Synthesis and spectral studies of new N2S2 and N2O2 Mannich base ligands and their metal complexes

New Mannich bases bis(thiosemicarbazide methyl) phosphinic acid H₃L¹ and bis(1-phenylsemicarbazide methyl) phosphinic acid H₃L² were synthesized from condensation of phosphinic acid and formaldehyde with thiosemicarbazide and 1-phenylsemicarbazide, respectively. Monomeric complexes of these ligands, of general formula K₂[Cr^III(L ⁿ )Cl₂], K₃[Fe^II(L¹)Cl₂], K₃[Mn^II(L²)Cl₂], and K[M(L ⁿ )] (M = Co(II), Ni(II), Cu(II), Zn(II) or Cd(II); n = 1, 2) are reported. The mode of bonding and overall geometry of the complexes were determined through IR, UV-Vis, NMR, and mass spectral studies, magnetic moment measurements, elemental analysis, metal content, and conductance. These studies revealed octahedral geometries for the Cr(III), Mn(II), and Fe(II) complexes, square planar for Co(II), Ni(II), and Cu(II) complexes and tetrahedral for the Zn(II) and Cd(II) complexes. Complex formation via molar ratio in DMF solution has been investigated and results were consistent to those found in the solid complexes with a ratio of (M : L) as (1 : 1).     

Synthesis and physico-chemical studies on transition metal complexes of symmetric bis-Schiff base ligands

Transition Metal Chemistry - A new series of symmetric bis-Schiff bases derived from 1,2-diaminoethane with bis-salicylaldehyde (H2L1) and/or bis-o-hydroxyacetophenone (H2L2) have been prepared....     

Synthesis, structural characterization and electrochemical studies of new macrocyclic Schiff base containing pyridine head and its metal complexes

A new macrocyclic ligand, 1,3,5-triaza-2,4:7,8:13,14-tribenzo-9,12-dioksa-cyclopentadeca-1,5-diene was synthesized by reaction of 2,6-diaminopyridine and 1,2-bis(2-carboxyaldehyde phenoxy)ethane. Then, its Cu(II), Ni(II), Pb(II), Co(III) and La(III) complexes were synthesized by the template effect by the reaction of 2,6-diaminopyridine and 1,2-bis(2-carboxyaldehyde phenoxy)ethane and Cu(NO₃)₂ · 3H₂O, Ni(NO₃)₂ · 6H₂O, Pb(NO₃)₂, Co(NO₃)₂ · 6H₂O, La(NO₃)₃ · 6H₂O, respectively. The ligand and its metal complexes have been characterized by elemental analysis, IR, ¹H and ¹³C NMR, UV-Vis spectra, magnetic susceptibility, thermal gravimetric analysis, conductivity measurements, mass spectra, and cyclic voltammetry. All complexes are diamagnetic and Cu(II) complex is binuclear. The Co(II) was oxidized to Co(III). The comparative electrochemical studies show that the nickel complex exhibited a quasi-reversible one-electron reduction process, while copper and cobalt complexes gave irreversible reduction processes in DMSO solution.     

Synthesis and structural characterization of new multiferrocenyl diyne ligands and their cobalt carbonyl complexes

New multiferrocenyl diyne ligands FcC(CH₃)₂Fc′–C≡C–C≡C–Fc [L ₁ ; Fc?=?C₅H₅FeC₅H₄; Fc′?=?C₅H₅Fe(1,3-disubstituted)C₅H₃], FcC(CH₃)₂Fc′–C≡C–C≡C–Fc′C(CH₃)₂Fc (L ₂ ) and their complexes [FcC(CH₃)₂Fc′–C≡C–C≡C–Fc][Co₂(CO)₆] _n [n?=?1, (1); n?=?2, (2)], [FcC(CH₃)₂Fc′–C≡C–C≡C–Fc′C(CH₃)₂Fc][Co₂(CO)₆] _n [n?=?1, (3); n?=?2, (4)] have been synthesized by the coupling reaction of terminal ferrocenylacetylene and the reaction of ligands L₁ and L₂ with Co₂(CO)₈. The composition and molecular structure of the ligands L₁ , L₂ and their cobalt complexes were characterized by element analysis, IR, ¹H(¹³C)NMR and MS. The electrochemical properties of compounds L₁ , L₂ , 1, 2, 3, 4 were studied by cyclic voltammetry(CV). The results of the electrochemical research reveal that all three ferrocenyl groups in L₁ become redox active centers, but there are only two (not four) ferrocenyl redox active centers in L₂ .     

