Synthesis and characterization of copper(II), cobalt(II), nickel(II), and iron(III) complexes with two diamine Schiff bases and catalytic reactivity of a chiral diamine cobalt(II) complex

New transition metal complexes of Co(II), Cu(II), Ni(II), and Fe(III) of the ligands 6,6′-(1E,1′E)-(4,5-dimethyl-1,2-phenylene)bis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)bis(7-hydroxy-5-methoxy-2-methyl-4H-chromen-4-one) H₂L¹ and 6,6’-(1E,1′E)-cyclohexane-1,2-diylbis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)bis(7-hydroxy-5-methoxy-2-methyl-4H-chromen-4-one) H₂L² have been prepared and characterized using physio-chemical and spectroscopic methods. The results obtained for the complexes indicated that the geometries of the metal centres are either square planar or octahedral. Cyclopropanation reactions of unactivated olefins by ethyldiazoacetate (EDA) in the presence of [L¹Cu]·H₂O, [L²Cu]·2H₂O and [L²*Co]·2H₂O as catalysts were examined. The results showed that only [L²*Co]·2H₂O can act as a catalyst for the cyclopropanation reaction of unactivated olefins with very high selectivity (up to 99% based on EDA).     

Developments in transfer hydrogenations of aromatic ketones catalyzed by boron compounds

Boron complexes BL1 and BL2 were prepared from O-donor ligands, 2,2′-(1E,1′E)-(ethane-1,2-diylbis(azan-1-yl-1-ylidene))bis(methane-1-yl-1-ylidene)diphenol (L1) and 2,2′-(propane-1,3-diylbis(azan-1-yl-1-ylidene))bis(methane-1-yl-1-ylidene)diphenol (L2). The complexes were fully characterized by ¹H and ¹³C NMR, LC-MS/MS, TGA/DTA, UV-Vis, elemental analysis, SEM, and FTIR. The transfer hydrogenation of acetophenone derivatives was investigated by the boron complexes in the presence of isoPrOH, as the hydrogen source, under basic condition with NaOH. The results showed that the boron complexes were promising catalytic precursors for transfer hydrogenation of aromatic ketones in 0.1 M isoPrOH solution (up to 99%). Both steric and electronic factors of this class of molecules had a significant impact on the catalytic properties.     

Studies on the Synthesis and Thermodynamic Stability of Two Multidentate Ligands 2,9-disubstituted 1,10-phenanthroline

Two multidentate ligands: N,N′-di-(propionic acid-2′-yl-)-2,9-di-aminomethylphenanthroline (L₁) and N,N′-di-(3′-methylbutyric acid-2′-yl-)-2,9-di-amino-methylphenanthroline (L₂) were synthesized and fully characterized by ¹H NMR and elemental analysis. The binding ability of L₁ and L₂ to metal ions such as M(II) (M = Cu, Zn, Co and Ni) and Ln(III) (Ln = La, Nd, Sm, Eu, and Gd) has been investigated by potentiometric titration in aqueous solution and 0.1 mol dm⁻³KNO₃ at 25.0 ± °C. In view of the structure of L₁ and L₂, mononuclear metal complexes can be formed in solution. The stability constants of binary complexes of ligands L1 and L2 with metal ions M(II) and Ln(III) have been determined respectively and further discussed.     

The synthesis and characterization of ( E,E )-dioxime and its transition metal complexes containing 12-membered macrocycles linked to ferrocenyl-methyl groups

