Transition metal complexes with a polydentate Schiff base derived from 3-formylsalicylic acid and 1,2-bis(o-aminophenylthio)ethane

The reaction of 3-formylsalicylic acid with 1,2-bis(o-aminophenylthio)ethane yielded a Schiff base with eight donor centres N₂S₂O₄ of which the inner compartment is of an N₂S₂O₂ type and the outer is of the O₂O₂ type. The base forms several mononuclear homo- and hetero-dinuclear complexes: e.g. mononuclear Cu^II, Ni^II and dinuclear Cu^II, Ni^II, UO₂ ^VI complexes. Hetero-dinuclear complexes {[M]M}, where M = the inner metal ion Cu^II, Ni^II and M = the outer metal ion Pd^II, UO₂ ^VI are also reported. The complexes were characterised by elemental analyses, spectral, thermal and magnetic measurements. Dicopper and dinickel complexes exhibit subnormal magnetic moments showing spin pairing between two metal centres, via the phenolato oxygen, whereas other mono-copper and mono-nickel complexes (both mononuclear and hetero-dinuclear) show the expected magnetic behaviour for 1e and 2e, respectively. The e.s.r. spectra of copper complexes also support the above behaviour.     

Synthesis,structural and catalytic activity of binaphthyl macrocyclic complexes

The binaphthyl macrocyclic ligand, N,N′-diethyl-[3,3′-(2,2′-dihydroxy-1,1′-binaphthyl)carboxamide]-2,2′-dihydroxy-1,1′-binaphthyl-3,3′-dicarboxylic acid (DDCDB), has been synthesized and investigated. The ligand (DDCDB) and its metal complexes involving Cu^II, Zn^II, UO ₂ ^II , Th^IV, Ce^III, Mo^VI and W^VI ions have been prepared and characterized by spectral (i.r., u.v.–vis.), elemental analyses, magnetic moments and thermal analyses measurements. DDCDB behaves as a tridentate ligand towards Cu^II, Zn^II and UO ₂ ^II ions coordinating via CO, NH and the deprotonated naphthyl OH groups in a ratio of 2:1 (M:L). On the other hand, DDCDB behaves in a bidentate manner coordinatingvia the NH and the deprotonated naphthyl OH groups only in case of the Th^IV, Ce^III, Mo^VI, and W^IV ions and in ratio 1:1 (M:L). Results of thermal measurements confirm the existence of solvent molecules inside and outside the coordination sphere. Th^VI complex has been applied for the hydrolysis of phosphodiester and the results show a significant rate enhancement of ~5.8 million fold with respect to the auto-hydrolysis of bis-(p-nitrophenyl) phosphate (BNPP) under the same conditions Also, Cu^II complex accelerates the photodegradation of the hazardous pollutant (acid green dye) in the presence of hydrogen peroxide by degrading 90% of the dye within 23 min.     

Complexes of N-phenyl-N′-2-furanthiocarbohydrazide with oxovanadium(IV), manganese(III), iron(III), cobalt(II), nickel(II), copper(II) and zinc(II)

A new ligand, N-phenyl-N -2-furanthiocarbohydrazide (HPhfth), and its complexes with VO^IV, Mn^III, Fe^III, Co^II, Ni^II, Cu^II and Zn^II have been prepared and characterized by elemental analyses, magnetic susceptibility measurements, i.r., n.m.r., u.v.–vis., mass and FAB mass spectral data. The room temperature e.s.r. spectra of the VO^IV, Fe^III and Cu^II complexes yield <g> values characteristic of square pyramidal VO^IV, octahedral Fe^III and square planar Cu^II, respectively. The Ni^II and Cu^II complexes semiconduct, but the Zn^II complex is an insulator at room temperature. However, the conductivity increases as the temperature increases from 303–383 K, with a band gap of 0.21–1.01 eV. HPhfth and its soluble complexes have been screened against several bacteria and fungi.     

