Spectroscopic characterization,thermogravimetric and antimicrobial studies of some new metal complexes derived from4-(4-Isopropyl phenyl)-2-oxo-6-phenyl 1,2-dihyropyridine-3-carbonitrile (L)

A new series of Fe (III), Co (II), Zn (II), Y (III), Zr (IV) and La (III) complexes derived from the novel ligand 4-(4-Isopropyl phenyl)-2-oxo-6-phenyl 1,2-dihyropyridine-3-carbonitrile (L) were synthesized and characterized. The mode of bonding of L and geometrical structures of their metal complexes were elucidated by different micro analytical and spectral methods (FT-IR,UV–visible,1H NMR and Mass spectra) as well as thermal analysis (TG and DTG), and differential scanning calorimetry (DSC). The results of analytical and spectroscopic equipments revealed that L acts as bidentate through nitrogen of carbonitrile group and oxygen of keto group. The conductivity measurement results deduced that these chelates are electrolyte with 1:2 for Co (II), Zn (II), and Zr (IV) and 1:3 for Fe (III), Y (III), and La (III). The results of magnetic moment measurements supported paramagnetic for some complexes (Fe (III), Co (II) and Cu (II)) and diamagnetic phenomena for the other complexes (Y (III), Zr (IV) and La (III)). Thermodynamic parameters such as energy of activation E*, entropy ΔS*, enthalpy ΔH* and Gibss free energy ΔG* were calculated using Coats-Redfern and Horowitz-Metzeger methods at n = 1 or n#1. Some results of bioactivity tests for ligands and their metal complexes were recorded against Gram-positive, Gram-negative bacteria and antifungal. The complexes showed significant more than free ligand.     

Divalent manganese,cobalt, copper and cadmium complexes of (Z)‐N‐benzoyl‐N′‐(1H‐1,2,4‐triazol‐3‐yl)carbamimidothioic acid: Preparation,characterization, computational and biological studies

In this work, (Z)‐N‐benzoyl‐N′‐(1H‐1,2,4‐triazol‐3‐yl)carbamimidothioic acid and its Mn(II), Co(II), Cu(II) and Cd(II) complexes were introduced for the first time. This carbonyl thiourea ligand was prepared by the reaction of 1H‐1,2,4‐triazol‐3‐amine with benzoyl isothiocyanate. The structural elucidation of these compounds was performed using elemental analysis and spectral and magnetic measurements. Octahedral structures of all complexes, except Cd(II) complex with a tetrahedral geometry, were confirmed by applying DFT structural optimization. The thermal decomposition behaviour of metal complexes of carbonyl thiourea ligand is discussed. The calculation of kinetic parameters for prepared complexes (E_a, A, ΔH*, ΔS* and ΔG*) of all thermal degradation stages has been evaluated using two comparable approaches. Antimicrobial and ABTS‐antioxidant studies indicated potent activity of Cd(II) complex compared with the other investigated compounds. The cytotoxic activity of the prepared compounds was investigated in vitro. The results indicated potent activity of Mn(II) complex against both HePG2 (liver carcinoma) and MCF‐7 (breast carcinoma) cancer cells.     

Synthesis, structural, thermal studies and biological activity of a tridentate Schiff base ligand and their transition metal complexes

Schiff base (L) ligand is prepared via condensation of pyridine-2,6-dicarboxaldehyde with -2-aminopyridine. The ligand and its metal complexes are characterized based on elemental analysis, mass, IR, solid reflectance, magnetic moment, molar conductance, and thermal analyses (TG, DTG and DTA). The molar conductance reveals that all the metal chelates are non-electrolytes. IR spectra shows that L ligand behaves as neutral tridentate ligand and bind to the metal ions via the two azomethine N and pyridine N. From the magnetic and solid reflectance spectra, it is found that the geometrical structures of these complexes are octahedral (Cr(III), Fe(III), Co(II), Ni(II), Cu(II), and Th(IV)) and tetrahedral (Mn(II), Cd(II), Zn(II), and UO2(II)). The thermal behaviour of these chelates shows that the hydrated complexes losses water molecules of hydration in the first step followed immediately by decomposition of the anions and ligand molecules in the subsequent steps. The activation thermodynamic parameters, such as, E*, ΔH*, ΔS* and ΔG* are calculated from the DTG curves using Coats-Redfern method. The synthesized ligand, in comparison to their metal complexes also was screened for its antibacterial activity against bacterial species, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus pyogones and Fungi (Candida). The activity data shows that the metal complexes to be more potent/antibacterial than the parent Schiff base ligand against one or more bacterial species.     

