The synthesis and characterization of 2,4,6-tris(3,4-dihydroxybenzimino)-1,3,5-triazine and its [salen/salophenFe(III)] and [salen/salophenCr(III)] capped complexes

Four new trinuclear Fe(III) and Cr(III) complexes involving tetradentate Schiff bases N,N′-bis(salicylidene)ethylenediamine-(salenH₂) or bis(salicylidene)-o-phenylenediamine-(salophenH₂) with 2,4,6-tris(3,4-dihydroxybenzimino)-1,3,5-triazine have been synthesized and characterized by means of elemental analysis, ¹H N.M.R., FT-IR spectroscopy, thermal analyses and magnetic susceptibility measurements. The complexes have also been characterized as low-spin distorted octahedral Fe(III) and Cr(III) bridged by catechol group.     

The synthesis and characterization of single substitute melamine cored Schiff bases and their [Fe(III) and Cr(III)] complexes

In this study, firstly, two single substitute novel ligands have been synthesized by reacting melamine with 3,4,-dihydroxybenzaldeyhde or 4-carboxybenzaldehyde. Then, eight new mono nuclear single substitute [Salen/Salophen Fe(III) and Cr(III)] complexes have been synthesized by reacting the ligands [2-(3,4-dihydroxybenzimino)-4,6-diamimo-1,3,5-triazine and 2-(4-carboxybenzimino)-4,6-diamimo-1,3,5-triazine)] with tetradentate Schiff bases N,N′-bis(salicylidene)ethylenediamine-(salenH₂) or bis(salicylidene)-o-phenylenediamine-(salophen H₂). And then, all ligands and complexes have been characterized by means of elementel analysis, FT-IR spectroscopy, ¹H NMR, LC–MS, thermal analyses and magnetic suscebtibility measurements. Finally, metal ratios of the prepared complexes were determined using AAS. The complexes have also been characterized as disorted octahedral low-spin Fe(III) and Cr(III) bridged by catechol and COO^? groups.     

The investigation of complexation properties and synthesis of the (salen and salophen)-bridged Fe/Cr(III) capped complexes of novel Schiff bases

This article describes synthesis of novel Schiff base and its complexation properties with Fe(III) and Cr(III). Firstly 1,3,5-tris (formylphenoxymethyl)benzene (1, TRIPOD) with tris aldehyde groups were synthesized using the 1,3,5-trisbromomethylbenzene and 4-hydroxybezaldehyde. The compound 1 was converted to the Schiff base derivative (2, TCPIM-TRIPOD) with p-aminobenzoic acid. The prepared TCPIM-TRIPOD were reacted with four new trinuclear Fe(III) and Cr(III) complexes involving tetradenta Schiff bases N,N-bis(salicylidene)ethylenediamine-(salenH₂) or bis(salicylidene)-o-phenylenediamine-(salophenH₂) and characterized by means of elemental analysis carrying out infrared spectroscopy (IR), thermogravimetric analysis (TG), nuclear magnetic resonance (¹H-NMR), elemental analysis and magnetic susceptibility measurement. The complexes can also be characterized as low-spin distorted octahedral Fe(III) and Cr(III) bridged by carboxylic acids. The tricarboxylic acids play a role as bridges for weak antiferromagnetic intramolecular exchange.     

Ortho-metallated ruthenium(III) complexes with some acid hydrazide based Schiff bases

Ortho-metallated ruthenium(III) complexes with Schiff bases (H₂L) derived from one mole equivalent each of benzaldehyde and acid hydrazides are described. Reactions of H₂L with [Ru(PPh₃)₃Cl₂] in presence of NEt₃ (1:1:2 mole ratio) under aerobic conditions in methanol provide the complexes having the general formula trans-[Ru(L)(PPh₃)₂Cl] in 55-60% yields. The complexes have been characterized with the help of elemental analysis, magnetic susceptibility, electrochemical and various spectroscopic (infrared, electronic and EPR) measurements. The +3 oxidation state of the metal centre in these complexes is confirmed by their one-electron paramagnetic nature. Molecular structures of two representative complexes have been determined by X-ray crystallography. In each complex, the metal ion is in a distorted octahedral CNOClP₂ coordination sphere. The dianionic C,N,O-donor ligand (L²⁻) together with the chloride form a CNOCl square-plane and the P-atoms of the two PPh₃ molecules occupy the two axial sites. The electronic spectra of the complexes in dichloromethane solutions display several absorptions due to ligand-to-metal charge transfer and ligand centred transitions. In dichloromethane solutions, the complexes display a ruthenium(III) → ruthenium(IV) oxidation in the potential range 0.35-0.98 V (vs. Ag/AgCl). All the complexes in frozen (110 K) dichloromethane-toluene (1:1) solutions display rhombic EPR spectra.     

