Synthesis,characterization and SOD-like activities of manganese-containing complexes with N,N,N′,N′-tetrakis(2′-benzimidazolyl methyl)-1,2-ethanediamine (EDTB)

A series of manganese-containing mononuclear and binuclear model compounds of superoxide dismutase (SOD) coordinated by a polydentate ligand N,N,N′,N′-tetrakis(2′-benzimidazolyl methyl)-1,2-ethanediamine (EDTB) have been synthesized and characterized. The SOD-like activities of these complexes have been measured by means of modified nitroblue tetrazolium (NBT) photoreduction, and the rate constants k_Q of catalytic superoxide dismutation are in the range 6.96×10⁶–2.32×10⁷ l mol⁻¹ s⁻¹. In complex [Mn(EDTB)(Ac)](Ac)·C₂H₅OH the coordination environment around the manganese(II) ion can be described as a highly-distorted capped octahedron with an oxygen atom of the bidentate acetate ion at the capping site. This complex is the first example in which EDTB acts as a pentadentate ligand with one non-ligating benzimidazole group.     

Synthesis and crystal structures of Zn(II) complexes with N,N′-bis[(1-(2-pyridyl)ethylidene)propane-1,3-diamine and N,N′-bis[(1-(2-Pyridyl)ethylidene)ethane-1,2-diamine1

Two new zinc complexes, [Zn(Ppd)I]ClO₄ (I) and [Zn(Ped)I]ClO₄ (II), where Ppd and Ped are the Schiff bases N,N??-bis[(1-(2-pyridyl)ethylidene)propane-1,3-diamine and N,N??-bis[(1-(2-pyridyl)ethylidene)ethane-1,2-diamine, respectively, have been synthesized and characterized by means of elemental analysis, infrared spectroscopic, molar conductivity, and single crystal X-ray diffraction. The crystal of I is tri-clinic: space group $P\bar 1$ a = 8.421(2), b = 9.143(2), c = 13.166(3) ?, ?? = 92.521(5)°, ?? = 94.498(3)°, ?? = 94.232(4)°, V = 1006.6(4) ?³, Z = 2. The crystal of II is triclinic: space group $P\bar 1$ , a = 8.219(1), b = 8.483(1), c = 14.733(2) ?, ?? = 80.058(1)°, ?? = 81.960(1)°, ?? = 89.300(1)°, V = 1001.8(2) ?³, Z = 2. The zinc atom in the complexes assumes a distorted square pyramidal geometry through coordination by two pyridine N atoms and two imine N atoms of the Schiff base at the basal plane, and by a I atom at the apical position.     

Spectroscopy and stereochemistry of the optically active copper(II), cobalt(II) and nickel(II) complexes with Schiff bases N,N′-(1R,2R)-(−)-1,2-cyclohexylenebis(3-methylbenzylideneiminato) and N,N′-(1R,2R)-(−)-1,2-cyclohexylenebis(5-methylbenzylideneiminato)

Schiff bases obtained from N,N′-(1R,2R)-1,2-cyclohexanediamine and 2-hydroxy-3-methylbenzaldehyde, 2-hydroxy-5-methylbenzaldehyde, have been used as ligands for copper(II), cobalt(II) and nickel(II). The complexes were characterized with UV–Vis, circular dichroism (CD), infrared, diamagnetic and paramagnetic ¹H NMR spectroscopy. CD spectra revealed exciton coupled π→π* transitions. Assignments of LMCT and d–d transitions in CD spectra of Ni(II), Co(II) and Cu(II) complexes is proposed. CD data are characteristic for central ion tetrahedral distortion from the planarity and λ conformation of the cyclohexane ring. ¹H NMR of Ni(II) complexes exhibited significant coordination shifts of CHN and ring protons which are in the closest proximity to Ni(II). The ¹H NMR paramagnetic spectra of Co(II) complexes revealed the most upfield shifted resonance at −60 ppm assigned to CHN and −28 ppm to hydrogen atom at C(5′) of the phenyl ring. Results of spectral analyses suggest central ions in a distorted square-planar geometry with N₂O₂ chromofore group.     

