Manganese(II), cobalt(II) and nickel(II) complexes with 2-phenyl-3-(benzylamino)-1,2-dihydroquinazolin-4(3H)-one,pseudohalides and some bidentate N-donor ligands

Some mixed ligand complexes of the type [M(L)(en or phen)(X)₂]; where M = Mn(II), Co(II) or Ni(II); L = 2-phenyl-3-(benzylamino)-1,2-dihydroquinazolin-4(3H)-one; en = ethylenediamine, phen = 1,10-phenanthroline; X = N₃ ⁻ or NCS⁻ have been prepared. All the complexes were characterized by physico-chemical, spectroscopic and thermal studies. On the basis of electronic spectra and magnetic susceptibility measurements, an octahedral geometry has been proposed for all the complexes. The phen complexes are thermally more stable than the en complexes. The electrochemical behavior of the Ni(II) complexes showed that the complexes of phen are reduced at more positive potential compared to the corresponding en complexes.     

Thermochemical parameters of adducts of cadmium(II) halides with bidentate N- and O-ligands

The adducts [CdX₂(L-L)], where X = Cl, Br, I; L-L = 2,2’-bipyridine (bipy) or 2,2′-bipyridine N,N′-dioxide (bipyNO) have been synthesized and characterized by melting points, elemental analysis, thermal analysis, and IR spectroscopy. From calorimetric studies in solution, the standard enthalpies of formation of the adducts and several thermochemical parameters were determined. The mean standard enthalpies of the cadmium-nitrogen and cadmium-oxygen bonds have been estimated.     

Five‐coordinate dinuclar cobalt (II), copper (II), zinc (II) and cadmium (II) complexes with 4‐bromo‐N‐(2‐pyridinylmethylene)benzenamine: Synthesis,characterisation and methyl methacrylate polymerization

A series of late transition metal complexes, [(bpma)Co(μ – Cl)Cl] ₂ , [(bpma)Cu(μ – Cl)Cl] ₂ , [(bpma)Zn(μ – Cl)Cl] ₂ and [(bpma)Cd(μ – Br)Br] ₂ (where bpma is 4‐bromo‐N‐((pyridin‐2‐yl)methylene)benzenamine) have been synthesized and structurally characterized. The X‐ray structures of dimeric complexes [(bpma)M(μ – X)X] ₂ (M = Co, Cu and Zn, X = Cl; M = Cd, X = Br) showed a distorted 5‐coordinate trigonal bipyramidal geometry involving two nitrogen atoms of N,N‐bidentate ligand, two bridged and one terminal halogen atoms. The complex [(bpma)Cu(μ – Cl)Cl] ₂ revealed the highest catalytic activity for the polymerisation of methyl methacrylate in the presence of modified methylaluminoxane with an activity of 9.14 × 10⁴ g PMMA/mol·Cu·h at 60 °C and afforded syndiotactic poly (methylmethacrylate) (rr = 0.69).     

Thermal study of mononuclear Pd(II) complexes of the type [Pd(X)<Subscript>2</Subscript>(Rtu)(PPh<Subscript>3</Subscript>)] (X = Cl,SCN; Rtu = <Emphasis Type="Italic">N</Emphasis>-methylthiourea, <Emphasis Type="Italic">N</Emphasis>-phenylthiourea)

The synthesis, spectroscopic characterization, and thermal analysis of the compounds [Pd(X)₂(mtu)(PPh₃)] (X = Cl⁻ (1), SCN⁻ (2); mtu = N-methylthiourea; PPh₃ = triphenylphosphine) and [Pd(X)₂(phtu)(PPh₃)] (X = Cl⁻ (3), SCN⁻ (4); phtu = N-phenylthiourea) are described. The thermal decomposition of the compounds occurs in two, three, or four stages and the final decomposition products were identified as Pd⁰ by X-ray powder diffraction. The thermal stability order of the complexes is 4 > 3>2 > 1.     