13,14-bis(Hydroxyimino)-4,7-bis(ferrocenylmethyl)-2,3,4,5,6,7,8,9-octahydrobenzo[k]-4, 7-diaza-1,10-dithiacyclododecine[13,14-g]-quinoxaline (H₂L) has been prepared from (E,E)-dichloroglyoxime and 12,13-diamino-4,7-bis(ferrocenylmethyl)-2,3,4,5,6,7,8,9-octahydrobenzo[k]-4,7-diaza-1,10-dithiacyclododecine which was synthesized from 12,13-dinitro-4,7-bis(ferrocenylmethyl)-2,3,4,5,6,7,8,9-octahydrobenzo[k]4,7-diaza-1,10-dithia cyclododecine. Mononuclear nickel(II) and copper(II) complexes of H₂L have a metal-ligand ratio of 1?:?2 and the ligand coordinates through two nitrogen atoms, as do most (E,E)-dioximes. The homotrinuclear [Cu(L)₂Cu₂(dipy)₂](NO₃)₂ compound coordinates to the other two copper(II) ions through deprotonated oximate oxygens and two 2,2′-dipyridyl as an end-cap ligand to yield the trinuclear structure. The ligand and its complexes have been characterized on the basis of ¹H, ¹³C NMR, IR and MS spectroscopy and elemental analyses.     

Synthesis and characterization of novel (<Emphasis Type="Italic">E</Emphasis>,<Emphasis Type="Italic">E</Emphasis>)-dioxime and its mono- and polynuclear metal complexes containing azacrown moieties

The novel (E,E)-dioxime,7,8-bis(hydroxyimino)-1,14-bis(monoaza[8]crown-6)-benzo[f]-4,11-dioxa-1,14-diazadecane[7,8-g]quinoxaline (H₂L), has been synthesized by the reaction of 6,7-diamino-1,12-bis(monoaza[18]crown-6)benzo[f]-4,9-dioxa-1,12-diazadecane (4) which has been prepared by the reduction of 6,7-dinitro-1,12-bis(mono-aza[18]crown-6)benzo[f]-4,9-dioxa-1,12-diazdecane (3) and cyanogendi-N-oxide. Mononuclear Ni^II and Cu^II complexes of H₂L have a metal:ligand ratio of 1:2 and the ligand coordinates through two hydroxyimino nitrogen atoms, as do most of the (E,E)-dioximes. The hydrogen-bridged Ni^II complex was converted into its BF ₂ ⁺ capped anologue by the reaction with BF₃ · Et₂O. The reaction of the Cu^II complex with 2,2′-dipyridyl as an end-cap ligand gave the homotrinuclear complex. Structures for the ligand and its complexes are proposed in accordance with elemental analysis, magnetic susceptibility measurements, ¹H, ¹³C-n.m.r, IR and MS spectral data.     

Solvent directed templated synthesis of mono- and di(Schiff base) complexes of Ni(II)

The mono- and binuclear complexes Ni(Salen) (I) and Ni₂(Salen)₂ (II) (H₂Salen = N,N′-bis(salicylidene)ethane-1,2-diamine), have been synthesized and structurally characterized by single-crystal X-ray diffraction studies. The X-ray structural analyses show that the metal center of complex I is mononuclear and tetracoordinate with a distorted tetrahedron, whereas the metal-centered complex II is binuclear and pentacoordinate with rectangular pyramid geometries, respectively. The electrochemical studies evidenced for the mononuclear Ni(II) complex shows one quasireversible reduction potential at −0.80 V (E _pc ) and the binuclear Ni(II) complex shows a reduction potential at −0.90 V (E _pc ) in the cathodic region. The article is published in the original.     

Synthesis and structural studies of new Mannich base ligands and their metal complexes

The new Mannich bases bis(1,4-diphenylthiosemicarbazide methyl) phosphinic acid H₃L¹ and bis(1,4-diphenylsemicarbazide methyl) phosphinic acid H₃L² were synthesised from the condensation of phosphinic acid, formaldehyde with 1,4-diphenyl thiosemicarbazide and 1,4-diphenylsemicarbazide, respectively. Monomeric complexes of these ligands, of general formulae K₂[Cr^III(L ⁿ )Cl₂], K₃[Mn^II(L ⁿ )Cl₂] and K[M(L ⁿ )] (M = Co(II), Ni(II), Cu(II), Zn(II) or Hg(II); n = 1, 2), are reported. The mode of bonding and overall geometry of the complexes were determined through physico-chemical and spectroscopic methods. These studies revealed octahedral geometries for the Cr(III), Mn(II) complexes, square planar for Co(II), Ni(II) and Cu(II) complexes and tetrahedral for the Zn(II) and Hg(II) complexes.     