Synthesis,characterization and antibacterial activity of indium(III) complexes with adamantane-ring containing Schiff bases

Indium(III) chloride tetrahydrate and Schiff-base ligands derived from adamantaneamine and 3-/4-methoxysalicylaldehyde gave two complexes, C₂₂H₃₂Cl₃InN₂O₃ (1) and C₃₆H₄₄C_l3InN₂O₄ (2), respectively. The complexes were characterized by IR, ¹H NMR, elemental analysis, molar conductance, thermal analysis, and single-crystal X-ray diffraction. Complex 1 crystallizes in the monoclinic system, P2₁/n space group with the asymmetric unit consisting of one indium(III), one N-(3-methoxysalicylidene)-aminoadamantane (L¹), three chlorides and one N,N-dimethylformamide molecule. The indium is six-coordinate with reversed triangular-prism geometry via three oxygens and three chlorides. Complex 2 crystallizes in the triclinic system, P 1 space group; the asymmetric unit consists of one indium(III), two N-(4methoxysalicylidene)-aminoadamantane (L²), and three chlorides. The indium is five-coordinate with distorted trigonal-bipyramidal geometry via two oxygens and three chlorides. Antibacterial activities of the complexes have been investigated against Escherichia coli and Staphylococcus aureus.     

Complexes of iron(III) salen and saloph Schiff bases with bridging dicarboxylic and tricarboxylic acids

Six new dinuclear or trinuclear FeIII complexes involving tetradentate Schiff bases N,N′-bis(salicylidene)ethylenediamine (salenH2) or bis(salicylidene)-o-phenylenediamine (salophH2) with 2,5-pyridinedicarboxylic acid, acetylenedicarboxylic acid or 1,3,5-benzenetricarboxylic acid have been synthesized and characterized by means of elemental analysis, i.r. spectroscopy, thermal analyses, conductivity measurements and variable-temperature magnetochemical measurements to the temperature of liquid nitrogen. The complexes can be characterized as high-spin distorted octahedral FeIII bridged by carboxylic acids. The dicarboxylic or tricarboxylic acids play a role as bridges for weak antiferromagnetic intramolecular exchange. The antiferromagnetic coupling parameters J vary in the -1.99 to -5.47cm-1 range for the dimers, whilst the values are -2.35 and -1.42cm-1 for the salen and saloph trimers, respectively. One complex, namely [{Fe(saloph)}2(2,5-dicarpy)]middot H2O, obeys the Curie-Weiss law. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis,structural characterization and biological studies of neodymium(III) and samarium(III) complexes with mercaptotriazole Schiff bases

A series of neodymium(III) and samarium(III) complexes of type [Ln(L)Cl(H₂O)₃] have been synthesized with Schiff bases (LH₂) derived from 3‐(phenyl/substituted phenyl)‐4‐amino‐5‐mercapto‐1,2,4‐triazoles and isatin. The structures of the complexes were established using elemental analysis, molar conductivities, magnetic moments, infrared, NMR (¹H, ¹³C) and UV–visible spectra, X‐ray diffraction and mass spectrometry. The thermal behaviour of these compounds under non‐isothermal conditions was investigated using thermogravimetry and differential thermogravimetry. The intermediates obtained at the end of various thermal decomposition steps were identified from elemental analysis and infrared spectral studies. All the ligands and their complexes were also screened for their antibacterial activity against Staphylococcus aureus and Bacillus subtilis and antifungal activity against Aspergillus niger, Aspergillus flavus and Colletotrichum capsici. The screening results were correlated with the structural features of the compounds. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and characterization of some nickel(II) Schiff bases complexes

Summary The reaction of nickel(II) salts with 2-picolyl- and 2,6-lutidyl-phenylketone benzoylhydrazone and theirp-nitro- andp-methoxy-derivatives were carried out and the compounds characterized on the basis of analytical and spectral data.     