Features of the reactions of β-aryl(heteryl)-α-nitroacrylates with N,N-, N,O-, and N,S-binucleophiles

The reactions of ??-aryl(heteryl)-??-nitroacrylates with N,N-, N,O-, and N,S-binucleophiles proceed regiospecifically through the initial formation of the Ad_N products, among which only the product from o-aminothiophenol was isolated. The conditions of converting the S-adducts into 2-aryl(heteryl)benzothiazole were found. The N-adducts formed in the reaction with hydrazine, o-phenylenediamine, and o-aminophenol undergo immediately the spontaneous transformation into the linear (azine, azomethine) or heterocyclic (benzimidazole) structures.     

N,N′-(1,2-phenylene)bis­(pyridine-2-carboxamide) and N,N′-(1,2-cyclohexanediyl)bis(pyridine-2-carbox­amide) toluene hemisolvate

The crystal structures of N,N′-(1,2-phenyl­ene)­bis­(pyridine-2-carbox­amide), C₁₈H₁₄N₄O₂, (I), and N,N′-(1,2-cyclo­hexane­diyl)­bis­(pyridine-2-carbox­amide) have been determined, the latter compound as the toluene hemisolvate, C₁₈H₂₀N₄O₂·0.5C₇H₈, (II). In (I), the benzene ring is nearly coplanar with one of the pyridine rings and forms a dihedral angle of 59.4 (1)° with the other. However, in (II), the dihedral angle of the two pyridine rings is 70.0 (1)°.     

Synthesis,characterization, and structures of copper(I) complexes with N,N′-bis[1-(4-chlorophenyl)ethylidene]ethane-1,2-diamine and N,N′-bis[1-(4-nitrophenyl)ethylidene]ethane-1,2-diamine

Two ligands, N,N′-bis[1-(4-chlorophenyl)ethylidene]ethane-1,2-diamine (L¹ ) and N,N′-bis- [1-(4-nitrophenyl)ethylidene]ethane-1,2-diamine (L² ) and their corresponding copper(I) complexes, [Cu(L ¹)₂]ClO₄ (1) and [Cu(L ²)₂]ClO₄ (2), have been synthesized and characterized by CHN analyses, ¹H-NMR, IR, and UV–Vis spectroscopy. The crystal structures of L¹ and [Cu(L ¹)₂]ClO₄ (1) were determined from single crystal X-ray diffraction. L¹ lies across a crystallographic inversion center and the C=N is approximately coplanar with the benzene ring and adopts E configuration. The coordination polyhedron about copper(I) in 1 is best described as a distorted tetrahedron. Quasireversible redox behavior is observed for the complexes.     

Synthesis and Crystal Structure of a N,N,N′-tri(2-hydroxy-5-methylbenzyl)-1,2-ethanediamine

An aminophenol ligand, N,N,N′-tri(2-hydroxy-5-methylbenzyl)-1,2-ethanediamine, was prepared through the Mannich reaction, and structurally characterized by NMR, IR, MS and single-crystal X-ray diffraction. The title compound (C26H32N2O3, Mr = 420.54) belongs to the monoclinic system, space group P21/n with a = 8.6233(14), b = 10.2655(16), c = 26.017(4) ′, β = 95.797(2)o, V = 2291.3(6) ′3, Z = 4, the final R = 0.0461 and wR = 0.1139 for 4267 unique reflections (Rint = 0.028) with 11691 observed ones (I > 2σ(I)).     

Electrochemical and electrocatalytic studies of the N,N′-(1R,2R)-(–)-1,2-cyclohexylenebis(salicylideneiminato)cobalt(II) complex