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.     

Synthesis,spectroscopic, biological,and theoretical studies of new complexes from (E)-3-(2-(5, 6- diphenyl-1,2,4- triazin-3- yl)hydrazono)butan-2- one oxime

New mononuclear Fe (III), Cu (II), Ag (I), ZrO ( IV) and UO₂(VI) complexes were synthesized by the reaction of metal ions with (E)-3-(2-(5, 6- diphenyl-1,2,4- triazin-3- yl)hydrazono)butan-2- one oxime. The structures of the metal complexes were characterized using analytical, spectral (infrared, electronic, ¹H NMR, electron spin resonance (ESR), and mass), magnetic moment, molar conductance, thermal gravimetric analysis, and powder X-ray diffraction (XRD) measurements. All complexes have octahedral geometries except the Cu (II) complex, which has square planar geometry, and the UO₂(VI) complex, in which the coordination number is seven. The ligand acts as a (neutral, monoanionic or dianionic) tridentate with N₂O coordinating sites: N-azomethine, N-triazine, and O-oxime. Fluorescence spectral studies were carried out in solid state and in dimethylformamide (DMF). The kinetic parameters of the thermal decomposition stages were calculated using Coats–Redfern equations. The morphological structures of the ligand and some complexes were determined using XRD. The molecular orbital calculations were carried out for the ligand and metal complexes using the Hyperchem 7.52 program on the basis of the PM3 level. The antimicrobial activities of the ligand and its complexes were investigated towards the microorganisms S. aureus and B. subtilis as Gram-positive bacteria, S. typhimurium and E. coli as Gram-negative bacteria, C. albicans, and A. fumigatus. The ligand and its complexes showed antitumor activity against Hep G-2 cell lines, where Cu (II) and Ag (I) complexes seem to be promising as they showed IC₅₀ values that are lower than and comparable to that of the antitumor drug doxorubicin.     

Novel Cr(III), Ni(II), and Zn(II) complexes of thiocarbamide derivative: Synthesis,investigation, theoretical,catalytic, potentiometric,molecular docking and biological studies

Throughout this research, the thiocarbamide derivative (H₂L), and its Cr(III), Ni(II) and Zn(II) complexes have been reported. The thiocarbamide moiety was established with a reaction of benzoyl isothiocyanate and 1H-1,2,4-triazol-3-amine. Structural elucidation of such compounds was achieved using elementary examination, spectral and magnetic experiments. The octahedral construction of the Cr(III) complex, the tetrahedral geometry of the Zn(III) complex and the mixed geometry (tetrahedral and square planar) of the Ni(II) complex have been verified by the optimization of structure using DFT. The action of Zn²⁺ complex in the oxidative degradation of an organic azo-dye was investigated, and it showed promising results. The thermal degradation behavior of thiocarbamide metal complexes were studied as well as the calculation of the kinetic data for title compounds (E_a, A, ΔH*, ΔS* and ΔG*) of thermal degradation steps has been tested utilizing two different techniques. Liver carcinoma (HePG2) and breast carcinoma (MCF-7) cytotoxicity as well as ABTS-antioxidant activities demonstrated the effective inhibitory of the Ni(II)-complex relative to other tested compounds. The antimicrobial activity of the compounds suggests that Cr(III) has the highest activity. Furthermore, the Molecular Operating Environment (MOE) program was used to calculate the binding affinity between the EGFR protein and the compounds under investigation.     

Ligational,DFT modeling and biological properties of some new metal complexes with 3-(bromoacetyl)coumarin and 1,10-phenanthroline

The synthesis and characterization of Mn (II), Fe (II), Co (II), Ni (II), Cu (II) and Zn (II) complexes with 3-(bromoacetyl)coumarin (BAC) in presence of 1,10-phenanthroline (Phen) were reported and described by elemental analysis, molar conductivity, FT-IR, UV–Vis and effective magnetic moments. TG and DTG have been applied to study the decomposition mechanisms for BAC, Phen and their complexes. The analytical results and spectral studies showed that BAC and Phen act as bidentate ligands via oxygen of α, β-unsaturated ketone and oxygen of lactone carbonyl of coumarin and two pyridyl nitrogen atoms of Phen. Octahedral geometries have been proposed for all complexes and the kinetic parameter (E*, ΔH*, ΔS* and ΔG*) were calculated using Coats-Redfern (CR) and Horowitz-Metzeger (HM) methods. DFT calculations (bond lengths, bond angles, total energy, heat of formation, dipole moment and the lowest energy model structures) have been determined. The antibacterial activities for synthesized complexes were assayed against some selected bacterial and the complexes displayed a very highly significant against L. monocytogens.     