Nano level detection of Cd(II) using poly(vinyl chloride) based membranes of Schiff bases

The construction and performance characteristics of polymeric membrane electrodes based on two neutral ionophores, 2,2′-(1Z,1′Z)-(1E,1′E)-(1,2-phenylenebis(methan-1-yl-1-ylidene))bis(azaan-1-yl-1-ylidene)bis(methylene)bis(azan-1-yl-1-ylidene)bis(methan-1-yl-ylidene)diphenol (L₁) and 4,4′-(1E,1′E)-(butane-1,4-diylbis(azan-1-yl-1-ylidene))bis(methan-1-yl-1-ylidene)dinaphthalen-1-ol (L₂) for quantification of cadmium ions, are described. The influences of membrane compositions on the potentiometric response of the electrodes have been found to substantially improve the performance characteristics. The best performance was obtained with the electrode having a membrane composition (w/w) of (L₁) (2.6%):PVC (31.6%):DOP (63.2%):NaTPB (2.6%). The proposed electrode exhibits Nernstian response in the concentration range 5.0 × 10⁻⁹ to 1.0 × 10⁻¹ M Cd²⁺ with limit of detection 3.1 × 10⁻⁹, performs satisfactorily over wide pH range (2.0-8.5) with a fast response time (11 s). The electrode has been found to work satisfactorily in partially non-aqueous media up to 40% (v/v) content of methanol, ethanol and acetonitrile and could be used for a period of 2.5 months. The analytical usefulness of the proposed electrode has been evaluated by its application in the determination of cadmium in cigarette samples. The practical utility of the membrane electrode has also been observed in the presence of surfactants.     

A new (E,E)-dioxime and its mono and heterotrinuclear complexes containing an 18-membered dithiatetraazamacrocycle

The novel (E,E)-dioxime, 5,6:ll,12:17,18-tribenzo-2,3-bis(hydroxyimino)-7,16-dithia-9, 14-dioxo-l,4,10,13-tetraazacyclooctadecane (H₂L) has been synthesized by reacting (E,E)-dichloroglyoxime (2) with 2,3:8,9:14,15-tribenzo-4,13-di-thia-6,11-dioxa-l,7,10,16-tetraazahexzadecane (3), prepared by the reaction of N,N-bis(chloroacetyl)-1, 2-phenylene-diamine (1) with 2-aminothiophenol. Mononuclear complexes (4, 5) of this ligand have been synthesized by reacting the vic-dioxime (H₂L) with K₂PtCl₄ and NiCl₂ · 6H₂O, respectively. Heterotrinuclear complexes (6)and(7) have been prepared by the reaction of (4) and (5) mononuclear complexes with [Cu(MeCN)₄]PF₆. The structures of the vic-dioxime and its mono and trinuclear complexes were identified by elemental analysis, ¹H- and ¹³C-n.m.r, i.r. and m.s. data.     

Structural elucidation of manganese(II), iron(III), cobalt(II), nickel(II), copper(II) and zinc(II) complexes of a new multidentate dihydrazino quinoxaline derivative

Summary Manganese(II), iron(III), cobalt(II), nickel(II), copper(II) and zinc(II) complexes of a new multidentate oxygen-nitrogen donor, bis(N-salicylidene)-2,3-dihydrazino-1,4-quinoxaline (H₂BSDHQ) were prepared and characterised by elemental analysis, conductance, thermal, spectral and magnetic data. H₂BSDHQ deprotonates to give a dibasic ONNO donor set in a trivalent iron(III) complex, which binds to the divalent metal ions in a bis-tridentate fashion, using two monobasic ONN donor sets, and resulting in polymeric complexes. Octahedral geometries are proposed for all these complexes, and preliminary studies show that they possess potential antimicrobial activity.     