Green synthesis,characterization, and DFT calculations of diorganotin (IV) complexes of Schiff bases

Diorganotin (IV) complexes (1, 2, 3, 4), of the general formula R₂Sn(L)_m have been synthesized where R = n-But, n-Oct; m = 2 when L1 = N-[(Z)-(2-hydroxy-3-methoxybenzylidene)pyrazine-2-carboxamide and m = 1 when L2 = [3,4-bis-{[(E)-(2-hydroxy-3-methoxyphenyl) methylidene]amino}phenyl](phenyl)meth-anone. The prepared Schiff bases and diorganotin complexes have been characterized by elemental analysis, FTIR, and NMR (¹H, ¹³C, and ¹¹⁹Sn) spectroscopic studies. The molecular geometry, thermochemical values, and vibrational frequencies of two complexes in the ground state were calculated using the B3LYP density functional method with LANL2DZ basis set for Sn using Gaussian 09 software. A good correlation of theoretical and experimental results shows that in both the complexes the geometry around the central tin atom is tetrahedral. The studies were further extended to test and compare the in vitro cytotoxic activity of ligands and complexes against MCF-7 cell line by MTT assay. The IC50 values show that cytotoxic activity of ligands increased on complexation with tin metal.     

Synthesis and characterization of tetra-armed-thiosemicarbazone and its salen/salophen capped transition metal complexes: Investigation of their thermal and magnetic properties

In this work, we aimed to synthesize and characterize a novel tetra-directional ligand, (2E,2′E)-2,2′-((((2-(1,3-bis(4-((E)-(2-carbamothioylhydrazono)methyl)phenoxy)propan-2-ylidene)propane-1,3-diyl)bis(oxy))bis(4,1-phenylene))bis(methanylylidene))bis(hydrazinecarbothioamide) (5), including thiosemicarbazone group and its novel tetra-directional-tetra-nuclear Schiff base complexes. For this purpose, we used 1,4-dibromo-2,3-bis(bromomethyl)but-2-ene (2) as starting material. 4,4′-((2-(1,3-Bis(4-formylphenoxy)propan-2-ylidene)propane-1,3-diyl) bis(oxy))dibenzaldehyde (3) was synthesized by the reaction of an equivalent 1,4-dibromo-2,3-bis(bromomethyl)but-2-ene (2) and 4 equivalents of 4-hydroxybenzaldehyde. Then, compound 5 was synthesized in high yield (86%) by a condensation reaction of compound 3 with thiosemicarbazide (4). Finally, four novel tetra-nuclear Cr(III) or Fe(III) complexes of compound 5 were synthesized. The synthesized compounds were characterized using elemental analyses, ¹H NMR, Fourier transform–infrared spectrometry, liquid chromatography–mass spectrometry (ESI⁺), and thermal analyses. The metal ratios of the prepared complexes were determined using an atomic absorption spectrophotometer. We also investigated their effects on the magnetic behaviors of [salen, salophen, Cr(III)/Fe(III)] capped complexes. The complexes were found to be low-spin distorted octahedral Fe(III) and distorted octahedral Cr(III), all bridged by thiosemicarbazone.     

Potentiometric and antimicrobial studies on the asymmetric Schiff bases and their binuclear Ni(II) and Fe(III) complexes; synthesis and characterization of the complexes

The protonation constants of two nitro-Schiff bases SB¹, SB² and three asymmetric tetradentate diimines H₂L¹, H₂L² and H₂L³ and the stability constants of their ML type binuclear Ni(II) and Fe(III) complexes have been determined potentiometrically. The asymmetric diimines are (2OH) RCHNC₆H₄CHNR′ (2OH) type compounds [where R = R′ = phenyl for H₂L¹; R = naphthyl, R′ = phenyl for H₂L² and R = R′ = naphthyl for H₂L³]. The effect of tautomeric forms on the acid-base properties of the diimines has been investigated and discussed. In addition, dimeric and binuclear Ni(II) and Fe(III) complexes of the diimines have been synthesized and characterized by physical and spectroscopic techniques. Also, in vitro antimicrobial activities of the diimines and the complexes have been evaluated against three bacteria: Micrococcus luteus (NRLL B-4375), Bacillus cereus (RSKK 863), Escherichia coli (ATCC 11230) and the fungus: Candida albicans (ATCC 10239).     

