Synthesis, characterization, solvatochromic behavior and crystal structures of complexes [CoIII(salophen)(thioacetamide)2]ClO4 and [CoIII(salophen)(thiobenzamide)2]ClO4

Two new cobalt(III) complexes of the Schiff base N,N′-disalicylidene-1,2-phenylendiimine dianion (salophen), trans- [Co^III(salophen)(ta)₂]ClO₄, (ta = thioacetamide) (1) and trans-[Co^III(salophen)(tb)₂]ClO₄, (tb = thiobenzamide) (2) were synthesized and characterized using single-crystal X-ray diffraction and spectroscopic techniques. Both complexes show solvatochromism in a variety of solvents. Complex (1) crystallized from CHCl₃ as a solvate of orthorhombic symmetry, space group Pca2₁ with a = 17.3480(10) Å, b = 18.7522(10) Å, c = 18.8128(11) Å, α = β = γ = 90°, and Z = 8. The cobalt(III) center lies in a distorted octahedral environment. The crystal structure of (1) consists of two independent [Co^III(salophen)(ta)₂]⁺ cations and ClO₄ ^- anions held together essentially via hydrogen bonds and π-π stacking interactions. Complex (2), forming also a CHCl₃ solvate, crystallized in the monoclinic space group P2₁/n with a = 14.710(3) Å, b = 13.506(3) Å, c = 18.595(4) Å, β = 100.295(4)°, and Z = 4. The geometry around cobalt(III) center is a distorted octahedron. The crystal structure of (2) contains a [Co^III(salophen)(tb)₂]⁺ complex with a remarkably twisted salophen ligand. Both complexes, (1) and (2), contain approximately one disordered CHCl₃ molecule per Co in the solid state.     

Synthesis and spectroscopic characterization of [CoIII(salophen)(amine)2]ClO4 (amine=morpholine,pyrrolidine, and piperidine) complexes. The crystal structures of [CoIII(salophen)(morpholine)2]ClO4 and [CoIII(salophen)(pyrrolidine)2]ClO4

Three Co(III) complexes of the type [Co(salophen)(amine)₂]ClO₄, salophen=N,N′-disalicylidene-1,2-phenylendiamine dianion and amine=morpholine (1), pyrrolidine (2), and piperidine (3), have been synthesized and characterized by elemental analysis, IR, UV–Vis, ¹H, and ¹³C NMR spectroscopy. [Co(salophen)(morpholine)₂]ClO₄ (1) and [Co(salophen)(pyrrolidine)₂]ClO₄ (2) have been studied by X-ray diffraction. Compound 1 crystallizes in ribbons of complexes and perchlorates held together by weak NH⋯O and CH⋯O hydrogen bonds between morpholines and perchlorates. The latter also interconnect the chains to a 3D network. Some minor π–π interactions exist. Compound 2 crystallizes as endless chains of complexes linked by weak CH⋯O hydrogen bonds to the disordered perchlorates. The pyrrolidine moiety is turned by 90° with respect to 1 and forms intramolecular NH⋯O hydrogen bonds. The coordination polyhedra of 1 and 2 possess C_s symmetry, and the salophens are not planar in either of them.     

Synthesis, characterization and spectral investigation of salen-type cobalt(iii) schiff base complexes. x-ray crystal structure of trans-[Co(Me-Salen)(3-Acetylpyridine)2]ClO4

Two new cobalt(III) complexes of the Schiff base N,N??-bis(methylsalicylidene)-1,2-ethylenediimine dianion (Me-Salen), trans-[Co(Me-Salen)(L)₂]ClO₄ (L = 3-acetylpyridine) (I) and (L = 4-acetylpyridine) (II), have been synthesized and characterized by elemental analyses, FT-IR, UV-Vis, and ¹H NMR spectroscopy. The X-ray diffraction analysis reveals that I crystallizes in the monoclinic space group P2₁/c and displays a distorted octahedral coordination geometry about Co with the equatorial plane formed by the N₂O₂ donors of the tetradentate Schiff base dianion, the two phenolate O atoms and the two imine N atoms of which are each mutually in cis-position. Two 3-acetylpyridine molecules are attached to the metal atom to fill its axial positions.     

