Synthesis,crystal structure,spectroscopy, and nuclease activity of copper(II) complexes containing N,N-bis(2-pyridylmethyl)amine ligand

[Cu(bpea)Cl]ClO₄ (1) and a new copper(II) complex [Cu(bpma)(Ph-COO)(H₂O)]ClO₄ (2) [bpea?=?N,N-bis(2-pyridylmethyl)ethylamine; bpma?=?N,N-bis(2-pyridylmethyl)methylamine] have been synthesized. Complex 2 was crystallized in monoclinic space group P2₁/c with unit cell parameters a ?=?16.460(6)?Å, b ?=?11.222(4)?Å, c?=?12.522(5)?Å, and β?=?97.985(6)°. Interactions of the complexes with calf thymus DNA (CT-DNA) have been investigated by UV absorption, fluorescence, and cyclic voltammetry; thus, modes of CT-DNA binding for the complexes have been proposed. Furthermore, DNA cleavage activities by the complexes were performed in the absence of any external agents. The influence of complex concentration or reaction time on the DNA cleavage was studied.     

Synthesis,characterization, and DNA-binding of Ln(III) complexes with 2-hydroxybenzylidene-2-phenylquinoline-4-carbonylhydrazone

2-Hydroxybenzylidene-2-phenylquinoline-4-carbonylhydrazone (H₂L) and five Ln(III) complexes, [Ln(H₂L)(NO₃)₂]NO₃ [Ln = La (1), Pr (2), Sm (3), Eu (4), and Tb (5)], have been synthesized and characterized by ¹H NMR, elemental analysis, conductivity measurements, mass spectra, IR spectra, and UV spectra. The interaction of these complexes with calf thymus DNA was investigated by UV absorption spectroscopy, fluorescence spectroscopy, circular dichroism spectroscopy and viscosity measurements. Results suggest that these complexes bind to DNA via groove binding.     

Synthesis and crystal structures of N,N'-bis(5-fluoro-2-hydroxybenzylidene)ethane-1,2-diamine and its dinuclear manganese(III) complex with antibacterial activities

A new dinuclear manganese complex, [Mn₂L₂(N₃)₂], was prepared by reaction of bis-Schiff base N,N'-bis(5-fluoro-2-hydroxybenzylidene)ethane-1,2-diamine (H₂L) with manganese acetate and sodium azide in methanol. Both the Schiff base and the complex were characterized by physico-chemical methods and single crystal X-ray determination. The Schiff base crystallized in the orthorhombic space group Pbca with unit cell dimensions a?=?7.3191(7)?Å, b?=?6.0948(6)?Å, c?=?35.382(3)?Å, V?=?1578.3(3)?ų, Z?=?4, R₁?=?0.0481, wR₂?=?0.1488. The manganese complex crystallized in the monoclinic space group P2₁/c with unit cell dimensions a?=?8.802(1)?Å, b?=?14.928(2)?Å, c?=?14.478(2)?Å, β?=?105.517(2)°, V?=?1833.0(4)?ų, Z?=?2, R₁?=?0.0768, wR₂?=?0.1640. There are crystallographic inversion centers in both the ligand and the complex. The ligand coordinates to Mn through all the phenolate oxygens and imino nitrogens. The two Mn in the complex are bridged by two phenolate oxygens with separation of 3.549(1)?Å. Each Mn is octahedral with four donors of the Schiff base ligand defining the equatorial plane, and with one azido nitrogen and one phenolate oxygen of an adjacent Schiff base ligand occupying the axial positions. The Schiff base and the complex were tested in vitro for their antibacterial activities.     

N,N′-Bis(2-hydroxybenzyl)ethylenediamine-N,N′-dipropionic acid. A new chelating ligand for iron(III)

A new potentially chelating ligandN,N′-bis(2-hydroxybenzyl)ethylenediamine-N,N′-dipropionic acid, (HBEP) has been prepared in high yield and its ionization constants have been determined by potentiometric and spectrophotometric methods. The stability constant for the Fe^III-HBEP chelate has been determined spectrophotometrically, and the ligational behaviour of HBEP with iron(III) compared with that of its homologue, HBED (N,N′-bis(2-hydroxybenzyl)ethylenediamine-N,N′-diacetic acid). IPCL Communication No. 169.     