The electrochemical properties and catalytic activity of a Co(II) complex with the optically active Schiff base derived from (1R,2R)-(–)-cyclohexanediamine and salicylaldehyde have been studied in non-aqueous solutions. When dissolved in deoxygenated non-aqueous solutions, the complex exhibits reversible redox properties for the Co(II)/Co(III) couple. Electrochemical reduction of oxygen and oxidation of cobalt(II) was observed on cyclic voltammograms of solutions containing both dioxygen and the Schiff base-cobalt(II) complex. An anodically formed film on a platinum electrode, studied by means of X-ray photoelectron spectroscopy, revealed the presence of the oxidized Co(III) species. Cyclic voltammetry of oxygenated solutions examined after a period of time indicates an electrochemical activity of coordinated superoxo/peroxo species in the 0.7–1.1 V potential range. In the presence of 4-methyl-1-cyclohexene the cyclic voltammetry curves reveal changes similar to those caused by the removal of oxygen. The GC-MS technique was used to identify some of the products formed by the catalytic oxidation of cyclohexene and 4-methyl-1-cyclohexene. Electronic Publication     

Synthesis,acid-base and complexing properties of N,N,N′,N′-tetrakis(O-butylhydroxyphosphorylmethyl)-1,2-diaminoethane

Russian Journal of General Chemistry - A method of synthesis of organophosphorus analog of ethylenediaminetetraacetic acid (a common complexon),...     

Interaction of calf thymus DNA with N,N′-Bis(3,4-dihydroxybenzylidene)-1,2-diaminobenzene ligands

In the present study, at first, N,N′-bis(3,4-dihydroxyhenzylidene)-1,2-diaminobenzene (BDBDAB), has been synthesized by combination of 1,2-diaminobenzene and 3,4-dihydroxybenzaldehyde in a solvent system. These ligand containing ortho-quinone functional groups were characterized using UV-VIS and IR spectroscopies. Subsequently, the interaction between native calf thymus deoxyribonucleic acid (ct-DNA) and BDBDAB was investigated in 10 mM Tris-HCl buffer solution, pH 7.2, using UV-visible absorption and fluorescence spectroscopies, thermal denaturation technique, viscosity measurement, and cyclic voltametry. From spectrophotometric titration experiments, the binding constants of BDBDAB with double stranded DNA were found to be (0.9 ± 0.1) × 10⁴ M⁻¹. The magnitude of the interaction between the ligands and DNA can be quantified by using the Stern-Volmer equation. From the plot of I ₀/I versus [DNA]/[BDBDAB] the quenching constants (K _SV) were obtained and found to be 5.6 ± 0.2. Thermal denaturation experiments represent the increasing of melting temperature of DNA (about 3.2°C) due to binding of BDBDAB. There is no increasing of viscosity was observed in addition of BDBDAB to DNA. The electroactivity of the quinone moiety in N,N′-bis(3,4-dihydroxybenzylidene)-1,2-diaminobenzene bound to DNA could be employed as cyclic voltametry to obtain binding constant. These results suggest that interaction with the grooves could be the principal mode of binding of BDBDAB to double stranded ct-DNA.     

Synthesis and structural features of copper(II) complexes of N,N,N′,N′-tetramethylethylenediamine with 2-chlorobenzoate1− and 2-hydroxybenzoate1−

Abstract

Two copper(II) coordination complexes, formulated as [Cu(tmen)(Clba)₂] (1) and [Cu(tmen)(Hsal)₂·H₂O] (2) (where tmen?=?N,N,N′,N′-tetramethyl ethylenediamine (C₆H₁₆N₂), Clba^1? = 2-chlorobenzoate (C₇H₄ClO₂^1?), and Hsal^1? (C₇H₅O₃^1? = monoanion of o-hydroxybenzoic acid (salicylic acid)), have been synthesized and characterized by elemental combustion analysis, spectroscopic techniques, thermal studies, and single crystal X-ray analyses. Complex 1 consists of two distinct monomeric units in which the coordination environment around the central copper(II) ion is a distorted octahedron with a CuN₂O₄ chromophore, constituted by a chelating tmen molecule, and two 2-chlorobenzoate^1? anions coordinated through their carboxylate-O atoms in an asymmetrical bidentate fashion. Complex 2 is also a monomer and consists of an CuN₂O₃ chromophore, in which tmen is coordinated to Cu(II) through its two N atoms in a chelating bidentate fashion, and an aqua-O and the two o-hydroxybenzoate^1? (HSal^1?) anions are coordinated through one of their carboxylate-O atoms in a monodentate mode, forming a square pyramidal structure. Hydrogen bonding interactions especially of O–H…O, N–H…O, and C–H…Cl types interweave monomeric units and stabilize the overall crystal structures in both complexes. Thermal analysis and antibacterial activities of 1 and 2 against various bacterial strains were also investigated.     