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.     

Synthesis and characterization of oxodiperoxo complexes of tungsten(VI) with some Mannich base ligands

Six oxodiperoxotungsten(VI) complexes, [WO(O₂)₂L–L] (where L–L?=?morpholinobenzyl benzamide (MBB), piperidinobenzyl benzamide (PBB), piperidinobenzyl urea (PBU), morpholinobenzyl urea (MBU), piperidinobenzyl thiourea (PBTU) and morpholinobenzyl thiourea (MBTU)) have been prepared by stirring WO₃?·?H₂O with excess 30% aqueous (w/v) H₂O₂ and then treating with an ethanolic solution of the Mannich base ligand (L–L). These have been characterized by elemental analysis, conductance and magnetic susceptibility measurements, IR spectra, electronic spectra, ¹H NMR, TGA/DTA and cyclic voltammetric studies. These complexes are non-electrolytes and diamagnetic in nature. The ligands are bound to metal in a bidentate mode through carbonyl oxygen/thiocarbonyl sulphur and the ring nitrogen. The complexes also inhibit the growth of pathogen “Fusarium Spp.” up to 60%. The cyclic voltammograms of the complexes indicate quasi-reversible redox steps involving complexes.     

Synthesis and characterization of peroxo complexes of uranium(VI) with some Mannich base ligands

Abstract  

Uranium(VI) peroxo complexes of composition [UO(O₂)L–L(NO₃)₂], where L–L are the Mannich base ligands morpholinobenzyl urea, piperidinobenzyl urea, morpholinobenzyl thiourea, piperidinobenzyl thiourea, morpholinomethyl thiourea, piperidinomethyl thiourea, or morpholinomethyl urea, are reported. The synthesized complexes were characterized by use of a variety of physicochemical techniques, viz. elemental analysis, molar conductivity, magnetic susceptibility measurements, IR, electronic, mass, ¹H NMR, and ¹³C NMR spectroscopy, and TGA/DTA studies. These studies revealed that the complexes are both non-electrolytic and diamagnetic in nature. The ligands are bound to the metal in a bidentate mode through carbonyl oxygen or thiocarbonyl sulfur and the ring nitrogen. Mass spectra confirm the molecular mass of the complexes. The antifungal activity of the complexes is greater than that of the corresponding free ligands.     

Synthesis, characterization and biological activity of bis(phenylimine) Schiff base ligands and their metal complexes

Metal complexes derived from 2,6-pyridinedicarboxaldehydebis(p-hydroxyphenylimine); L1, 2,6-pyridinedicarboxaldehydebis (o-hydroxyphenylimine); L2, are reported and characterized based on elemental analyses, IR, solid reflectance, magnetic moment, molar conductance and thermal analysis (TGA). The complexes are found to have the formulae [MX2(L1 or L2)] x nH2O, where M=Fe(II), Co(II), Ni(II), Cu(II) and Zn(II), X=Cl in case of Fe(II), Co(II), Ni(II), Cu(II) complexes and Br in case of Zn(II) complexes and n=0-2.5. The molar conductance data reveal that the chelates are non-electrolytes. IR spectra show that the Schiff bases are coordinated to the metal ions in a terdentate manner with NNN donor sites of the pyridine-N and two azomethine-N. From the magnetic and solid reflectance spectra, it is found that the geometrical structure of these complexes are trigonal bipyramidal (in case of Co(II), Ni(II), Cu(II) and Zn(II) complexes) and octahedral (in case of Fe(II) complexes). 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 coordinated water, anions and ligands (L1 and L2) in the subsequent steps. The activation thermodynamic parameters, such as, E*, DeltaH*, DeltaS* and DeltaG* are calculated from the TG curves using Coats-Redfern method. The synthesized ligands, in comparison to their metal complexes also were screened for their antibacterial activity against bacterial species, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Fungi (Candida). The activity data show that the metal complexes to be more potent/antibacterial than the parent organic ligands against one or more bacterial species.     