Green Synthesis of new Trizole Based Heterocyclic Amino Acids Ligands and their Transition Metal Complexes. Characterization,Kinetics, Antimicrobial and Docking Studies

Two novel amino acids imine ligands (H₂L₁ and H₂L₂) have been synthesized using green condensation reaction from 2‐[3‐Amino‐5‐(2‐hydroxy‐phenyl)‐5‐methyl‐1,5‐dihydro‐[1, 2, 4]triazol‐4‐yl]‐3‐(1H‐indol‐3‐yl)‐propionic acid with benzaldehyde/p‐flouro benzaldehyde (1:1 molar ratio) in the presence of lemon juice as a natural acidic catalyst in aqueous medium. Their transition metal complexes have been prepared in a molar ratio (1:1). Characterization of the ligands and complexes using elemental analysis, spectroscopic studies, ¹HNMR, ¹³CNMR, and thermal analysis has been reported. E*, ΔH*, ΔS* and ΔG* thermodynamic parameters, were calculated to throw more light on the nature of changes accompanying the thermal decomposition process of these complexes. The molar conductance measurement of metal complexes showed nonelectrolyte behavior. The metal complexes of the two ligands have tetrahedral geometry with a general molecular structure [M(H₂L)X_n], where [(M = Mn (II), Co (II), Cu (II) and Zn (II), X = Cl, n = 2]; M = VO (II), X = SO₄, n = 1] for H₂L₁. [M = Co (II), Cu (II), Zn (II)] for H₂L₂. Antibacterial activity of the complexes against (Bacillis subtilis, Micrococcus luteus, Escherichia coli), also antifungal activity against (Aspergillus niger, Candida Glabarta, Saccharomyces cerevisiae) have been screened. The results showed that all complexes have antimicrobial activity higher than free ligands. Molecular docking studies results showed that, all the synthesized compounds having minimum binding energy and have good affinity toward the active pocket, thus, they may be considered as good inhibitor of targeting PDB code: 1SC7 (Human DNA Topo‐isomerase I).     

Investigations of preferential solvation on 1,4-dimethoxy-3-methyl anthracene-9,10-dione

Synthesis, spectroscopic and thermal studies of some complexes of a new N(2)-Schiff base ligand of N(1),N(2)-bis((E)-2-methyl-3-phenylallylidene)ethane-1,2-diamine (L) with a general formula of MLX(2) (M = Zn(II), Cd(II) and Hg(II); X = Cl(-), Br(-), I(-), SCN(-) and N(3)(-)) are described. The ligand and its complexes were characterized by elemental analysis, molar conductance, UV-vis spectra, FT-IR spectra, MS, (1)H NMR and (13)C NMR spectra. The conductivity measurement as well as spectral data indicated that the complexes are non-electrolyte. (1)H and (13)C NMR spectra have been studied in DMSO-d(6) and/or CDCl(3). The thermal behavior of the complexes shows weight loss by decomposition of the anions and ligand segments in the subsequent steps. Activation thermodynamic parameters of decomposition such as E*, ΔH*, ΔS* and ΔG* were calculated from TG curves.     

Spectral and Thermal Studies of Some New Metal Complexes Derived from N-[(Phenylamino)Thioxomethyl] Hydrazinocarbonyl Methyl Pyridinium Chloride (PTHMPC)

New metal complexes derived from the reaction of N-[(phenylamino)thioxomethyl] hydrazino carbonyl methyl pyridinium chloride (H₂L; PTHMPC) with some metal salts of the general formula MX₂ [(X = Cl^? and/or CH₃COO^?; M = Cd(II), UO₂(II), Mn(II) and Zr(IV)] were synthesized and characterized by elemental analyses, spectral analyses (IR, UV-vis., ¹H NMR), thermal analyses (TGA, DTG), and conductance and magnetic measurements. The results showed that the ligand exists in metal complexes either in the keto form or in the enol form. Moreover, the IR spectral data suggest that the acetate ion behaves in a monodentate manner. Semi-empirical calculations ZINDO/1, PM3, and AM1 have been used to study the molecular geometry and the harmonic vibrational spectra of the ligand and its metal complexes with the purpose of assisting the experimental assignment of the complexes. Generally, there is an agreement between the observed and the calculated spectra. Finally, the thermodynamic parameters (ΔE*, ΔH, ΔG, and ΔS) have been calculated from the data of thermal analyses (TGA and DTG).