Transition metal complexes derived from N-isonicotinamido-N′-benzoylthiocarbamide (H2IBTC)

Summary The synthesis and characterization of Cr^III, Mn^II, Fe^III, Co^II, Ni^II, Cu^II, Zn^II, Cd^II and UO _inf2 ^sup2+ complexes of N-isonicotinamido-_N-benzoylthiocarbamide (H₂IBTC) are reported. I.r. spectral data show that the ligand behaves in a bidentate, tridentate and/or tetradentate manner. Different stereochemistries are proposed for Cr^III, Mn^II, Fe^III, Co^II, Ni^II and Cu^II complexes on the basis of spectral and magnetic studies. The i.r. data indicate that the carbonyl oxygen of the benzoyl moiety is the backbone of chelation in most complexes.     

Ternary complexes of N-(2-acetamido)iminodiacetic acid and some aromatic acids. Isolation and stability constants in solution

Summary Ternary 1:1:1 complexes of Y^III, Co^II, Ni^II, Cu^II, La^III, Ce^III and UO ₂ ²⁺ with N-(2-acetamido)iminodiacetic acid (H₂ADA) as primary ligand and salicylic, anthranilic or phthalic acid as secondary ligand are described. The complexes of Co^II and Cu^II were isolated and characterized by microanalysis, molar conductance measurements, thermal analysis, i.r. and u.v.-vis. spectra. The formation constants of the 111 ternary complexes were determined potentiometrically in 20% (w/w) EtOH-H₂O at 24 °C. The stabilities of the 111 M ⁿ⁺ :ADA^2–:aromatic acid ternary complexes are higher than those of the corresponding 11 M ⁿ⁺ :aromatic acid binary complexes.     

Formate-driven catalysis and mechanism of an iridium–copper complex for selective aerobic oxidation of aromatic olefins in water

A hetero-dinuclear Ir^III–Cu^II complex with two adjacent sites was employed as a catalyst for the aerobic oxidation of aromatic olefins driven by formate in water. An Ir^III–H intermediate, generated through formate dehydrogenation, was revealed to activate terminal aromatic olefins to afford an Ir-alkyl species, and the process was promoted by a hydrophobic [Ir^III–H]-[substrate aromatic ring] interaction in water. The Ir-alkyl species subsequently reacted with dioxygen to yield corresponding methyl ketones and was promoted by the presence of the Cu^II moiety under acidic conditions. The Ir^III–Cu^II complex exhibited cooperative catalysis in the selective aerobic oxidation of olefins to corresponding methyl ketones, as evidenced by no reactivities observed from the corresponding mononuclear Ir^III and Cu^II complexes, as the individual components of the Ir^III–Cu^II complex. The reaction mechanism afforded by the Ir^III–Cu^II complex in the aerobic oxidation was disclosed by a combination of spectroscopic detection of reaction intermediates, kinetic analysis, and theoretical calculations.

A hetero-dinuclear Ir^III–Cu^II complex with two adjacent sites was employed as a catalyst for the aerobic oxidation of aromatic olefins driven by formate and promoted by a hydrophobic interaction in water.     

Metal chelates with some cellulose derivatives; part IV. Structural chemistry of HEC complexes

Reactions of hydroxyethyl cellulose (HEC) with Cr ^III, Ni^II, Co^II, or Cu^II chlorides in aqueous medium yielded complexes with formulae [M(HEC)Cl _m .n H ₂O], wherem =1 or 2 and n=2 or 3. HEC acted as a uninegatively charged bidentate ligand in the case of Cr^III and Ni^II, and as a neutral ligand in the case of Co^II and Cu^II complexes. The spectra showed that the binding sites in Cr^III and Ni^II complexes were the ether oxygen between two ethoxyl groups and the oxygen of the hydroxyl group; while in the Co^II and Cu^II complexes the binding sites were the oxygen of ethoxyl groups and the primary alcoholic O atom of glucopyranose rings. These complexes would most likely exhibit octahedral geometry with Cr^III, Ni^II, and Co^II, but square planar configuration in the case of the Cu^II complex. The ligand parameters of the Cr^III, Ni^II, and Co^II metal chelates were calculated in different solvents and at different temperatures. The thermal stability of the above complexes was investigated and the overall thermodynamics functions G⁰, H⁰, and S⁰, associated with complex formation, were estimated.     

