complex to HSA is three orders of magnitude stronger than that of ranitidine drug.     

Spectral,thermal and magnetic investigations of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) 4-methylphthalates

Conditions for the preparation of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) 4-methylphthalates were investigated and their composition, solubility in water at 295 K and magnetic moments were determined. IR spectra and powder diffraction patterns of the complexes prepared with molar ratio of metal to organic ligand of 1.0:1.0 and general formula: M [ CH₃C₆H₃(CO₂)₂]·nH₂o (n=1-3) were recorded and their decomposition in air were studied. During heating the hydrated complexes are dehydrated in one (Mn, Co, Ni, Zn, Cd) or two steps (Cu) and next the anhydrous complexes decompose to oxides directly (Cu, Zn), with intermediate formation of carbonates (Mn, Cd), oxocarbonates (Ni) or carbonate and free metal (Co). The carboxylate groups in the complexes studied are mono- and bidentate (Co, Ni), bidentate chelating and bridging (Zn) or bidentate chelating (Mn, Cu, Cd). The magnetic moments for paramagnetic complexes of Mn(II), Co(II), Ni(II) and Cu(II) attain values 5.92, 5.05, 3.36 and 1.96 M.B., respectively. This revised version was published online in July 2006 with corrections to the Cover Date.     

Kinetic of Patent Blue VF Adsorption from Aqueous Solution on Activated Bone Charcoal

The effect of temperature of activation on bone charcoal, used as adsorbent for the removal of Patent Blue VF from water solutions was studied. The adsorbent was characterized by FTIR, XRD, SEM and EDS. The kinetic of adsorption of dye was carried out at 10 °C and 45 °C. Carbonization temperature (600–1000 °C) of the adsorbent has significant effect on the removal of dye from water solutions. The first order kinetic, Elovich, Bangham, parabolic diffusion and power function equations were found to fit the kinetic data. Activation energies of adsorption (Δ≠) have higher values for the charcoal activated at high temperatures and the other thermodynamic parameters like ΔH≠, ΔS≠ and ΔG≠ were also found.     

Thermodynamic studies of hydrogen iodide in dioxane-water mixtures from electromotive force measurements

The standard potentials of the silver-silver iodide electrode were measured in 10,20,30 and 40% (w/w) dioxane-water mixtures at 15,25,35 and 45°C. These values have been used to determine the thermodynamic quantities ΔG_t°, ΔS_t°, ΔH_t° for the transfer of H⁺I^? from water to various dioxane-water mixtures. The ionic ΔG_t° values for H⁺, Cl^?, Br^? and I^? are determined using Feakins method. The chemical and electrical contributions of ΔG_t° are also calculated using the method proposed by Roy and co-workers. The significance of these thermodynamic functions is discussed in relation to the acid—base character of the solvents.