Tricarbonylrhenium(I) bromide complexes with N,N′-bis[1-(4-chlorophenyl)ethylidene]ethane-1,2-diamine and N,N′-bis[1-(4-nitrophenyl)ethylidene]ethane-1,2-diamine–syntheses,structures, electrochemical and spectroscopic studies

Two rhenium(I) complexes, [Re(CO)₃Br(L ⁿ )] (n = 1, 2), (L¹= N,N′-bis[1-(4-chlorophenyl)ethylidene]ethane-1,2-diamine and L² = N,N′-bis[1-(4-nitrophenyl)ethylidene]ethane-1,2-diamine) have been synthesized and characterized by CHN analyses, ¹H NMR, IR, and UV-Vis spectroscopy. The molecular structure of [Re(CO)₃Br(L¹)] is a distorted octahedron around rhenium with one Br, facial arrangement of three CO's, and one diimine. The UV-Vis spectra of the complexes have metal-to-ligand charge transfer bands increasing in wavelength when the L² ligand is replaced by L¹, in agreement with the oxidation potential of the complexes.     

Complexation of (1Z, 2Z)- N ′-1-, N ′-2-dihydroxy- N -1-, N -2-dipyridin-2-ylethanedimidamide in mono and dinuclear Zn(II), Cd(II), Hg(II) and Sn(IV) complexes

Mononuclear O,O-coordinated complexes K₂(MLCl₂) M = Zn(II), Cd(II) and dinuclear complexes (MZnLCl₂R₂)^x along with dinuclear N,N-coordinated complexes (M′ZnH₂LCl₂R₂)^y (where M = Zn(II), Cd(II), Hg(II) and M′ = M and Sn(IV); R = Cl, CH₃; x = 0, ?2; y = 0, +2) of N′-1-,N′-2-dihydroxy-N-1-,N-2-dipyridin-2-ylethanedimidamide (H₂L) have been prepared. All complexes have been characterized by ¹H NMR, IR, EI-mass spectroscopy and elemental microanalysis. These results are in agreement with our prediction for structures of mono and dinuclear complexes of H₂L and L^?2 with Zn(II) in the gas phase by theoretical studies.     

Preparation of N,N,N′-tris(trimethylsilyl)amidines; a convenient route to unsubstituted amidines

The tris(trimethylsilyl)amidines RC(NSiMe₃)N(SiMe₃)₂ (R  C₆H₅, p-CH₃C₆-H₄, p-ClC₆H₄, p-MeOC₆H₄, p-Me₂NC₆H₄, p-CF₃C₆H₄, p-C₆H₅C₆H₄ and CF₃) are prepared by the reaction of the respective nitriles with (Me₃Si)₂NLi·OEt₂ in ether to give intermediates RC(NLi)N(SiMe₃)₂. Heating these intermediates with ClSiMe₃ in toluene affords the products, which are isolated by vacuum distillation, in high yield. With 1,4-dicyanobenzene, two equivalents of reagents affords the per(trimethylsilyl)-1,4-diamidine. Hydrolysis of the intermediates with 6N ethanolic HCl affords the unsubstituted amidine hydrochlorides RC(NH)NH₂·HCl (R  C₆-H₅, p-MeOCh₆H₄, p-ClC₆H₄, p-O₂NC₆H₄) in high yield.     

A New Application of N,N ′-dibromo-N,N ′–1,2-ethanediylbis(p-toluenesulfonamide) as Selective and Efficient Reagent for the Oxidation of Various Thiols to Disulfides

ABSTRACT

An efficient method for oxidation of thiol to their corresponding disulfides in high yields with N, N^′-Dibromo-N,N^′–1,2-ethanediyl bis (p-toluensulphonamide) in dichloromethane at room temperature is described.     