Synthesis,characterization, optical and anti-bacterial properties of benzothiazole Schiff bases and their lanthanide (III) complexes

Two new Schiff base ligands comprising benzothiazole derivatives, namely (N,N′,E,N,N′E)-N,N′-(1,3-phenylenebis(methanylylidene))bis(5-nitrobenzo[d]thiazoL2-amine (L1) and (N,N′,E,N,N′E)-N,N′-(1,3-phenylene-bis(methanylylidene))bis(5-methylthiazo-L2-amine (L2), have been synthesized and thoroughly characterized using FTIR, ¹H NMR, mass UV/vis and fluorescence spectral techniques. Further, L1 and L2 lead to the formation of lanthanide complexes 1–6 with Ce(III), Nd(III), and Pr(III) ions in 1:2 (metal:ligand) stoichiometry. UV/vis spectra of L1, L2 and 1–6 exhibit characteristic ligand centered absorptions in the range of 230–350 nm. Besides, both ligands and complexes show significant emissions and good anti-bacterial activity against pathogenic bacteria. Ligands and complexes display anti-bacterial activity against bacteria Staphylococcus aureus (S. aureus) (MTCC 1144) causing skin infection and food poisoning and pimple-causing bacteria propionic bacteria acnes (P. acnes) (MTCC 1951).     

Ruthenium(II)/(III) complexes of bidentate acetyl hydrazide Schiff bases

A series of octahedral Ru^II/Ru^III complexes of the type [Ru(Y)(CO)(BAX)(PPh₃)₂] and [RuCl₂(BAX)(PPh₃)₂] (Y = H or Cl; BAX = benzaldehydeacetylhydrazone anion; X = H, Me, OMe, OH, Cl or NO₂) have been prepared and characterised by spectral, magnetic and cyclic voltammetric studies. The Ru^II complexes are low spin diamagnetic (S = 0) whereas the Ru^III complexes are low spin and paramagnetic (S = 1/2). These Ru^II and Ru^III complexes absorb in the visible region respectively at ca. 16,000 and 28,000 cm^–1 which bands are assigned to the MLCT. The correlation of the _max values of the Ru^III complexes with the ⁺ Hammett parameter, is linear, indicating the profound effect of substituents on the electron density of the central metal. I.r. spectral data reveals that the hydrazone is chelated to ruthenium through the hydrazinic nitrogen and the deprotonated enolic oxygen. The rhombic nature of the e.s.r. spectra of the Ru^III complexes indicates an asymmetry in the electronic environment around the Ru atom. Ru^II complexes in CH₂Cl₂ show an irreversible Ru^II/III redox couple at ca. 0.9–0.5 V, while the Ru^III complexes show two reversible redox couples in the –0.1–0.1 and 0.8–0.6 V range, indicating that the higher oxidation state of ruthenium is stabilised by hydrazones.     

Oxorhenium(V) complexes with bidentate carbohydrazide Schiff bases: synthesis,characterization and DNA interaction studies

The respective coordination reactions of trans-[ReOCl₃(PPh₃)₂] with N-[(4-oxo-4H-chromen-3-yl)methylidene]thiophene-2-carbohydrazide (Hchrtc) and N-[1,3-benzothiazol-2-ylmethylidene]thiophene-2-carbohydrazide (Hbztc) afforded two novel oxorhenium(V) complexes, cis-[ReOCl₂(chrtc)(PPh₃)] (1) and cis-[ReOCl₂(bztc)(PPh₃)] (2). These metal compounds were elucidated spectroscopically and their solid-state structures determined by single-crystal X-ray diffraction. The redox properties of the metal complexes were probed using cyclic and square wave voltammetry. The DNA interaction capabilities of 1 and 2 were gauged via UV/Vis spectroscopy DNA titrations and gel electrophoresis studies. A correlation is identified between the DNA cleavage observations and the redox potentials of the metal complexes.     