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Potentiometric, spectroscopic and thermal studies on the metal chelates of 1-(2-thiazolylazo)-2-naphthalenol

The synthesis and characterization of Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Pd(II) and UO2(II) chelates of 1-(2-thiazolylazo)-2-naphthalenol (TAN) were reported. The dissociation constants of the ligand and the stability constants of the metal complexes were calculated pH-metrically at 25 degrees C and 0.1 M ionic strength. The solid complexes were characterized by elemental and thermal analyses, molar conductance, IR, magnetic and diffuse reflectance spectra. The complexes were found to have the formulae [M(L)2] for M = Mn(II), Co(II), Ni(II), Zn(II) and Cd(II); [M(L)X].nH2O for M = Cu(II) (X = AcO, n = 3), Pd(II) (X = Cl, n = 0) and UO2(II) (X = NO3, n = 0), and [Fe(L)Cl2(H2O)].2H2O. The molar conductance data reveal that the chelates are non-electrolytes. IR spectra show that the ligand is coordinated to the metal ions in a terdentate manner with ONN donor sites of the naphthyl OH, azo N and thiazole N. An octahedral structure is proposed for Mn(II), Fe(III), Co(II), Ni(II), Zn(II), Cd(II) and UO2(II) complexes and a square planar structure for Cu(II) and Pd(II) complexes. The thermal behaviour of these chelates shows that water molecules (coordinated and hydrated) and anions are removed in two successive steps followed immediately by decomposition of the ligand molecule in the subsequent steps. The relative thermal stability of the chelates is evaluated. The final decomposition products are found to be the corresponding metal oxides. The thermodynamic activation parameters, such as E*, delta H*, delta S* and delta G* are calculated from the TG curves.     

Studies of Mn(II), Co(II), Ni(II) and Cu(II) Chelates with 3-phenyl-4-(p-methoxy- phenylazo)-5-pyrazolone

Mn(II), Co(II), Ni(II) and Cu(II) chelates with3-phenyl-4-(p-methoxyphenylazo)-5-pyrazolone have been synthesized and were characterized by elemental and thermal analyses as well as by IR, UV-VIS, ¹HNMR, conductometric and magnetic measurements. The first stage in the thermal decomposition process of these complexes shows the presence of water of hydration, the second denotes the removal of the coordinated water molecules. The final decomposition products were found to be the respective metal oxides. The data of the investigated complexes suggest octahedral geometry with respect to Co(II) 1:1, tetrahedral for Ni(II) 1:1and 2:3; square planar for Cu(II) 1:1 and 2:3; the complexes with no coordinated water molecules (2:3) Co(II) and Mn(II) complexes are tetrahedral. This revised version was published online in August 2006 with corrections to the Cover Date.     

Study on the nematicidal activity and chemical structure of NO bidentate Schiff base some metal complexes

A series of Co(II), Cu(II), Y(III), Zr(IV), La(III), and U(VI) complexes derived from 2-(2-hydroxybenzylidinemine)-benzoic acid (L) ligand were synthesized. The mode of bonding of L and the structure of its metal complexes were investigated using different analytical and spectral tools (FT-IR, UV–Vis, ¹H NMR, mass, and XRD). The ligand chelated with the metal ions as a neutral bidentate through oxygen and azomethine nitrogen atoms. All metal complexes adopted octahedral geometry with characteristic color for metal ions. The results of magnetic moment measurements supported paramagnetic for some complexes (Co(II) and Cu(II)) and diamagnetic phenomena for the other complexes. The thermal decomposition of the ligand along with its metal complexes was explained. The molar conductance values of all complexes in (DMF) were found in the range 154.50 to 250.20 S cm² mol⁻¹ at room temperature. The activation thermodynamic parameters, such as E*, ΔH*, ΔS* and ΔG*, were calculated from the DTG curves using Coats–Redfern (CR) and Horowitz–Metzeger (HM) methods at n = 1 or n ≠ 1. The nematicidal activity of the synthesized L and their metal complexes was screened.     