Spectroscopic studies,structural characterization and electrochemical studies of two cobalt (III) complexes with tridentate hydrazone Schiff base ligands: Evaluation of antibacterial activities,DNA‐binding,BSA interaction and molecular docking

Co(III) complexes of tridentate Schiff base ligands derived from N‐(2‐hydroxybenzylideneamino)benzamide (H ₂ L ¹ ) and 2‐(2‐hydroxybenzylidene)hydrazine‐1‐carboxamide ( H ₂ L ² ) were synthesized and characterized using IR, Raman, ¹H–NMR and UV–Vis spectroscopies. X‐ray single crystal structures of complexes 1 and 2 have also been determined, and it was indicated that these Co(III) complexes are in a distorted octahedral geometry. The cyclic voltammetry (CV) of the complexes indicates an irreversible redox behavior for both complexes 1 and 2 . The antibacterial effects of the synthesized compounds have been tested by minimum inhibitory concentration and minimum bactericidal concentration methods, which suggested that the metal complexes exhibit better antibacterial effects than the ligands against Gram‐positive bacteria. The effects of the drug (drug  =  ligands and complexes) on bovine serum albumin (BSA) were examined using circular dichroism (CD) spectropolarimetry, and it was revealed that the BSA (BSA, as a carrier protein) secondary structure changed in the presence of the drug. Interaction of the drug with calf‐thymus DNA (CT‐DNA) was investigated by UV–Vis absorption, fluorescence emission, CV and CD spectroscopy. Binding constants were determined using UV–Vis absorption. The results indicated that the studied Schiff bases bind to DNA, with the hyperchromic effect and non‐intercalative mode in which the metal complexes are more effective than ligands. Furthermore, molecular docking simulation was used to obtain the energetic and binding sites for the interaction of the complexes with Mycobacterium tuberculosis enoyl‐acyl carrier protein reductase (InhA), and results showed that complex 1 has more binding energy.     

Synthesis and characterization of zinc(II) and cobalt(III) Schiff base complexes

Two mononuclear complexes with the Schiff base ligand 2-((2-(dimethylamino)ethylimino)methyl)phenol (HL), namely ZnL₂ and CoL₂(N₃), have been synthesized and characterized using single-crystal X-ray diffraction and spectroscopy (IR, ¹H NMR, UV–Vis, MS and EA). Both complexes are mononuclear. The coordination geometry in the Zn(II) complex is distorted square-pyramidal with a weak Zn···N interaction. The Co(III) complex is distorted octahedral, and the neutral molecule unit [Co^IIIL₂(N₃)] is connected by C–H···N hydrogen bonds to form a one-dimensional infinite chain. The luminescence of the zinc compound has been investigated. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Metallosurfactant Schiff base cobalt(III) coordination complexes. Synthesis,characterization, determination of CMC values and biological activities

Twelve surfactant Schiff base ligands were synthesized from salicylaldehyde and its chloro-, bromo- and methoxy- derivatives by condensation with long-chain aliphatic primary amines, and a number of mixed ligand cobalt(III) surfactant Schiff base coordination complexes of the type [Co(trien)A]²⁺ were synthesized from the corresponding dihalogeno complexes by ligand substitution. The Schiff bases and their complexes were characterized by physico-chemical and spectroscopic methods. The complexes form foams in aqueous solution upon shaking. The critical micelle concentration (CMC) values of the complexes in aqueous solution were obtained from conductance measurements. Specific conductivity data (at 303–323 K) served for the evaluation of the thermodynamics of micellization ( \Updelta G_\textm⁰ \Updelta G_{\text{m}}^{0} , \Updelta H_\textm⁰ \Updelta H_{\text{m}}^{0} , \Updelta S_\textm⁰ \Updelta S_{\text{m}}^{0} ). The complexes were tested for its antimicrobial activity.     