A mononuclear nickel(II) complex and a dinuclear manganese(III) complex derived from N,N'-bis(5-methoxysalicylidene)-1,2-ethanediamine: Synthesis,crystal structures and catalytic epoxidation property

Synthesis and characterization of a mononuclear nickel(II) complex [NiL] · CH₃OH (I) and a dinuclear manganese(III) complex [Mn₂L₂(NCS)₂] (II) derived from the bis-Schiff base N,N'-bis(5-methoxysalicylidene)-1,2-ethanediamine (H₂L) are reported. The complexes were characterized by elemental analyses, IR spectra and molar conductivity. Single crystal X-ray structures of the complexes have been determined (CIF files CCDC nos. 1056778 (I) and 1056688 (II)). The Ni atom in I is in a square planar coordination, and the Mn atom in II is in an octahedral coordination. Catalytic property for epoxidation of styrene by the complexes using PhIO and NaOCl as oxidant has been studied. As a result, complex II is efficient for the styrene epoxidation.     

A spectral and electrochemical study of mononuclear manganese(III) complexes of a polybenzimidazolyl ligand

Summary A series of Mn^III complexes with stoichiometry [MnLX](Y)₂ have been synthesized utilizing an exogenous anionic ligand, X^- = OAc, SCN or N₃, and the hexadentate ligand N,N,N,N-tetrakis[2(benzimidazolyl) methyl-1,2-ethanediamine] and its N-octyl derivative. The vis. spectra of the compounds are in keeping with a pseudo-C _4v , symmetry for the Mn^III ion, implying that all the pendant arms of the hexadentate ligand do not bind to the Mn^III centre. Cyclic voltammetric studies reveal that the E _1/2 for the Mn^III/Mn^IV couple shifts to positive values with SCN^- as the anionic ligand, implying that this anion stabilizes the Mn^III oxidation state, whereas E _1/2 data for N₃ ^- reveals that the anion destabilizes the Mn^III state.     

Synthesis,crystal structures,and catalytic properties of phenoxo-bridged dinuclear manganese(III) complexes with bis-Schiff bases

Two structurally similar centrosymmetric phenoxo-bridged dinuclear manganese(III) complexes, [Mn₂(L¹)₂(N₃)₂] (1) and [Mn₂(L²)₂(NCS)₂] (2), were prepared from the tetradentate bis-Schiff base ligands, N,N’-bis(salicylidene)propane-1,2-diamine (H₂L¹) and N,N’-bis(salicylidene)ethane-1,2-diamine (H₂L²), respectively, in the presence of pseudohalides. The complexes have been characterized by FTIR, elemental analyses, and molar conductivity. Structures of the complexes have been confirmed by single-crystal X-ray determination. The bis-Schiff base ligands coordinate with Mn through their phenolate oxygen and imino nitrogen. Each Mn is an octahedral. The complexes showed that they exhibit high activity in catalytic olefin oxidation.     

Synthesis and spectral studies on mononuclear complexes of chromium(III) and manganese(II) with 12-membered tetradentate N2O2, N2S2 and N4 donor macrocyclic ligands

Complexes of Cr^III and Mn^II of general formula [Cr(L)X₂] X and [Mn(L)X₂] respectively were prepared from N₂O₂, N₂S₂ and N₄ donor macrocyclic ligands. The complexes have been characterized by elemental analysis, molar conductance measurements, spectral methods (i.r, mass, ¹H-n.m.r, electronic spectra and e.p.r.) and magnetic measurements. The macrocyclic ligands have three different donating atom cavities, one with two unsaturated nitrogens and the other two have saturated nitrogen, oxygen and sulphur atoms. The effect of different donor atoms on the spectra and ligand field parameters is discussed. All the complexes show magnetic moments corresponding to a high-spin configuration. On the basis of spectral studies a six coordinated octahedral geometry may be assigned to these complexes.     