Experimental and theoretical studies of Mn(II) and Co(II) metal complexes of a tridentate Schiff's base ligand and their biological activities

We have used the condensation method to synthesize 2-acetyl-5-methylsemicarbazone ligand. Manganese(II) and Cobalt(II) complexes having formula [ML₂]X₂ were synthesized where M = Mn(II) and Co(II), L = ligand, X = Cl⁻, CH₃COO⁻, NO₃⁻, ½SO₄²⁻. The characterization data suggests the octahedral geometry for all the synthesized complexes. Tridentate nature of the 2-acetyl-5-methylsemicarbazone ligand was revealed by IR studies. Molar conductance analysis suggested the electrolytic nature of the complexes. The theoretical study includes geometrical optimization, HOMO-LUMO energy gap, energetic parameters and dipole moment. These results also confirmed the tridentate nature of the ligand and the octahedral geometry of complexes. The molecular electrostatic potential (MEP) study suggested the reactive sites for an electrophilic or nucleophilic attack in the ligand. We tested the synthesized compounds for their antifungal and antibacterial action via well diffusion method and found that parent ligand after the coordination with the metal ion showed more effective inhibition against bacteria and fungi.     

Synthesis,biological and physicochemical properties of Zinc(II) salicylate and 5-chlorosalicylate complexes with theophylline and urea

New zinc(II) salicylate complex compounds of general formula (X-C₆H₃-2-(OH)COO)₂Zn · L_n · xH₂O (where X = H, 5-Cl; L = theophylline, urea; n = 2, 4; x = 1, 2, 4) were prepared and their thermal, spectral and biological properties were studied. It was found that the thermal decomposition of hydrated compounds starts with the release of water. During the thermal decomposition of anhydrous compounds, the release of salicylic acid, theophylline, urea, CO₂, H₂O and C₆H₅Cl takes place. Zinc oxide was found as the final product of the thermal decomposition heated up to 900 °C. The complexes were tested against bacteria, yeasts and filamentous fungi. The highest biological activity show 5-chlorosalicylate compounds.     

Thermal stability and degradation of Co(II), Cd(II), and Zn(II) complexes with <Emphasis Type="Italic">N</Emphasis>-benzyloxycarbonylglycinato ligand

Thermal behavior of Co(II), Cd(II), and Zn(II) complexes with N-benzyloxycarbonylglycinato ligand was investigated using the results of TG, DSC and DTG analysis obtained at different heating rates (2.5 to 30 °C min⁻¹), from room temperature to about 900 °C. Mechanisms of complex degradation, as well as enthalpies of the degradation processes were determined. It is shown that thermal stability of investigated complexes correlates with their crystal structures, especially with the presence of crystallization and coordinated water molecules. The values of dehydration enthalpies are discussed and correlated with composition of the complexes. Kissinger’s, Ozawa’s, and Friedman’s isoconversion methods were used for the determination of kinetic parameters: the pre-exponential factor A and the apparent activation energy E _a. For all three complexes and all steps of degradation, the values of kinetics parameters obtained by Kissinger’s and Ozawa’s methods are in good agreement. The results obtained by Friedman’s method showed that some decomposition steps are simple and some others are complex ones.     

Thermal decomposition and antimicrobial activity of zinc(II) 2-bromobenzoates with organic ligands

New zinc(II) 2-bromobenzoate complex compounds with general formula Zn(2-BrC₆H₄COO)₂·nL·xH₂O (where L = urea, nicotinamide, N-methylnicotinamide, N,N-diethylnicotinamide, isonicotinamide, phenazone n = 0–2, x = 0–2) were prepared and characterized by elemental analysis, IR spectroscopy and thermal analysis. The thermal decomposition of hydrated compounds started with dehydration process. During the thermal decomposition organic ligand, carbon dioxide and bis(2-bromophenyl)ketone were evolved. The solid intermediates and volatile products of thermal decomposition were proved by IR spectroscopy and mass spectrometry. The final solid product of the thermal decomposition heated up to 1073 K was zinc oxide. Antimicrobial activity of the prepared compounds was tested against various strains of bacteria, yeasts and filamentous fungi (E. coli, S. aureus, C. albicans, R. oryzae, A. alternate and M. gypseum). It was found that the selected bacteria were more sensitive to the studied zinc(II) complex compounds than the yeast and the filamentous fungi.     