Synthesis,crystal structures,spectroscopic studies and antibacterial properties of a series of mononuclear cobalt(III) Schiff base complexes

New complexes of cobalt(III) with the tridentate and tetradentate Schiff base ligands: 3-methoxy-2-{(Z)[(2-hydroxyphenyl)imino]methyl}phenol (H₂L¹), 4-[(2-hydroxyphenyl)imino]-2-pentanone (H₂L²); and 2-((E)-1-(2-((E)-1-(2-hydroxy-4,5-dimethylphenyl)ethylideneamino)ethylimino)ethyl)-4,5 dimethylphenol (H₂L³), namely [Co^III(L¹)(N-MeIm)₃]PF₆ (1), [Co^III(L¹)(py)₃]ClO₄ (2), [Co(L¹)(py)₃][Co(L¹)₂] (3) and [Co^III(L²)(N-MeIm)₃]PF₆ (4) and [Co(L³)(N-MeIm)₂]PF₆ (5), were synthesized and characterized by physico-chemical and spectroscopic methods. The crystal structures of the complexes were determined by X-ray crystallography. In each of these complexes, the cobalt(III) centre has a slightly distorted octahedral environment, utilizing all available coordination centres of the ligands. The complexes were also screened for in vitro antibacterial activities against four human pathogenic bacteria, and their minimum inhibitory concentrations indicated good antibacterial activities.     

Synthesis,structural characterisation and electrochemical and antibacterial studies of Schiff base copper complexes

Neutral complexes of Cu^II have been synthesised from the Schiff bases derived from salicylidene-4-aminoantipyrine and PhNH₂/substituted anilines. The structural features have been determined from their microanalytical, i.r., u.v.–vis., ¹H-, ¹³C-n.m.r., mass and e.s.r. spectral data. All the complexes exhibit square-planar geometry. Their magnetic susceptibility measurements and low conductance data provide evidence for the monomeric and non-electrolytic natures of the complexes respectively. The electrochemical behaviour of the complexes in MeCN at 298 K was studied. The kinetic parameters were determined and are discussed. The X-band e.s.r. spectra of the complexes in DMSO at 300 and 77 K were recorded and their salient features are reported. The powder XRD diffraction patterns for all the complexes are found to be similar. The antimicrobial activity of the ligands and their copper complexes against the bacteria Staphylococcus aureus, Klebsiella pneumoniae, Salmonella typhi, Pseudomonas aerugenosa and Bacillus subtilis are also reported. The complexes have higher activities than those of the free Schiff bases. Moreover, they have higher activity than the control (ampicillin) except for Klebsiella pneumoniae and Pseudomonas aerugenosa.     

Synthesis,characterization and electrochemical properties of copper(II) complexes derived from succinoyldihydrazine Schiff base ligands

Four new copper(II) complexes of the composition [Cu(H₂L)(H₂O)] have been synthesized by template method from reaction of copper(II) acetate, succinoyldihydrazine and some o-hydroxy aromatic aldehydes and ketones in aqueous methanol media. The composition of the complexes has been established on the basis of data obtained from analytical and mass spectral studies. The structure of the complexes has been discussed in the light of molar conductance, magnetic moment, Uv-vis, EPR and IR spectral studies. All of the complexes are non-electrolyte in DMSO. The μ_eff values for the complexes fall in the region 1.76–1.85 BM which rules out the possibility of any M–M interaction in the structural unit of the complexes. The ligands coordinate to the metal centre in enol form through phenolate/naphtholate oxygen atoms and azomethine nitrogen atoms. The NMR spectra show that ligands are present in anti-cis configuration in uncoordinated state. In all of the complexes the copper centre adopts square pyramidal stereochemistry. The unpaired electron is present in $d_{x^2-y^2}$ orbital in the ground state for copper centre in the complexes. The electron transfer reactions for the complexes have been studied by cyclic voltammetry.     