Thermoanalytical investigations of 4-methylpiperazine-1-carbodithioic acid ligand and its iron(III), cobalt(II), copper(II) and zinc(II) complexes

The thermal decomposition studies on 4-methylpiperazine-1-carbodithioic acid ligand (4-MPipzcdtH) and its complexes, viz. [M(4-MPipzcdtH)_n](ClO4)_n (M=Fe(III) when n=3; M=Co(II), Cu(II) when n=2) and [Zn(4-MPipzcdtH)₂]Cl₂ have been carried out using non-isothermal techniques (TG and DTA). Initial decomposition temperatures (IDT), indicate that thermal stability is influenced by the change of central metal ion. Free acid ligand exhibits single stage decomposition with a sharp DTA endotherm. Complexes, [M(4-MPipzcdtH)_n](ClO₄)_n undergo single stage decomposition with detonation and give rise to very sharp exothermic DTA curves while the complex [Zn(4-MPipzcdtH)₂]Cl₂ shows three-stage decomposition patterns. The kinetic and thermodynamic parameters, viz. the energy of activation E, the frequency factor A, entropy of activation S and specific rate constant k, etc. have been evaluated from TG data using Coats and Redfern equation. Based upon the results of the differential thermal analysis study, the [M(4-MPipzcdtH)_n](ClO₄)_n complexes have been found to possess characteristic of high energy materials.     

Synthesis and characterization of cerium,thorium, and uranyl complexes with ( E )-4-(4-methoxyphenoxy)-4- oxobut-2-enoic acid

(E)-4-(4-Methoxyphenoxy)-4-oxobut-2-enoic acid and its Ce(IV), Th(IV), and UO₂(II) complexes were synthesized and characterized by MS, elemental analysis, IR, UV, TG-DTA, and NMR. The complexes have composition [CeL₂(OH)₂ · 2H₂O] · H₂O, [ThL₂(OH)₂ · 2H₂O] · H₂O, and [UO₂L₂ · 2H₂O] · H₂O. Molar conductance data confirm that the three complexes are nonelectrolytes. The IR and NMR results show that the carboxylates coordinate to the metal ions bidentate, and the ester carboxylic groups do not take part in coordination. Luminescence spectra of the ligand and complexes in DMSO at room temperature were also studied showing strong luminescence of the metal ions.     

Synthesis, characterization and thermal behavior of 1,1-dialkyl-3-(4-(3,3-dialkylthioureidocarbonyl)-benzoyl)thiourea and its Cu(II), Ni(II), and Co(II) complexes

We report the synthesis, characterization, and thermal behavior of 1,1-diethyl-3-(4-(3,3-diethylthioureidocarbonyl)benzoyl)thiourea, 1,1-di-n-propyl-3-(4-(3,3-di-n-propylthioureido carbonyl)benzoyl)thiourea and 1,1-di-n-butyl-3-(4-(3,3-di-n-butylthioureidocarbonyl)benzoyl)thiourea and their Ni(II), Cu(II), and Co(II) complexes. The structure of the prepared compounds was determined by elemental analysis, FT-IR, ¹H NMR spectroscopy and mass spectrometry. The ligands are coordinated to metal atoms in a bidentate manner yielding an essentially neutral complex of the type M₃L₃. Thermal decomposition of related compounds was investigated by DTA and TG techniques. The pyrolytic end product was identified by X-ray powder diffraction method. The text was submitted by the authors in English.     

Synthesis,characterization, and biological activity of some transition metal complexes with Schiff base ligands derived from 4-amino-5-phenyl-4<Emphasis Type="Italic">H</Emphasis>-1,2,4-triazole-3-thiol and salicaldehyde