Synthesis,spectroscopic, thermal and biological aspect of mixed ligand copper(II) complexes

Derivative of 8-hydroxyquinoline i.e. Clioquinol is well known for its antibiotic properties, drug design and coordinating ability towards metal ion such as Copper(II). The structure of mixed ligand complexes has been investigated using spectral, elemental and thermal analysis. In vitro anti microbial activity against four bacterial species were performed i.e. Escherichia coli, Pseudomonas aeruginosa, Serratia marcescens, Bacillus substilis and found that synthesized complexes (15–37 mm) were found to be significant potent compared to standard drugs (clioquinol i.e. 10–26 mm), parental ligands and metal salts employed for complexation. The kinetic parameters such as order of reaction (n = 0.96–1.49), and the energy of activation (E _a = 3.065–142.9 kJ mol⁻¹), have been calculated using Freeman–Carroll method. The range found for the pre-exponential factor (A), the activation entropy (S* = −91.03 to−102.6 JK⁻¹ mol⁻¹), the activation enthalpy (H* = 0.380–135.15 kJ mol⁻¹), and the free energy (G* = 33.52–222.4 kJ mol⁻¹) of activation reveals that the complexes are more stable. Order of stability of complexes were found to be [Cu(A⁴)(CQ)OH] · 4H₂O > [Cu(A³)(CQ)OH] · 5H₂O > [Cu(A¹)(CQ)OH] · H₂O > [Cu(A²)(CQ)OH] · 3H₂O     

Tricarbonylrhenium(I) and -technetium(I) complexes with bis(2-pyridyl)phenylphosphine and tris(2-pyridyl)phosphine

(NEt₄)₂[Re(CO)₃Br₃] or (NEt₄)₂[Tc(CO)₃Cl₃] react with bis(2-pyridyl)phenylphosphine (PPhpy₂) or tris(2-pyridyl)phosphine (Ppy₃) under formation of neutral tricarbonyl complexes of the composition [M(CO)₃X(L)] (M = Re, X = Br; M = Tc, X = Cl; L = PPhpy₂ or Ppy₃). In all isolated products, the ligands coordinate solely via two of their nitrogen atoms. All attempts to force a tripodal coordination of the phosphinopyridines failed. Removal of the bromo ligands from (NEt₄)₂[Re(CO)₃Br₃] by the addition of AgNO₃ in THF/water, and subsequent reaction of the resulting [Re(CO)₃(THF)₃](NO₃)with Ppy₃ yielded the complex [Re(CO)₃(NO₃)(Ppy₃-N,N′)] with a monodentate coordinated nitrato ligand. The products have been characterized spectroscopically and by X-ray structure analyses.     

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).     

New complexes of Mn(II), Co(II), Ni(II) AND Cu(II) with 2,2’- OR 2,4’-bipyridine and formates (Synthesis, thermal and other properties)

New mixed-ligand complexes with empirical formulae: Mn(2-bpy)_1.5L₂·2H₂O, M(2-bpy)₂L₂·3H₂O (M(II)=Co, Cu), Ni(2-bpy)₃L₂·4H₂O and M(2,4’-bpy)₂L₂·2H₂O (where 2-bpy=2,2’-bipyridine, 2,4’-bpy=2,4’-bipyridine; L=HCOO^– ) have been obtained in pure solid-state. The complexes were characterized by chemical and elemental analysis, IR and VIS spectroscopy, conductivity (in methanol and dimethylsulfoxide). The way of metal-ligand coordination discussed. The formate and 2,4’-bpy act as monodentate ligands and 2-bpy as chelate ligand. The new complexes with ligand isomerism were identified. During heating the complexes lose water molecules in one or two steps. Thermal decomposition after dehydration is multistage and yields corresponding metal oxides as final products. A coupled TG-MS system was used to analysis principal volatile thermal decomposition (or fragmentation) products of Ni(2,4’-bpy)₂(HCOO)₂·2H₂O under dynamic air or argon atmosphere.     