Novel asymmetric heterobimetallic complexes of transition metals and the kinetics of oxygen binding to a cobalt(II) complex

A series of asymmetric heterobimetallic complexes of the type [LMLSn]Cl and [LMLSn]Cl₂, where L = ethylene diamine, M = Mn^II, Co^II, Ni^II and Cu^II, M = Cr^III and Fe^III and L = 1-tryptophan and 1-valine, have been synthesized and characterized by elemental analyses, u.v.–vis., i.r., e.p.r., n.m.r., cyclic voltammetry and conductivity measurements. The Co^III analogue of these complexes was characterized by two dimensional n.m.r. COSY data. The kinetics of oxygen binding with the complex [C₁₅H₂₃N₄O₂SnCo]Cl has also been studied. The kinetic data proves that Co^II of a coordinated molecule participates in the rate-determining step of the dioxygen binding process. The plots of the pseudo-first-order rate k _obs versus [O₂] are linear passing through an intercept. The electrochemical behaviour of [C₁₅H₂₃N₄O₂SnCo]²⁺ and [C₁₅H₂₃N₄O₂SnCu]⁺ was monitored by cyclic voltammetry. Comparison of the electrochemical properties of [Co^IIISn^IV]²⁺ and [Cu^IISn^IV]⁺ reveal that, in both the species, one electron transfer reaction takes place. For the [Co^IIISn^IV]²⁺ species E ⁰ = 0.272 and –1.1 V and for the [Cu^IISn^IV]⁺ species E ⁰ = 0.078 and –0.300 V values were obtained, respectively.     

New bis-macrocyclic complexes with transition metal ions

Template condensation of benzidine, formaldehyde, ethylenediamine or 1,3-diaminopropane, metal salt and 1-phenyl-1,3-butanedione or 2,3-butanedione in a 1:4:2:2 molar ratio results in the formation of two new series of binuclear pentaaza macrocyclic complexes: dichloro[1,1-phenylbis(7-methyl-9-phenyl-1,3,6,10,13-pentaazacyclotetradeca-6,9-diene) metal(II)], [M₂LCl₄] (M = Co^II, Cu^II, Fe^III and Zn^II) and dichloro[1,1-phenylbis(8,9-dimethyl-1,3,7,10,14-pentaazacyclopentadeca-7,9-diene) metal(II)], [M₂LCl₄] (M = Ni^II, Co^II, Cu^II and Cd^II). Both series were characterized by i.r., ¹H-n.m.r., u.v.–vis. spectral studies, conductivity and magnetic susceptibility measurements.     

N-Phthaloylglycinate ternary complexes with cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) metal ions and aromatic mono,bi and tridentate amines

Complexes of N-phthaloylglycinate (N-phthgly) and Co^II, Ni^II, Cu^II, Zn^II and Cd^II containing imidazole (imi), N-methylimidazole (mimi), 2,2-bipyridyl (bipy) and 1,10-phenanthroline (phen), and tridentate amines such as 2,2,2-terpyridine (terpy) and 2,4,6-(2-pyridyl)s-triazine (tptz), were prepared and characterized by conventional methods, i.r. spectra and by thermogravimetric analysis. For imi and mimi ternary complexes, the general formula [M(imi/mimi)₂(N-phthgly)₂]·nH₂O, where M = Co^II, Ni^II, Cu^II and Zn^II applies. For Cd^II ternary complexes with imi, [Cd(imi)₃(N-phthgly)₂]·2H₂O applies. For the bi and tridentate ligands, ternary complexes of the formula [M(L)(N-phthgly)₂]·nH₂O were obtained, where M = Co^II, Ni^II, Cu^II and Zn^II; L = bipy, phen, tptz and terpy. In all complexes, N-phthgly acts as a monodentate ligand, coordinating metal ions through the carboxylate oxygen, except for the ternary complexes of Co^II, Ni^II and Cu^II with mimi and Cu^II and Zn^II with imi, where the N-phthgly acts as a bidentate ligand, coordinating the metal ions through both carboxylate oxygen atoms.     