Synthesis and structural studies on bivalent metal complexes of benzenesulphonylhydrazine

Summary Benzenesulphonylhydrazine (HB) reacts with bivalent metal ions either in the keto-or enol forms. The complexes have been characterized by spectral (u.v., i.r., n.m.r.,), magnetic and thermal (d.t.a., d.t.g, t.g., d.s.c.) measurements. I.r. spectra suggest that HB is monodentate coordinatingvia NH or NH₂, depending on the medium of the reaction. The participation of the O=S=O group in bondingvia bridge-formation in a polymeric chain is also considered. The substitution of ethanol in the Co^II complex, [(CoB₂EtOH)_n], by H₂O, pyridine or acetonitrile was also investigated.     

Transition metal complexes of bidentate Schiff base ligands

New Schiff base ligands derived from vanillin (HL¹), 4-dimethylaminobenzaldehyde (HL²) and 3,5-di-t-butyl-4-hydroxybenzaldehyde (HL³) with N-(pyridyl)-3-methoxy-4-hydroxy-5-aminobenzylamine (2) and their copper(II), cobalt(II), nickel(II), oxovanadium(IV) and zinc(II) transition metal complexes have been synthesized and characterized by elemental analyses, electronic and i.r. spectra, molar conductance data and by 1H and ¹³C n.m.r. spectra. The results indicate that the ligands coordinate through azomethine nitrogen and phenolic oxygen to the metal ions. In like manner, it was found that the pyridine and amine nitrogen atoms are not coordinated to the metal ions. The ¹H and ¹³C n.m.r. spectral data confirmed the suggested structure for the Schiff base ligands, and the mass spectra results confirmed the proposed structure of the ligands. The antimicrobial activity properties of the ligands and their metal complexes have been studied.     

Synthesis of new lariat cyclicdiamides and their metal complexes

Three new lariat dilactam host molecules were prepared by the reaction of triethyleneglycol dicarboxylic acid dichloride withN,N-disubstitutèd-4,7-dioxa-1,10-diazadecane precursors. The amide nitrogen pivot of such compounds are substituted with the benzyl, octyl and dodecyl groups. The complexing ability of these dilactams is displayed with a series of metal complexes of Na⁺, K⁺, Ca²⁺, Sr²⁺, Pb²⁺ and Ag⁺ ions. The structures determined are consistent with the data of¹H-NMR,¹³C-NMR, IR spectra and elemental analyses.Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August, 1995.     

Dinuclear peroxo complexes of molybdenum(VI) containing Mannich base ligands

Dinuclear molybdenum(VI) peroxo complexes containing Mannich base ligands having formulae [Mo₂O₄(O₂)₂L-L(H₂O)₂] · H₂O [where L-L = N-[1-morpholinobenzyl] acetamide (MBA), N-[1-piperidinobenzyl] acetamide (PBA), N-[1-morpholino(-4-nitrobenzyl)] benzamide (MPNBB), N-[1-piperidino(-3-nitrobenzyl)] benzamide (PMNBB), N-[1-morpholino(-2-nitrobenzyl)] acetamide (MONBA), and N-[1-morpholino(-3-nitrobenzyl)] acetamide (MMNBA)] have been synthesized by stirring ammonium heptamolybdate with excess 30% aqueous hydrogen peroxide followed by treatment with ethanolic solution of corresponding ligands. The complexes have been characterized by elemental analysis, molar conductance, magnetic measurements, infrared (IR), electronic, TGA/DTA, mass spectral, and ¹H NMR studies. The complexes are non-electrolytes and diamagnetic. The IR spectral studies suggest that the ligands are bidentate to metal through carbonyl oxygen and ring nitrogen. Thermal analyses provide conclusive evidence for the presence of coordinated, as well as lattice water in the complexes. Dinuclear complexes preserve the individuality of the molybdenum oxo peroxo core. The complexes exhibit higher antibacterial activity against bacterium Ralastonia solanacearum (Pseudomonas solanacearum) than the free ligands.     