Synthetic aspects, crystal structures and antibacterial activities of manganese(III) and cobalt(III) complexes containing a tetradentate Schiff base

Three new Schiff base complexes, namely [Mn(L)Cl] · H₂O (1), [Co(L)Cl]₂ · 2CH₃COCH₃ (2) and [Co(L)NCS]₂ (3), where H₂L = 2,2′-[propane-1,2-diylbis(nitriloeth-1-yl-1-ylidene)]diphenol, have been prepared and characterized. The syntheses of 1 and 2 have been achieved by reacting equimolar amounts of the respective metal chloride and the tetradentate Schiff base ligand (H₂L). While the mononuclear Mn(III) complex 1 was obtained with MnCl₂ in acetone medium, the same synthetic system yielded the binuclear Co(III) complex 2 in the presence of CoCl₂. Dissolution of 1 and 2 followed by crystallization with ammonium thiocyanate in methanol yielded two isostructural phenoxo-bridged binuclear complexes, namely [Mn(L)NCS]₂ (previously reported by us) and a new complex [Co(L)NCS]₂ (3), respectively. All the complexes 1–3 have been characterized by microanalytical, spectroscopic, single crystal X-ray diffraction and other physicochemical studies. Structural studies reveal that 1 adopts a distorted tetragonal pyramidal geometry while 2 and 3 comprise dimeric Co(III) units with bridging phenolate oxygen atoms. All the complex units in 1–3 and the respective solvent molecules are held together by weak intermolecular H-bonding to constitute a supramolecular network in the solid state. The antibacterial activity of the complexes has been tested against some Gram(+) and Gram(?) bacteria.     

Synthesis,spectral, electrochemical and catalytic studies of new Ru(III) tetradentate Schiff base complexes

The synthesis and characterization of several hexa‐coordinated ruthenium(III) Schiff base complexes of the type [RuX(EPh₃)(L)] (X = Cl or Br; E = P or As; L = dianion of the tetradentate Schiff base) are reported. IR, EPR, electronic spectra and cyclic voltammetric data of the complexes are discussed. An octahedral geometry has been tentatively proposed for all of these complexes. The new complexes have been subjected to catalytic activity in the reaction of oxidation of alcohols in the presence of N‐methylmorpholine‐N‐oxide. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis, physical and electrochemical characterization of mono- and heterobinuclear m-functionalized iron(III) Schiff base complexes

Mo(NO)T _p ^* Cl₂ (T _p ^* ?=?3,5-dimethyl pyrazole) when reacted with m-functionalized Fe(III) Schiff base complexes; the Schiff base ligands being derived from condensation of 2,4-dihydroxybenzaldehyde or salicylaldehyde with a variety of ??,??-diamines [1,2-C₆H₄(NH₂)₂, NH₂(CH₂) _n NH₂; n?=?2?C4] affords bimetallic complexes containing two potential reduction centers. The compounds were characterized by physicochemical and spectroscopic methods. It is shown that as the polymethylene carbon chain of the Schiff base backbone increases, the physicochemical and spectroscopic properties also change gradually. Electrochemical data show that the m-functionalized complexes reduce at potentials less cathodic than their p-substituted analogues. It is also shown that the redox potentials are solvent dependent.     