Complexes of iron(II), iron(III) and zinc(II) with condensation derivatives of 2-acetylpyridine and oxalic or malonic dihydrazide. Crystal structure of tris[(1-(2-pyridyl)ethylidene)hydrazine]iron(II) perchlorate

Complexes of zinc and iron with N, N²-bis[(1E)-1-(2-pyridyl)ethylidene]ethanedihydrazide (H₂L1) and N ,N²-bis[(1E)-1-(2-pyridyl)ethylidene]propanedihydrazide (H₂L2) were prepared. Zn^II complexes with both ligands have an octahedral geometry. In the complex of Zn^II with H₂L1, the ligand is coordinated as a tridentate species in the monoanionic form, building two five-membered rings around Zn^II. Three remaining coordination sites are occupied by water molecules, and in the outer sphere there is a ClO ₄^– ion. In the other Zn^II complex, the H₂L2 ligand is coordinated in the enol form as a tetradenate species, forming a five-memebered, a six-membered and a seven-membered ring, the remaining coordination sites being occupied by water molecules, while in the outer sphere there are two ClO ₄^– ions. The Fe^III complex with H₂L2 is a high-spin octahedral complex. The ligand is coordinated in the enol form, in a tetradentate fashion via pyridine and hydrazone nitrogens. The remaining two coordination sites in the complex are occupied by water molecules and a Cl^– ion, and in the outer sphere there are two Cl^– anions. The octahedral Fe^III complex obtained from the reaction of FeCl₃·6H₂O and H₂L1 in absolute ethanol has the formula [Fe(HL1)Cl₂(H₂O)]·1.5H₂O. However, during coordination of the H₂L1 ligand to Fe^III in water, oxidative degradation of the side chain (–CO–CO–) and reduction of Fe^III to Fe^II occurs, affording octahedral tris(1-(2-pyridyl)ethylidenehydrazine] iron^II perchlorate, as confirmed by X-ray structure analysis.     

Cation Coordination of Bisamidopyridine-derived Receptors as Investigated in the Solid-state and in Solution

A bisamidopyridine-type receptor, N,N′-bis(6-methyl-2-pyridyl)pyridine-2,6-dicarboxamide (1), and its Co^III complex were prepared and their X-ray structures were compared to those of N,N′-diphenylpyridine-2,6-dicarboxamide (2) and Co^III(2)². Introduction of the two additional coordinative groups resulted in second-order interactions between the central ion and the nitrogen atoms of the terminal pyridine moieties in the crystalline state. Solution studies in acetonitrile revealed the importance of these interactions for the ligand's metal ion recognition ability. Whereas 2 only binds to Pb^II and Cu^II, 1 yields complexes with a majority of the heavy and transition metal ions studied, Co^II, Ni^II, Cu^II, Zn^II, Fe^III, Fe^II, Hg^II, and Pb^II, respectively. The cation binding properties in solution were investigated by absorption spectroscopy and in the case of 1–M^II/III, the formation of two spectroscopically distinguishable types of complexes was found. Protonation experiments and theoretical considerations helped to gain further insight into possible modes of coordination in solution.     

Metallomicellar Catalytic Hydrolysis of NPP by CuIINiII Heterodinuclear Complexes Containing Diamine Groups in Brij35 Micellar Solution

The hydrolysis of p‐nitrophenyl phosphate (NPP) catalyzed by metallomicelles formed from four asymmetry Cu^IINi^II heterodinuclear oxamido‐bridged complexes, whose ligands contain different diamine groups, and nonionic surfactant Brij35 has been investigated quantitatively at the pH range of 6.0–10.5 and 25°C, respectively. The results indicated that the rates of catalytic hydrolysis of NPP by four complexes in Brij35 micellar solution were all largely enhanced under the experimental conditions. The order of effectiveness of the four complexes in Brij35 micellar solutions toward hydrolysis of NPP was found to be: complex I>complex II>complex III>complex IV. The different catalytic function of four complexes may be attributed to the different activation abilities of coordinated water molecules induced by different polarities of ligands, which has been discussed in detail. Meanwhile, kinetic studies show that the active species in the catalytic hydrolysis of NPP may be the aquo‐hydroxy form and that the mechanism of the reaction involves intramolecular nucleophilic attack of the nickel‐bound hydroxide ion on phosphoryl of NPP. The studies suggested that the metallomicelle containing Cu^IINi^II heterodinuclear oxamido‐bridged complexes with two coordinated H₂O molecules may be a potential catalyst for the hydrolysis of NPP.     