Synthesis and physicochemical studies of metal complexes of ferrocene Schiff base derivatives

Two new Schiff bases were prepared by condensing acetylferrocene and 1,1′-diacetylferrocene with S-methyl- dithiocarbazate. Complexes of the two ligands acetylferrocene-1-hydrazono-S-methyldithiocarbazate HmaL and diacetylferrocene-1,1′-dihydrazono-S-methyldithio-carbazate H2daL, with copper(II), nickel(II) and cobalt(II) ions were isolated. The ligands coordinate to the metal ions through either their thioketone or thioenol forms. Both mono- and bis-ligand metal complexes as well as bis-metal complexes of the general formulae: [(H2daL)M]2+, [(daL)M], [(HmaL)2M]2+, [(maL)2M], [(HmaL)2MX2], [(H2daL)M2X4] and [(daL)M2X2] were prepared. All compounds under investigation were characterized and some of their physicochemical properties are reported. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis,characterization of Schiff base metal complexes and their biological investigation

A new Schiff base ligand named (E)‐2‐(((3‐aminophenyl)imino)methyl)phenol (HL) was prepared through condensation reaction of m‐phenylenediamine and 2‐hydroxybenzaldehyde in 1:1 molar ratio. The new ligand was characterized by elemental analysis and spectral techniques. The coordination behavior of a series of transition metal ions named Cr (III), Mn (II), Fe (III), Co (II), Ni (II), Cu (II), Zn (II) and Cd (II) with the newly prepared Schiff base ligand (HL) is reported. The nature of bonding and the stereochemistry of the complexes have been deduced from elemental analyses, IR, UV–Vis, ¹H NMR, mass, electronic spectra, magnetic susceptibility and conductivity measurements and further their thermal stability was confirmed by thermogravimetric analysis (TG). From IR spectra, it was observed that the ligand is a neutral tridentate ligand coordinates to the metal ions through protonated phenolic oxygen, azomethine nitrogen and nitrogen atom of NH₂ group. The existence, the number and the position of the water molecules was studied by thermal analysis. The molecular structures of the Schiff base ligand (HL) and its metal complexes were optimized theoretically and the quantum chemical parameters were calculated. The synthesized ligand and its complexes were screened for antimicrobial activities against bacterial species (Staphylococcus aureus and Bacillis subtilis, (gram positive bacteria)), (Salmonella SP., Escherichia coli and Pseudomonas aeruginosa, (gram negative bacteria)) and fungi (Aspergillus fumigatus and Candida albicans). The complexes were found to possess high biological activities against different organisms. Molecular docking was used to predict the efficiency of binding between Schiff base ligand (HL) and both receptors of Escherichia coli (3 T88) and Staphylococcus aureus (3Q8U). The receptor of Escherichia coli (3 T88) showed best interaction with Schiff base ligand (HL) compared to receptor of Staphylococcus aureu (3Q8U).     

Synthesis of new ligands for transition metal complexes: menthyl- and neomenthyl-cyclopentadienes

Syntheses of (?)-menthylcyclopentadiene (MCp) and (+)-neomenthyl cyclopentadiene (NMCp) from (?)-menthol are described. These chiral ligands have been used to prepare (η⁵-MCp)₂TiCl₂, (η⁵-NMCp)₂, TiCl₂, (η⁵-MCp)₂ZrCl₂, (η⁵-NMCp)₂ZrCl₂, (η⁵-Cp)(η⁵-MCp)TiCl₂ and (η⁵-Cp)(η⁵-NMCp)TiCl₂. The structure and absolute configuration of (η⁵-Cp)(η⁵-MCp)TiCl₂ has been established by X-ray analysis.     