Abstract  

The coordination behaviour of a Schiff base with SNO donation sites, derived from condensation of 4-amino-5-phenyl-4H-1,2,4-triazole-3-thiol and salicaldehyde, towards some bi- and trivalent metal ions, namely Cr(III), Mn(II), Fe(III), Co(II) (Cl, ClO₄), Ni(II) (Cl, ClO₄), Cu(II), and Zn(II), is reported. The metal complexes were characterized on the basis of elemental analysis, IR, ¹H NMR, solid reflectance, magnetic moment, molar conductance, and thermal analyses (TG, DTG, and DTA). The ionization constant of the Schiff base under investigation and the stability constants of its metal chelates were calculated pH-metrically at 25 °C and ionic strength μ = 0.1 M in 50% (v/v) ethanol–water mixture. The chelates were found to have octahedral (Mn(II)), trigonal bipyramidal (Co(II), Ni(II), Zn(II)), and tetrahedral (Cr(III), Fe(III), and Cu(II)) structures. The ligand and its binary chelates were subjected to thermal analyses and the different thermodynamic activation parameters were calculated from their corresponding DTG curves to throw more light on the nature of changes accompanying the thermal decomposition process of these compounds. The free Schiff base ligand and its metal complexes were tested in vitro against Aspergillus flavus, Candida albicans, C. tropicalis, and A. niger fungi and Bacillus subtilis and Escherichia coli bacteria in order to assess their antimicrobial potential. The results indicate that the ligand and its metal complexes possess antimicrobial properties.     

Synthesis and characterization of polymeric Ni(II) complexes of 4-(4-aminobenzyl)benzenamine (abba) and 4-(4-aminophenylthio)benzenamine (aptba) with thiocyanate

Two one-dimensional complexes, [Ni(SCN)₂(abba)₂] _n (abba?=?4-(4-aminobenzyl)benzenamine) (1) and [Ni(SCN)₂(aptba)₂] _n (aptba?=?4-(4-aminophenylthio)benzenamine) (2), were synthesized and characterized by EA, IR, X-ray crystallography and thermal analysis. The single crystal X-ray structural analyses of 1 and 2 show the complexes to be 1D chain polymers as a result of dibenzenamine (dba) bridging. Each Ni is six-coordinate and adopts a slightly distorted octahedral geometry with four N atoms from four dba ligands and two N atoms from two NCS-groups. Adjacent Ni atoms and two dba ligands form a 24-membered macrocycle. Thermogravimetric analysis and differential thermogravimetric analysis of 2 show that the thermal decomposition of 2 includes four transitions.     

Spectro-thermal characterization of chromium(III) and manganese(II) complexes with carboxyamide

Complexes of Cr(III) and Mn(II) with N′,N″-bis(3-carboxy-1-oxopropanyl) 2-amino-N-arylbenzamidine (H₂L¹) and N′,N″-bis(3-carboxy-1-oxophenelenyl) 2-amino-N-arylbenzamidine (H₂L²) have been synthesized and characterized by various physico-chemical techniques. The vibrational spectral data are in agreement with coordination of amide and carboxylate oxygen of the ligands with the metal ions. The electronic spectra indicate octahedral geometry around the metal ions, supported by magnetic susceptibility measurements. The thermal behavior of chromium(III) complexes shows that uncoordinated nitrate is removed in the first step, followed by two water molecules and then decomposition of the ligand; manganese(II) complexes show two waters removed in the first step, followed by removal of the ligand in subsequent steps. Kinetic and thermodynamic parameters were computed from the thermal data using Coats and Redfern method, which confirm first order kinetics. The thermal stability of metal complexes has been compared. X-ray powder diffraction determines the cell parameters of the complexes.     

Synthesis and characterization of lanthanide complexes prepared with 2-((E)-(1-hydroxy-2-methylpropan-2-ylimino)methyl)-6-methoxyphenol

Rare-earth complexes of the general formula [Ln(H₂L₁)₂(NO₃)₃] [Ln = Gd (1), Ho (2) or Nd (3)] were prepared from an o-vanillin derived Schiff base ligand, 2-((E)-(1-hydroxy-2-methylpropan-2-ylimino)methyl)-6-methoxyphenol (H₂L₁). The single-crystal X-ray diffraction studies and SHAPE analyses of the Gd(III) and Ho(III) complexes show that the complexes are ten-coordinate and exhibit distorted tetradecahedron geometries. The phenolate oxygen-bridged dinuclear complex, [Ce₂(H₂L₁)(ovan)₃(NO₃)₃] (4, ovan = monodeprotonated o-vanillin), was obtained from the reaction of Ce(NO₃)₃?6H₂O with H₂L₁. X-ray analysis revealed that hydrolysis of H₂L₁ occurred to yield o-vanillin, which bridged two cerium atoms with the Ce?Ce distance equal to 3.8232(6) Å. The Ce(III) ions are both ten-coordinate, but have different coordination environments, showing tetradecahedron and staggered dodecahedron geometries, respectively. With proton migration occurring from the phenol group to the imine function, complexation of the lanthanides to the ligand gives the Schiff base a zwitterionic phenoxo-iminium form.