Mononuclear Rare Earth Metal Complexes based on 1,10-phenanthroline Derivatives as Catalysts for Hydrolysis of p-nitrophenyl Phosphate (NPP)

Two multidentate ligands: N,N′-di-(propionic acid-2′-yl-)-2,9-diaminomethyl-1,10-phenanthroline (L1) and N,N′-di-(3′-methylbutyric acid-2′-yl-)-2,9-diaminomethyl-1,10-phenanthroline (L2) were synthesized. The hydrolytic kinetics of p-nitrophenyl phosphate (NPP) catalyzed by complexes of L1 and L2 with La(III), Gd(III) have been studied. Both LnL and LnLH₋₁ have been examined as catalysis for the hydrolysis of NPP in aqueous solution at 298 K, I = 0.10 mol dm⁻³ KNO₃ at the pH range 7.4–9.1, respectively. Kinetic studies show that both LnL and LnLH₋₁ have catalytic activity, but LnLH₋₁ is more active than LnL in the hydrolysis of NPP. The second-order rate constants for the hydrolysis of NPP are k_GdL1H−1 = 0.01399 mol⁻¹ dm³ s⁻¹, k_GdL1 = 0.0000110 mol⁻¹ dm³ s⁻¹ for complexes GdL1H₋₁ and GdL1, respectively. A new mechanism was proposed for the hydrolysis of NPP catalyzed by LnL and LnLH₋₁.     

Antibacterial activity of ruthenium(II) carbonyl complexes containing tetradentate Schiff bases

Several new hexa-coordinated ruthenium(II) complexes of the type [Ru(CO)(LL)(B)] (where, LL = anthacac, anthdibm, 2-amtpacac or 2-amtpdibm; B = PPh₃ or py or pip or morph) have been prepared by reacting [RuHCl(CO)(PPh₃)₃] or [RuHCl(CO)(PPh₃)₂(B)] with tetradentate Schiff bases such as bis(anthranilic acid)acetylacetimine (H₂-anthacac), bis(anthranilic acid) dibenzoylmethimine (H₂-anthdibm), bis(2-aminothiophenol) acetylacetimine (H₂-2-amptacac) or bis(2-aminothiophenol) dibenzoylmethimine (H₂-2-amtpdibm). The complexes have been characterised by elemental analyses and spectral (i.r., electronic spectra, ¹H- and ³¹P-n.m.r.) data. An octahedral structure has been tentatively proposed for the complexes, which were also tested for their antibacterial properties.     

Synthesis and characterization of manganese(II), nickel(II), copper(II) and zinc(II) Schiff-base complexes derived from 1,10-phenanthroline-2,9-dicarboxaldehyde and 2-mercaptoethylamine

The synthesis of a new Schiff base containing 1,10-phenanthroline-2,9-dicarboxaldehyde and 2-mercaptoethylamine is described. The reaction of 1,10-phenanthroline-2,9-dicarboxaldehyde with 2-mercaptoethylamine leads to 2,9-bis(2-ethanthiazolinyl)-1,10-phenanthroline (I) which undergoes rearrangement when reacted with manganese, nickel, copper or zinc ions to produce complexes of the tautomeric Schiff base 2,9-bis[2-(2-mercaptoethyl)-2-azaethene]-1,10-phenanthroline (L). The [M(L)Cl₂] complexes [where M = Mn(II), Ni(II), Cu(II) and Zn(II) ions] were characterized by physical and spectroscopic measurements which indicated that the ligand is a tetradentate N₄ chelating agent.     