Exogenous bridging and nonbridging in Cu(II) complexes of Mannich base ligands: Synthesis and physical properties

Preparation of pentadentate ligands L¹, L², L³ and L⁴, where L¹ = 4-chloro-3-methyl-2[(prolin-1-yl)methyl]-6-[N-phenyl piperazin-1-yl)methyl]phenol, L² = 4-ethyl-2-[(prolin-1-yl)methyl]-6-[(N-phenyl piperazin-1-yl)methyl]phenol, L³ = 4-chloro-3-methyl-2-[(prolin-1-yl)methyl]-6-[N-methyl piperazin-1-yl]methyl phenol, L⁴ = 4-methoxy-2-[(prolin-1-yl)methyl]-6-[(N-phenyl piperazin-1-yl)methyl]phenol is described together with that of the corresponding Cu(II) complexes with various bridging motifs like OH, OAc and NO₂. The complexes are characterized by elemental analysis, electrochemical and electron paramagnetic spectral studies. Redox properties of the complexes in acetonitrile are highly quasireversible due to the chemical or/and stereochemical changes subsequent to electron transfer. The complexes show resolved copper hyperfine EPR at room temperature, indicating the presence of weak antiferromagnetic coupling between the copper atoms. Strengths of the antiferromagnetic interactions are in the order NO₂>OAc>OH.     

Antimicrobial activity studies of the binuclear metal complexes derived from tridentate Schiff base ligands

Three novel tridentate Schiff base ligands derived fromthe 3-hydroxysalicylaldehyde (H₂L¹), 4-hydroxysalicylaldehyde (H₂L²) and 5-bromosalicylaldehyde (H₂L³) with a new amine N-(pyridyl)-2-hydroxy-3-methoxy-5-aminobenzylamine (2) have been prepared. The ligands and their metal complexes have been characterized by elemental analyses, conductivity and magnetic susceptibility measurements, i.r., electronic absorption and ¹H and ¹³C n.m.r. spectroscopy. All complexes are binuclear and, in some, the H₂O molecules are coordinated to the metal ion. Antimicrobial activities of the ligands and their complexes have been tested against to the Bacillus subtilis IMG 22 (bacteria), Micrococcus luteus LA 2971 (bacteria) Saccharamyces cerevisiae WET 136 (yeast), and Candida albicans CCM 314 (yeast). Thermal properties of all complexes have been studied by t.g. and d.t.a techniques.     

Mass spectrometric studies on small open-chain piperazine-containing ligands and their transition metal complexes

Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry was used to characterize the complexes formed between open-chain piperazine-containing ligands and transition metal salts (Cobalt, Copper, Zinc, and Cadmium as chlorides, nitrates, and acetates). Only single-charged complexes were observed, formed of one ligand (L) and mainly one metal ion (M). Since the net charge of the complexes was one, a counterion (X) was attached to some of the complexes, with formation of [L + M + X]+ complexes, and a proton was lost from others, as in [L - H + M]+ complexes. In most cases the composition of the complexes was more dependent on the ligand than the metal salt. Collision-induced dissociation measurements showed that complexes with related composition often differed in structure, or that interactions between the ligand and the metal ion were not alike. The metal ion influenced considerably the fragmentation pathways of the ligands, so that the fragmentation products could be used to deduce the binding sites of the metal. The variations observed in fragmentation behavior of complexes possessing the same ligand but different metal ions can mostly be explained by the ionic radius and electronic configuration of the metal ion. The results indicated a preference of the piperazine ring of the coordinated ligand for the boat conformation.     

New quadridentate ONNS ligands and their metal complexes

Summary Two new quadridentate sulphur-nitrogen chelating agents have been prepared and characterized. These ligands yield stable complexes of general formulae, M(ONNS)·xH₂O (M=Ni, Cu, Zn, Cd, Pd and Pt; ONNS^–2=ligand dianion; x=0, 1 or 2) and M(ONNS)X (M=Co or Fe; X=Cl or AcO). The nicke(II) complexes are diamagnetic and squareplanar. Based on magnetic and spectral data a square-planar structure is also assigned to the copper(II) complexes. The iron(III) complexes, Fe(ONNS)Cl are high-spin and five-coordinate. Magnetic and spectral evidence support an octahedral structure for the cobalt(III) complex, Co(ONNS)OAc.