Synthese,Struktur und EPR‐Untersuchungen von binuklearen Bis(N,N,N‴,N‴‐tetraisobutyl‐N′,N″‐isophthaloylbis(thioureato))‐Komplexen des CuII,NiII, ZnII,CdII und PdII

Synthesis, Structure and EPR Investigations of binuclear Bis(N,N,N?,N?‐tetraisobutyl‐N′,N″‐isophthaloylbis(thioureato)) Complexes of Cu^II, Ni^II, Zn^II, Cd^II and Pd^II The synthesis of binuclear Cu^II‐, Ni^II‐, Zn^II‐, Cd^II‐ and Pd^II‐complexes of the quadridentate ligand N,N,N?,N?‐tetraisobutyl‐N′,N″‐isophthaloylbis(thiourea) and the crystal structures of the Cu^II‐ and Ni^II‐complexes are reported. The Cu^II‐complex crystallizes in two polymorphic modifications: triclinic, (Z = 1) and monoclinic, P2₁/c (Z = 2). The Ni^II‐complex was found to be isostructural with the triclinic modification of the copper complex. The also prepared Pd^II‐, Zn^II‐ and Cd^II‐complexes could not be characterized by X‐ray analysis. However, EPR studies of diamagnetically diluted Cu^II/Pd^II‐ and Cu^II/Zn^II‐powders show axially‐symmetric g and A ^Cu tensors suggesting a nearly planar co‐ordination within the binuclear host complexes. Diamagnetically diluted Cu^II/Cd^II powder samples could not be prepared. In the EPR spectra of the pure binuclear Cu^II‐complex exchange‐coupled Cu^II‐Cu^II pairs were observed. According to the large Cu^II‐Cu^II distance of about 7,50Å a small fine structure parameter D = 26·10^?4 cm^?1 is observed; T‐dependent EPR measurements down to 5 K reveal small antiferromagnetic interactions for the Cu^II‐Cu^II dimer. Besides of the dimer in the EPR spectra the signals of a mononuclear Cu^II species are observed whose concentration is T‐dependent. This observation can be explained assuming an equilibrium between the binuclear Cu^II‐complex (Cu^II‐Cu^II pairs) and oligomeric complexes with “isolated” Cu^II ions.     

Ambidenticity of a tridentate oxygen-nitrogen donor towards bivalent and trivalent transition metal ions

Summary N-salicylidene anthranilamide (H₂SAA) and its Cr^III, Mn^II, Fe^III, Co^II, Ni^II and Cu^II complexes were prepared and characterized by physicochemical and spectroscopic data. H₂SAA enolizes to give a dibasic ONO donor set in the divalent metal complexes. It also binds to the trivalent metal ions in a nonenolized form using a monobasic ONN donor set. Co^II is oxidized to Co^III during complexation. Octahedral geometries are proposed for Cr^III, Mn^II, Fe^III and Co^III complexes, while square planar geometries are suggested for the Ni^II and Cu^II complexes. Phenoxide bridging in the Cr^III and Fe^III complexes and enoxide bridging in the Ni^II and Cu^II complexes is proposed.     

Synthesis of new 14- and 16-membered macrocycles and their transition metal complexes

Summary Benzoylacetic acid (1 mol) interacts with ethylenediamine or with propanediamine (2 mol) to yield new N₄ macrocycles 1,5,8,12-tetraazacyclotetradeca-2,4,9,11-tetraphenyl-3, 10-dicarboxylic-4,11-diacetic acid- 1,8-diene (L¹) and 1,5,9,13-tetraazacyclohexadeca-2,4,10,12-tetraphenyl-3, 11-dicarboxylic-4,12-diacetic acid-1,9-diene (L²), respectively. These macrocycles have been successfully complexed with Cr^III, Fe^III, Mn^II, Co^II, Ni^II, Cu^II and Zn^II. The complexes of the divalent metal ions are non-electrolytes, while those of Fe^III and Cr^III are 1:1 electrolytes in DMSO. On the basis of ligand field spectra and magnetic moments an octahedral geometry has been proposed for all the complexes.     