Synthesis, characterization, and crystal structure of two zinc(II) halide complexes with the symmetrical bidentate Schiff-base ligand (3,4-MeO-ba)2en

Abstract  

In this study two zinc(II) halide complexes with the Schiff-base ligand (3,4-MeO-ba)₂en [N,N′-bis(3,4-dimethoxybenzylidene)ethane-1,2-diamine] have been synthesized and characterized by elemental analyses (CHN), single-crystal X-ray diffraction, Fourier-transform infrared (FT-IR), and ¹H nuclear magnetic resonance (NMR) spectroscopy. The metal-to-ligand ratio was found to be 1:1 within the formula ZnX₂((3,4-MeO-ba)₂en) (X = Br, I). Crystal structure analysis reveals that the coordination geometry around the zinc(II) ions in the two isotypic complexes is distorted tetrahedral. The Schiff-base ligand (3,4-MeO-ba)₂en acts as a chelating ligand and coordinates via two N atoms to the metal center and adopts an (E,E) conformation. The coordination spheres of the metal atoms are completed by the two halide atoms, which are also involved in weak non-classical hydrogen-bonding interactions of the type C–H···X–Zn.     

Nickel(II) and copper(II) complexes with an asymmetric bidentate Schiff-base ligand derived from furfurylamine

New asymmetric bidentate Schiff-base ligand (5-bromo-2-hydroxybenzyl-2-furylmethyl)imine, (HL), and its nickel(II) and copper(II) complexes with the general composition ML₂ [M = Ni (1) and Cu (2)], were prepared. The ligand and the metal complexes were characterized by elemental analysis, FT-IR, and UV–Vis spectroscopy. In addition, ¹H-NMR and X-ray powder diffraction (XRD) were employed for characterization of ligand and metal complexes, respectively. Thermogravimetric analysis (TGA) of the ligand and metal complexes revealed the thermal stability and decomposition pattern of the species.     

Syntheses and spectrothermal studies of triethanolamine complexes of Co(II), Ni(II), Cu(II) and Cd(II) squarates

The triethanolamine complexes, [M(tea)₂]sq·nH₂O, (n=2 for Co(II), n=0 for Ni(II), Cu(II) and n=1 for Cd(II), tea=triethanolamine, sq²⁻=squarate), have been synthesized and characterized by elemental analyses, magnetic susceptibility and conductivity measurements, UV-Vis and IR spectra, and thermal analyses techniques (TG, DTG and DTA). The Co(II), Ni(II) and Cu(II) complexes possess octahedral geometry, while the Cd(II) complex is monocapped trigonal prismatic geometry. Dianionic squarate behaves as a counter ion in the complexes. The thermal decomposition of these complexes takes place in three stages: (i) dehydration, (ii) release of the tea ligands and (iii) burning of organic residue. On the basis of the first DTG_max of the decomposition, the thermal stability of the anhydrous complexes follows the order: Ni(II), 289°C>Co(II), 230°C>Cu(II), 226°C>Cu(II), 170°C in static air atmosphere. The final decomposition products — the respective metal oxides — were identified by FTIR spectroscopy.     

Luminescence and thermal behavior of copper (I) complexes with heterocyclic thiones. Part II: cationic complexes

Copper (I) halide complexes formulated as [(L)₂Cu(μ₂-L)₂Cu(L)₂]²⁺ 2Χ⁻, (X = Cl, Br and L = pyridine-2-thione (py2SH) or 4,6-dimethylpyrimidine-2-thione (dmpymtH)) were prepared, and their photoluminescence and thermal properties were investigated. The complexes are strongly emissive in the solid state, with the emissions being dominated by large Stokes shifts (>200 nm), which are depending on both the heterocyclic thione and the nature of the halogen. These emissions can be assigned to MLCT with some mixing of the halide-to-ligand (XL) CT characters. Simultaneous TG/DTG–DTA technique was used for two complexes with the dmpymtH ligand to determine their thermal degradation, which was found to be very complicated. In inert atmosphere the residues at 1,000 °C (verified with PXRD) were mainly Cu₂S, while at 1,300 °C a mixture of Cu₂S and Cu. In oxygen atmosphere the residues were CuO.     