Spectroscopic and extraction studies of new transition metal complexes with N,N ′- bis (2-aminothiophenol)-1, 4- bis (2-carboxaldehydephenoxy)butane

Metal complexes of La(III), Cu(II) and Ni(II) with a thio Schiff base derived from 1,4-bis(2-carboxaldehydephenoxy)butane and 2-aminothiophenol have been synthesized in absolute ethanol and characterized by microanalytical data, magnetic measurements, ¹H NMR, ¹³C NMR, UV-visible, IR-spectra, mass spectra and conductance measurements. The extractability of divalent cations was evaluated as a function of relationship between distribution ratios of the metal and pH or ligand concentration. The highest extraction percentage of Cu⁺² and Ni⁺² were at pH 7.0 and 6.4, respectively. The ligand can effectively be used in solvent extraction of copper(II) and nickel(II) from aqueous phase to organic phase.     

Lanthanide Complexes with N,N′-Bis(2- hydroxybenzylidene)-2-hydroxyphenylmethanediamine

Complexes of lanthanides with N,N-bis(2-hydroxybenzylidene)-2-hydroxyphenylmethanediamine (H₃L) were synthesized and investigated by the elemental, IR, magnetochemical, and thermogravimetric methods. Using the data obtained, they were found to have compositions Ln₂L₂ · nH₂O and La₂L₂ · MCl₂ · 4H₂O (Ln = La³⁺, Pr³⁺, Nd³⁺, Dy³⁺, Er³⁺; M = Cu²⁺, Co²⁺, Ni²⁺; n = 4, 6). Suggestions on their structures were made. In the interval of 20–140°C, these complexes were shown to be high-resistance semiconductors.     

Enantioselective addition of diethyl malonate to ω-nitrostyrenes in the presence of cobalt and manganese complexes with N,N′-dibenzyl-(1S,2S)-cyclohexane-1,2-diamine

Enantioselective addition of diethyl malonate to nitrostyrene and para-chloronitrostyrene is catalyzed by cobalt and manganese complexes with N,N??-dibenzyl-(1S,2S)-cyclohexane-1,2-diamine generated in situ. Enantiomeric excess of the (R)-isomers in the reaction products is 66?C87%.     

Syntheses,crystal structures,and properties of optically active Lu(III) and Yb(III) complexes of N,N′-bis(2-hydroxybenzyl)-N,N′-bis(2-pyridylmethyl)-R-1,2-propanediamine with chloride or thiocyanate

The reaction of N,N′-bis(2-hydroxybenzyl)-N,N′-bis(2-pyridylmethyl)-R-1,2-propanediamine (R-bbppnH₂) with LnCl₃?6H₂O (Ln: Lu, Yb) stereoselectively gave an optically active complex, [LnCl(R-bbppn)], which crystallizes in the acentric space group of P2₁2₁2₁. The central lutetium(III) is coordinated by two oxygens from two phenolates, four nitrogens from two pyridines, and one bidentate propanediamine of R-bbppn^2?, one chloride to form a seven-coordinate distorted pentagonal bipyramidal geometry. Although two optical isomers, ΔΛΔ and ΛΔΛ, are possible for such a structure, the absolute configuration of the complex is stereoselectively unified to ΔΛΔ. The coordinated chloride of the complex is readily replaced by other ligands, and hence the reaction with thiocyanate results in formation of another seven-coordinate complex, [Ln(NCS)(R-bbppn)].     

Comeplexes of 1-(2′-hydroxybenzyl)-2-(2′-hydroxyphenyl)-benzimidazole with U(VI) and Ce(IV)

Some new U(VI) and Ce(IV) complexes of 1-(2′-hydroxybenzyl)-2-(2′-hydroxyphenyl)-benzimidazole have been prepared and characterized by spectrg magnetic and conductance studies. IR spectral data suggests that the ligand in all the complexes is monodenate through the tertiary nitrogen and that the phenolic oxygen is free from coordination. Conductivity measurements indicate that the nitrate and acetate complexes of U(VI) are non-electrolytes, whereas the nitrate complex of Ce(IV) is a 1:1 electrolyte.