Synthesis,characterization, and fluorescence properties of dinuclear cadmium(II) complexes

Four dinuclear cadmium(II) complexes, [Cd₂(L¹)(μ₂-Cl)Cl₂] (1), [Cd₂(L²)(μ₂-Cl)Cl₂] (2), [Cd₂(L³)(μ₂-Cl)Cl₂] (3), and [Cd₂(L⁴)₃ClO₄] (4), where HL¹ = 4-methyl-2,6-bis(1-(2-piperidinoethyl)iminomethyl)-phenol, HL² = 4-methyl-2,6-bis(1-(2-pyrrolidinoethyl)iminomethyl)-phenol, HL³ = 4-methyl-2,6-bis(1-(2-morpholinoethyl)iminomethyl)-phenol and HL⁴ = 4-methyl-2,6-bis(cyclohexylmethyl)iminomethyl)-phenol, were synthesized. They were characterized by elemental analysis, FT-IR, UV–Vis, fluorescence and electronspray ionization mass spectroscopy. Complexes 1 and 4 were also characterized by single crystal X-ray analysis. The cadmiums atoms in 1 are linked by μ₂-chloride in a distorted square pyramidal geometry, whereas cadmium atom in 4 is in a distorted octahedral environment. The complexes show emission bands around 500 nm with excitation at 395 nm.     

Coordination of di- and triimine ligands at ruthenium(II) and ruthenium(III) centers: structural,electrochemical and radical scavenging studies

Herein, we explore the coordination of di- and triimine chelators at ruthenium(II) and ruthenium(III) centers. The reactions of 2,6-bis-((4-tetrahydropyranimino)methyl)pyridine (thppy), N¹,N²-bis((3-chromone)methylene)benzene-1,2-diamine (chb), and tris-((1H-pyrrol-2-ylmethylene)ethane)amine (H₃pym) with trans-[Ru^IICl₂(PPh₃)₃] afforded the diamagnetic ruthenium(II) complex cis-[RuCl₂(thppy)(PPh₃)] (1) and the paramagnetic complexes [mer-Ru₂(μ-chb)Cl₆(PPh₃)₂] (2), and [Ru(pym)] (3), respectively. The complexes were characterized by IR, NMR, and UV–vis spectroscopy and molar conductivity measurements. The structures were confirmed by single crystal X-ray diffraction studies. The redox properties of the metal complexes were probed via cyclic- and squarewave voltammetry. Finally, the radical scavenging capabilities of the metal complexes towards the NO and 2,2-di(4-tert-octylphenyl)-1-picrylhydrazyl (DPPH) radicals were investigated     

Studies on the Synthesis and Potentiometric Properties of Three Novel Tripodal Ligands and their Complexes

Three novel tripodal ligands, N,N′,N′′-tri-(3′-phenylpropionic acid-2′-yl-)-1,3,5-triaminomethylbenzene (Ll), N,N′,N′′-tri-(4′-methylvaleric acid-2′-y1-)-1,3,5-triaminomethylbenzene (L2) and N,N′,N′′-tri-(3′methylvaleric acid-2′-yl-)-1,3,5-triaminomethylbenzene (L3), have been synthesized and fully characterized. The stabilizing ability of complexes of the three ligands with transition metal ions Cu(II), Ni(II), Zn(II) and Co(II) and rare earth metal ions La(III), Nd(III), Sm(III), Eu(III) and Gd(III) has been investigated by the pontentiometric method in water and in aqueous KNO₃ (0.1 mol dm⁻³) at 25.0±0.1 °C, respectively. The results show that there is a great deal of difference between two series of complexes’ stabilities. An explanation of the difference has been given.     