The (salophen)-bridged Fe/Cr (III) capped complexes with triphenylene core: Synthesis and characterization

This article describes synthesis of the difference carboxylic acid derivatives of triphenylene and its complexation properties with Fe/Cr (III)-salophen. For this purpose, the carboxylic acid derivatives of 2,3,6,7,10,11-hexahydroxytriphenylene were synthesized and then reacted with four new Fe(III) and Cr(III) complexes involving tetradenta Schiff bases bis(salicylidene)-o-phenylenediamine-(salophenH₂). The prepared compounds were characterized by means of elemental analysis carrying out infrared spectroscopy (IR), thermogravimetric analysis (TG), nuclear magnetic resonance (¹H NMR), elemental analysis and magnetic susceptibility measurement. The complexes can also be characterized as low-spin distorted octahedral Fe(III) and Cr (III) bridged by carboxylic acids.     

Co(III) and Fe(III) complexes of Schiff bases derived from 2,4-dihydroxybenzaldehyde S-allyl-isothiosemicarbazonehydrobromide

Two new complexes, [Co(L¹)(Py)₃]Cl_0.75Br_0.25 (L¹=4-hydroxy salicylaldehyde S-allyl-isothiosemicarbazonato-N,N′,O) and [Fe(L²)Cl]·C₂H₅OH (L²=S-allyl-N¹-(4-hydroxy salicylaldehyde)-N⁴-(salicylaldehyde)isothiosemicarbazide-N,N′,O,O′), have been synthesized and characterized by elemental analysis, FT-IR and UV–vis spectroscopy, and molar conductivity. The solid-state structures of the complexes were also determined by single crystal X-ray diffraction. The iron(III) and cobalt(III) complexes adopt distorted square-pyramidal and octahedral geometries, respectively. The strength of the bonding in these complexes was investigated by thermogravimetric studies with both exhibiting stability with complete decomposition not occurring until ca. 600?°C.     

New ruthenium(III) complexes containing tetradentate Schiff bases and their antibacterial activity

Ruthenium(III) complexes, [RuX(EPh₃)(LL)] (X = Cl, Br; E = P, As; LL-acactet, dbm-tet, dbm-o-ph), have been synthesised by reacting [RuCl₃(PPh₃)₃], [RuCl₃(AsPh₃)₃], [RuBr₃(AsPh₃)₃] or [RuBr₃(PPh₃)₂(MeOH)] with tetradentate Schiff bases such as bis(acetylacetone)tetramethylenediimine (H₂acactet), bis(dibenzoylmethane)tetramethylenediimine (H₂dbmtet) and bis(dibenzoylmethane)-o-phenylenediimine (H₂dbm-o-ph). All the complexes have been characterised by elemental analysis, i.r., electronic spectra, e.p.r., magnetic moment and cyclic voltammetric data and an octahedral structure has been tentatively proposed. These new complexes have been tested for their antibacterial activities.     

Tetradentate asymmetric Schiff bases and their Ni(II) and Fe(III) complexes

Three asymmetric Schiff-base tetradentate diimines H₂L¹, H₂L², and H₂L³ [(2-OH)C₆H₄N=CHC₆H₄2-N=CHC₆H₃(2-OH)(5-X), X?=?H, CH₃, Cl respectively] have been synthesized by a two step process. The reaction of 2-hydroxy aniline with 2-nitro-benzaldehyde in EtOH gave the starting Schiff base, 2-hydroxy-N-(2-nitrobenzylidene)aniline (SB-NO₂), which was reduced into the amino derivative (SB-NH₂) in solution. Reacting SB-NH₂ with 2-hydroxybenzaldehyde, 2-hydroxy-5-methylbenzaldehyde and 2-hydroxy-5-chlorobenzaldehyde gave the three new ligands H₂L¹, H₂L², and H₂L³ respectively. Their dimeric, binuclear metal complexes with Ni(II) and Fe(III) have also been synthesized. The ligands and their complexes were characterized by elemental analyses, LC–MS, IR, electronic, ¹H and ¹³C-NMR spectra, TGA, conductivity and magnetic measurements. All of the spectroscopic, analytical and other data indicate octahedral geometry M₂L₂(H₂O)X₂ (M: Ni,Co;X: Cl or H₂O), except for NiL² which is monomeric. Antimicrobial activities of the ligands and the complexes were evaluated against five bacteria. While the ligands and the Ni complexes are inactive towards Pseudomonas aeruginosa and Staphylococcus aureus, Fe complexes are active; only Fe complexes are inactive against Escherichia coli. All of the compounds have antimicrobial activities against Bacillus subtilis, and Yersinia enterecolitica.     

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.