Catalytic cleavage of p-nitrophenyl picolinate by metallomicelles made up of copper(II) complexes of small molecular ligands bearing hydroxyl or carboxyl groups

The esterolytic activities of Cu²⁺ complexes (Cu²⁺L1, Cu²⁺L2 and Cu²⁺L3) of three small molecular ligands: N-(2-hydroxyethyl)ethylenediamine (L1), 2,2-iminodiethanol (L2) and iminodiacetic acid (L3), in the presence of the nonionic micelle (Brij35) towards the substrate p-nitrophenyl picolinate (PNPP) have been investigated. The catalytic reactivity order is: Cu²⁺L1 > Cu²⁺L2 > Cu²⁺L3, which can be attributed to the similarity of and the difference between their catalytic mechanisms, most likely resulting from the analogy and the discrepancy of the structure of the three complexes. The critical feature of the catalytic process is, quite likely, the formation of a ternary complex involving a binary metal ion complex and the substrate, followed by pseudo-intramolecular nucleophilic attack of the alcoholic hydroxyl (for Cu²⁺L1 and Cu²⁺L2) or metal ion bound hydroxide ion (for Cu²⁺L3), at carbonyl of the substrate. Detailed kinetic analyses are given for the hydrolysis of PNPP catalyzed by the three complexes.     

Synthesis,spectral and redox properties of metal complexes of macrocyclic tetraaza chiral Schiff bases

New transition metal(II) coordination compounds of tetraaza macrocyclic chiral Schiff bases, derived from 2-hydroxybenzylideneacetylacetone or 4-hydroxybenzylideneacetylacetone and (1R, 2R)-(–)-1,2-diaminocyclohexane, have been prepared and characterised spectroscopically and electrochemically. E.p.r. spectral data for the Cu^II complexes reveal a strong metal-to-ligand -interaction in their square-planar configuration and the broadening of the g component is due to the strain created by 1R and 2R groups in the cyclohexane rings. The cyclic voltammetric (c.v.) data of the copper complexes show an unusual oxidation state of Cu^III, while Co^II complexes show a reversible Co^II/Co^III redox peak along with an additional peak in the negative potential region characteristic of reversibly bound oxygen. The c.v. results reveal that both Cu^II and Co^II complexes bind axially with added bases. The spectroscopic results reveal that copper, cobalt and nickel complexes are in square-planar geometry, whereas manganese is in octahedral geometry.     

Synthesis and characterization of new 13 and 14-membered macrocycles and their transition metal complexes

Two new macrocyclic ligands 1,4,7,9,12-pentaaza-10,11-dioxo-8,9,12,13-bis-(1-oxo-3-thio-2-hydropyrimidine)-trideca-7,13-diene, (L¹) and 1,4,7,9,12-pentaaza-10,12-dioxo-8,9,13,14-bis-(1-oxo-3-thio-2-hydropyrimidine)-tetradeca-7,14-diene, (L²) and their complexes with Cr^III, Mn^II, Fe^III, Co^II, Ni^II, Cu^II and Zn^II have been synthesized, and characterized by elemental analysis, i.r., ¹H-n.m.r., e.p.r., u.v.–vis. spectroscopy, magnetic susceptibility and conductance measurements. The conductivity measurements suggest that the complexes of divalent metal ions are 1:1 electrolytes whereas the trivalent metal ions are non-electrolytes. On the basis of electronic spectra and magnetic moment measurements the Cr^III and Fe^III complexes are octahedral, while the divalent metal complexes are tetrahedral except for the Ni^II and Cu^II complexes which are proposed to have square planar geometry. All the ligands and their complexes have been screened against gram-positive bacteria Staphylococcus aureus and gram-negative bacteria E. coli. The results show that they inhibit the growth of bacteria.     

Ligational behaviour ofN-benzamido-N′-benzoylthiocarbamide (HBBTC) towards transition metal ions

Summary Complexes ofN-benzamido-N-benzoyl-thiocarbamide (HBBTC) with Co^II, Ni^II, Cu^II, Zn^II, Cd^II and UO ₂ ²⁺ have been prepared and characterized on the basis of elemental analyses, molar conductance, magnetic moment and spectral (visible, i.r.) studies. I.r. spectra show that HBBTC behaves in a bidentate and/or tridentate manner. Different stereochemistries are proposed for Co^II, Ni^II and Cu^II complexes on the basis of spectral and magnetic studies.