Oxomolybdenum(V) complexes of bis-(2-benzimidazolyl) alkanes

Summary Oxomolybdenum(V) complexes of the type (LH₄) [MoOCl₅] (where LH₂ = dimethylene bis-2-benzimidazole or tetramethylene bis-2-benzimidazole), [MoOCl₃(LH₂)] (where LH₂ = tetramethylene bis-2-benzimidazole), [(Mo₂O₄Cl₂-(H₂O)₃)₂(LH₂)] (where LH₂ = dimethylene bis-2-benzimidazole, tetramethylene bis-2-benzimidazole or hexamethylene bis-2-benzimidazole) and [Mo₂O₃Cl₄(LH₂)₂] (where LH₂ = tetramethylene bis-5-nitro-2-benzimidazole) were prepared and characterised. The mononuclear complexes show u.v.-vis. absorptions characteristic of octahedral molybdenum(V). The dinuclear complexes do not absorb in the visible region, possibly due to the presence of an Mo₂O ₄ ^{2 +}} core, which is also indicated by their diamagnetic behaviour. The biological activities of the free ligands and their complexes have been studied.     

Ruthenium(II) ligated to tetradentate diaminodithioethers: synthesis,characterisation and electrochemistry

Ruthenium(II) complexes containing two tetradentate ligands, 1,2-bis(o-aminophenylthio)ethane (L¹) and 1,2-(oaminophenylthio)xylene (L²), have been prepared. The complexes, which are of the type Ru(L)Cl₂ [L = L¹ (1);/L² (2)], [Ru(L)(PPh₃)Cl]Cl [L = L¹ (3); L² (4)] and [Ru(L)(bpy)](PF₆)₂ [L = L¹ (5);/L² (6)], were characterised by elemental analysis, i.r., u.v.-vis. and n.m.r. spectroscopy and their electrochemical behaviour has been examined by cyclic voltammetry using a glassy carbon working electrode and an Ag/AgCl electrode as the reference electrode. This revised version was published online in June 2006 with corrections to the Cover Date.     

Complexes of divalent transition metal chlorides with the tetradentate Schiff base ligand 1,2-bis(2′-pyridylmethyleneimino)-benzene

Summary Transition metal(II) chloro complexes of the new Schiff base ligand 1,2-bis(2-pyridylmethyleneimino)benzene (L), derived from 2-pyridinecarboxaldehyde and 1,2-phenylenediamine, were prepared. Compounds of [MnLCl₂]-H₂O, [CoLCl₂]·2H₂O, [NiLCl₂] and [Zn₃L₂Cl₄]Cl₂ were prepared. Details are given of the formation of the complex [Cu(L·EtOH)Cl₂], in which one molecule of EtOH adds across only one of the Schiff base {ie531-01} groups to give the coordinated ligand L·EtOH. The rationalization of this type of reaction by considering the steric requirements of the ligand is given. The complexes were characterized by elemental analyses, conductivity measurements, thermal techniques, mass spectra, magnetic susceptibilities and spectroscopic (i.r., ligand field, e.s.r., ¹H n.m.r.) studies. The nitrogen donor atoms of the tetradentate ligands L and L·EtOH are assumed to adopt an essentially planar arrangement about manganese(II), cobalt(II), nickel(II) and copper(II), with the remaining axial coordination sites occupied by chloro ligands to yield high-spin octahedral molecules. A trinuclear structure, based on tetrahedrally coordinated metal ions, is proposed for the zinc(II) complex.     

Trans-bis(dicyanamido)nickel(II) complexes with polyaza macrocyclic ligands

Two new trans-bis(dicyanamido)nickel(II) macrocyclic complexes, [Ni(II)(L1){N(CN)₂}₂] · H₂O (1) and [Ni(II)-(L3){N(CN)₂}₂] (2), where L1 is 3,10-bis(2-hydroxyethyl)-1,3,5,8,10,12-hexaazacyclotetradecane and L3 is 3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0^1.18,0^7.12]docosane, have been synthesized and structurally characterized by spectroscopic and X-ray crystallographic methods. In (1) and (2), each central nickel(II) ion possesses a distorted octahedral geometry with four equatorial nitrogen atoms from the macrocycle and two axial nitrogen atoms from dicyanamide anions, which are terminally bonded to the central nickel atom. The solid state electronic spectra of (1) and (2) using the diffuse reflectance method show a characteristic high-spin d⁸ nickel(II) ion in a distorted octahedral environment.