The ternary metal mixed ligand complexes formed by benzimidazole and N, N-bis(2-hydroxyethyl) glycine

The stability constants of the ternary M(Bic)(Bzim)~ complexes, where M~(2 )=Cu~(2 ), Ni~(2 ) or Zn~(2 ), Bic~-=the anion of N, N-bis(2-hydroxyethyl) glycine and Bzim = benzimidazole, were determined by potentiometric pH titration in aqueous solution. One of them (M~(2 ) = Cu~(2 )) was also separately determined by spectrophotometry. The results show that these ternary complexes are stabler than expected on statistical grounds. The enhanced stability of the ternary M(Bic) (Bzim)~ complexes is attributed to the π_A-π_B cooperative effect between Bic~- and benzimidazole. Besides, compared with Cu(Bic) (Bzim)~ and Ni(Bic) (Bzim)~ , the ternary Zn(Bic)(Bzim)~ complex has relatively high stability. The crystal structure of [Cu(Bic)(Bzim)]ClO_4 was determined by single crystal X-ray diffraction techniques. The copper atom has a trigonal-bipyramidal geometry, the basal plane is formed by an oxygen atom of the carboxylato group and two hydroxyl oxygen atoms, the apical position is occupied by a nitrogen a     

Kinetics and mechanism of oxidation of N,N-bis(salicylaldehyde-1,2-diaminoethane) cobalt(II) by N-bromosuccinimide in aqueous acidic medium

The kinetics of oxidation of N,N-bis(salicylaldehyde-1,2-diaminoethane) cobalt(II) complex by N-bromosuccinimide (NBS) in aqueous acid and H₂O–MeOH solvent mixtures were studied spectrophotometrically over the 20–40 °C range, 0.1–0.5 mol dm^?3 ionic strength, 2.2–2.8 pH range and 0–40 wt% MeOH–H₂O solvent mixtures for a range of NBS and complex concentrations. The rate shows first-order dependence on both [NBS] and [complex] and decreases with pH over the range studied. The protonated form of N-bromosuccinimide was identified as the main reactive species. An inner-sphere mechanism involving free radicals is proposed.     

Redox chemistry of 1,2-dihydroxynaphthalene, 1,2-naphthosemiquinone and 1,2-naphthoquinone and their complexes with manganese(II) and manganese(III)

Cyclic voltammetry and controlled-potential electrolyses were carried out on solutions of 1,2-naphthoquinone (1,2-NQ), 1,2-dihydroxynaphthalene [1,2-Di(OH)-Cat] and their reduction and oxidation products in dimethyl sulfoxide. A study of the interaction of these species with MnII and MnIII has been undertaken. The complexes MnIII(Cat2–)33–, MnII(Cat2–)22– and MnII-(Cat2–), where Cat2– represents the dianion of 1,2-dihydroxynaphthalene, were obtained in solution and the species MnIISQ has been detected only on the surface of the electrode. An attempt to obtain the latter complex quantitatively caused intramolecular charge-transfer yielding the more stable MnIII-catechol complex. The MnIII–semiquinone complex is unstable and the ligand is easily oxidized. The charge-transfer reaction between MnIII(Cat2–)33– and MnII(Cat2–)22– is observed at –0.54/–0.52 V versus s.c.e. whereas the MnII complexes are reduced beyond the electrochemical window (at a potential more negative than –2.00 V versus s.c.e). On the other hand, all these species are destroyed when the coordinated ligand is oxidized. U.v.-vis. spectroscopy and magnetic susceptibility measurements were performed on the compounds in solution in order to characterize and to confirm the oxidation states of the metal ion in the species.     