Studies on Some Nickel(II) and Cobalt(II) Mixed Ligand Complexes of Arylsalicyl-Aldimine and Other Ligands

Several new mixed ligand complexes of Ni(II) and Co(II) of p-tolylsalicylaldimine (Sal-TH) or p-anisylsalicylaldimine (Sal-AH) with 8-hydroxyquinoline (HOx), benzohydroxamic acid (BH₂) or α-picoline (α-pic) have been synthesized. The complexes have the general formulae: [M(Sal-T)L],[M(Sal-A)L]⋅H₂O or [Ni(Sal-T)₂(α-pic)₂]⋅H₂O where M=Ni(II) or Co(II), Sal-T=p-tolylsalicylaldiminate, Sal-A=p-anisylsalicylaldiminate, L=8-hydroxyquinolinate or benzohydroxamate and α-pic=α-picoline. Analytical, conductivity and spectral data support a square planar structure for Co(II) complexes and octahedral structure for Ni(II) complexes. The thermal behaviour of the complexes has been studied by TG and DTG techniques. It was proposed that the decomposition of the complexed Schiff base takes place via a radical mechanism while for 8-hydroxyquinolinate or benzohydroxamate via proton transfer. Kinetic parameters of the thermal decomposition process have been computed by means of Coats-Redfern and Horowitz-Metzger methods. This revised version was published online in August 2006 with corrections to the Cover Date.     

Syntheses,structures, and properties of two mononuclear cobalt(III) azido complexes containing a tetradentate N-donor Schiff base as end-capping ligand

Two hexacoordinated mononuclear Co(III) compounds of the type cis-[Co(L)(N₃)₂] X [1, X = ClO₄; 2, X = PF₆; L = N,N′-(bis(pyridine-2-yl)benzylidine)-1,4-butanediamine] have been synthesized and characterized by physicochemical and spectroscopic methods. The crystal structures of complexes 1 and 2 both have distorted octahedral geometry with two terminal azides in mutual cis orientations. In the crystalline state, two mononuclear units of 1 are associated by weak C–H…π interactions to produce a dimeric unit, which packs through C–H…O hydrogen bonds and π…π interactions leading to a 2-D continuum. The mononuclear units in 2 are engaged in weak cooperative intermolecular C–H…π interactions and multiple C–H…F hydrogen bonds giving rise to a 3-D network structure. These diamagnetic compounds are redox active and show luminescence in DMF solutions.     

Chiral distinction in square planar Pt and Pd complexes of 2,2′-bipyridine derivatives

A computational study of square planar organometallic complexes formed by the ligand 2,2′-bipyridine and all its possible difluoro derivatives in analogous position of the aromatic rings (n,n′-difluoro-2,2′-bipyridine, where n = n′ = 3, 4, 5, and 6) and two M–X₂ (M = Pd and Pt and X = F, Cl, Br, and I) fragments has been carried out amounting to a total of 80 complexes. Relationships have been found between the chiral distinction energy and the different chemical moieties present. Using the statistical Free-Wilson method, the relative energies between the diastereomeric complexes have been correlated with the position of the substituent, the counter anion, and the central metal cation.     

Thermal behaviour and spectroscopic studies of complexes of some divalent transitional metals with 2-benzoil-pyridil-izonicotinoylhydrazone

New complexes of 2-benzoyl-pyridil-isonicotinoylhydrazone (L) with Cu(II), Co(II), Ni(II) and Mn(II), having formula of type [ML₂] SO₄·xH₂O (M = Cu²⁺, Co²⁺, Ni²⁺, x = 2 and M = Mn²⁺, x = 3), have been synthesised and characterised. All complexes were characterised on the basis of elemental analyses, IR spectroscopy, UV–VIS–NIR, EPR, as well as thermal analysis and determination of molar conductivity and magnetic moments. The thermal behaviour of complexes was studied using thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). The structure of L hydrazone was established by X-ray study on single crystal. The ligand works as tridentate NNO, being coordinated through the azomethine nitrogen, the pyridine nitrogen and carbonylic oxygen. Heats of decomposition, ΔH, associated with the exothermal effects were also determined.