Synthesis,crystal structure,and antimicrobial activity of a series of cobalt(III) Schiff base complexes

Abstract

A series of six new mononuclear Schiff base complexes, 1–6 of cobalt(III) of the general formula, [CoLX] or its adduct with methanol, is reported. The pentadentate Schiff base ligand (H₂L) was obtained by the condensation of N-(3-aminopropyl)-N-methylpropane-1,3-diamine with 1-(2-hydroxyphenyl)ethanone (H₂L¹) or 1-(2-hydroxyphenyl)propan-1-one (H₂L²). X stands for the pseudohalides, N₃^–, N(CN)₂^? , and NCS^–. The complexes have been synthesized by the reaction of equimolar amounts of cobalt(II) nitrate with H₂L¹ or H₂L² in the presence of the respective pseudohalide in methanol medium. All the complexes have been characterized by microanalytical, spectroscopic, single crystal XRD (except 3), and other physicochemical studies. Structural studies reveal that the central Co(III) ion in 1, 2, 4, 5, and 6 adopts a distorted octahedral geometry with a CoN₄O₂ chromophore. Weak intermolecular H-bonding and/or π-interactions are operative in these complexes to bind the molecular units. The antimicrobial activity of all the complexes and their constituent Schiff bases has been tested against some common bacteria and fungi.     

Synthesis and characterization of titanium (IV) Schiff base complexes,part III1. Octahedral titanium (IV) complexes of some dibasic terdentate Schiff base ligands

Summary Complexes of the X₂Ti(SB) type, where X is OMe, OEt and OPr-i and SB is the dianion of salicylaldehyde-2-hydroxyanil (H₂SAP), acetylacetone-2-hydroxyanil (H₂AAP) and acetylacetone-2-mercaptoanil (H₂ASP), have been prepared and characterized by means of conductivity, molecular weight, i.r., n.m.r and mass spectral measurements. The ONO and ONS donor ligands are terdentate and the titanium(IV) atom attains six-coordinationvia dimerization of the complexes. The tendency of (i-PrO)₂Ti(AAP), where AAP is the dianion of acetylacetone-2-hydroxyanil, to become monomeric and to disproportionate to Ti(AAP)₂ and Ti(OPr-i)₄ was also investigated. Spectral data are also presented for the octahedral complexes of the Ti(SB)₂ type, where SB is the dianion of H₂SAP, H₂AAP, H₂ASP or of the related ONO donor ligands salicylaldehyde-2-hydroxyethylimine (H₂SAE), salicylaldehyde-3-hydroxypropylimine (H₂SPA), and diisopropylethanolamine (H₂DIP).Presented in part at the 166th ACS National Meeting, Chicago, Illinois, Aug. 26–31, 1973; No. INORG. 50.     

Syntheses,crystal structures and antibacterial activities of azido-bridged cobalt(III) complexes with Schiff bases

Two end-on azido-bridged Co(III) complexes, [Co₃(L1)₂(μ_1,1-N₃)₄(N₃)₂(OH₂)(OCH₂CH₃)]·0.5H₂O (1) and [Co₂(L2)₂(μ_1,1-N₃)₂(N₃)₂] (2), where L1 and L2 are the deprotonated form of 5-methoxy-2-[(2-morpholin-4-ylethylimino)methyl]phenol and 2-ethoxy-6-[(2-isopropylaminoethylimino)methyl]phenol, respectively, were prepared and structurally characterized by physicochemical and spectroscopic methods and single crystal X-ray determination. Complex (1) is a trinuclear Co compound, while complex (2) is a centrosymmetric dinuclear Co compound. In both complexes, the Co atoms are in octahedral coordination. The preliminary biological tests show that the complexes have excellent antibacterial activity.     

Synthesis,structure and antibacterial activity of manganese(III) complexes of a Schiff base derived from furfurylamine

Two new mononuclear complexes of manganese(III) viz. [MnL₂(LH)₂]ClO₄ (1) and [MnL₂(N₃)]·0.5CH₃OH (2) have been synthesized by reacting manganese perchlorate with furfurylamine and salicylaldehyde (plus sodium azide in 2) where L = (2-hydroxybenzyl-2-furylmethyl)imine, an asymmetric bidentate Schiff base formed in situ to bind the Mn(III) ion. The complexes have been characterized by elemental analysis, IR spectroscopy, TGA and single crystal X-ray diffraction studies. Structural studies reveal that the complexes 1 and 2 adopt an octahedral and a square pyramidal geometry, respectively. The antibacterial activity of the complexes has been tested against Gram(+) and Gram(?) bacteria.     

Synthesis,crystal structures,and antibacterial studies of silver(I) complexes with reduced Schiff base amino acid ligands

Three Ag(I) complexes of reduced Schiff base amino acid ligands, [Ag₂(Hshis)₂]·3H₂O (1), Ag(Hcgly) (2), and Ag(cala) (3) (H₂shis = N-(2-hydroxybenzyl)-l-histidine, H₂cgly = N-(2-hydroxy-5-chlorobenzyl)-glycine, Hcala = N-(4-chlorobenzyl)-d,l-alanine), have been synthesized and characterized by X-ray crystallography. Complex 1 shows a dimeric structure, while complex 2 shows one-dimensional zigzag chains, which are extended into a two-dimensional supramolecular sheet by hydrogen bonds. Complex 3 exhibits a 2D sheet structure with dangling arms. The antimicrobial activities of the complexes have been investigated.     

Synthesis,spectroscopy, electrochemistry and structural determination of asymmetric cobalt(III) Schiff base complexes

The [CoL(PR₃)(CH₃OH)]ClO₄ (where L = MeSalophen, 5-NO₂MeSalophen, 5-BrMeSalophen, 5-MeOMeSalophen, 4-MeOMeSalophen, 3-MeOMeSalophen and R=Ph or Bu) complexes were synthesized and also characterized by FTIR, UV–Vis, ¹H NMR and ¹³C NMR spectroscopies. The absorptions between 550 and 750 nm for the complexes are attributed to d–d transitions. Electrochemical properties of the complexes were examined by means of cyclic voltammetry. The anodic peak potentials were more positive in the following trend NO₂ > Br > H > MeO and are in accordance with electronic effects of the substituents. The crystal structure of [Co(5-NO₂MeSalophen)(PBu₃)(CH₃OH)]ClO₄ and [Co(5-BrMeSalophen)(PPh₃)(CH₃OH)]ClO₄ was determined by single-crystal X-ray diffraction. They showed six-coordinated pseudo-octahedral geometries in which equatorial planes are formed by the O(1), O(2), N(1) and N(2) atoms of the Schiff base and the axial positions were occupied by PR₃ and methanol.     

Synthesis,characterization, electrochemical,catalytic and antimicrobial activity studies of hydrazone Schiff base ruthenium(II) complexes

Four tridentate O, N, O donor Schiff base ligands were prepared by the reaction of substituted benzhydrazide and appropriate salicylaldehyde. The complexes of these ligands were synthesized by refluxing the ligands with ruthenium(II) starting complexes of the formula [RuHCl(CO)(EPh₃)₂B] in benzene, where E = P or As; B = PPh₃ or AsPh₃ or pyridine. The newly synthesized complexes were characterized by elemental, spectral (FT‐IR, UV and NMR) and electrochemical data. On the basis of the above studies, an octahedral structure has been proposed for all the complexes. The catalytic efficiency of the complexes in aryl–aryl couplings and oxidation of alcohols was examined and their inhibition activity against the growth of the micro‐organisms was also examined. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis,characterization and electrochemical studies of ruthenium(III) heterocyclic Schiff bases

A series of hexacoordinated Ru^III–PPh₃ complexes of general formula [RuCl(PPh₃)L] (L = tetradentate Schiff bases derived from the condensation of 2-furaldehyde or thiophene-2-carboxyaldehyde with alkyl and aryl diamines have been synthesized. The complexes were characterized by elemental analyses, spectroscopic and cyclic voltammetric studies. All of the complexes were paramagnetic. Coordination of the Schiff base appears to occur through the two nitrogen and two heterocyclic oxygen/sulphur atoms.