Synthesis, structure, and properties of low-spin manganese(III)-poly(pyrazolyl)borate complexes

The manganese(III)-bis[poly(pyrazolyl)borate] complexes, Mn(pzb)2SbF6, where pzb- = tetrakis(pyrazolyl)borate (pzTp) (1), hydrotris(pyrazolyl)borate (Tp) (2), or hydrotris(3,5-dimethylpyrazolyl)borate (Tp*) (3), have been synthesized by oxidation of the corresponding Mn(pzb)2 compounds with NOSbF6. The Mn(III) complexes are low-spin in solution and the solid state (microeff = 2.9-3.8 microB). X-ray crystallography confirms their uncommon low-spin character. The close conformity of mean Mn-N distances of 1.974(4), 1.984(5), and 1.996(4) A in 1, 2, and 3, respectively, indicates absence of the characteristic Jahn-Teller distortion of a high-spin d4 center. N-Mn-N bite angles of slightly less than 90 degrees within the facially coordinated pzb- ligands produce a small trigonal distortion and effective D3d symmetry in 1 and 2. These angles increase to 90.0(4)degrees in 3, yielding an almost perfectly octahedral disposition of N donors in Mn(Tp*)2+. Examination of structural data from 23 metal-bis(pzb) complexes reveals systematic changes within the metal-(pyrazolyl)borate framework as the ligand is changed from pzTp to Tp to Tp*. These deformations consist of significant increases in M-N-N, N-B-N, and N-N-B angles and a minimal increase in Mn-N distance as a consequence of the steric demands of the 3-methyl groups. Less effective overlap of pyrazole lone pairs with metal atom orbitals resulting from the M-N-N angular displacement is suggested to contribute to the lower ligand field strength of Tp* complexes. Mn(pzb)2+ complexes undergo electrochemical reduction and oxidation in CH3CN. The electrochemical rate constant (ks,h) for reduction of t2g4 Mn(pzb)2+ to t2g3eg2 Mn(pzb)2 (a coupled electron-transfer and spin-crossover reaction) is 1-2 orders of magnitude smaller than that for oxidation of t2g4 Mn(pzb)2+ to t2g3 Mn(pzb)22+. ks,h values decrease as Tp* > pzTp > Tp for the Mn(pzb)2+/0 electrode reactions, which contrasts with the behavior of the comparable Fe(pzb)2+/0 and Co(pzb)2+/0 couples.     

Thermal behavior of Mannich base N,N′-tetra(4-antipyrylmethyl)-1,2-diaminoethane (TAMEN) and its complexes

The thermal decomposition in air and in nitrogen atmosphere of binuclear complex compounds of Cu(II) and Co(II) containing the Mannich base N,N′-tetra(4-antipyrylmethyl)-1,2 diaminoethane (TAMEN) as a ligand, Cu₂(TAMEN)Cl₄ and Co₂(TAMEN)Cl₄, were investigated. X-ray powder diffractometry, infrared spectroscopy and simultaneous thermogravimetry-differential thermal analysis (TG-DTA), have been used to characterize and to study the thermal behavior of these compounds. The results provided information concerning the stoichiometry, crystallinity, thermal stability and decomposition mechanism of the compounds.     

N,N-二(2-羟乙基)-2-氨基乙磺酸钠的合成研究

采用二乙醇胺与2-氯乙基磺酸钠反应合成N,N-二(2-羟乙基)-2-氨基乙磺酸钠(BES钠盐),由核磁氢谱(1H NMR)和碳谱(13C NMR)、红外光谱(FT-IR)、X射线衍射(XRD)等仪器表征了合成产物的结构和特性.根据反应体系pH值的变化及核磁谱图,确定了BES钠盐的最佳合成工艺:反应物料比为1:1:1,反...     

Synthesis,structure, electrochemical properties,and antioxidant activities of copper(II) and zinc(II) complexes with N,N-bis(N-ethyl-2-ylmethylbenzimidazol)allylamine ligand

N,N-bis(N-methyl-2-ylmethylbenzimidazole)aniline (EtAIDB) and its transition metal complexes, [Cu(EtAIDB)Br₂]·EtOH {dibromo[N,N-bis(N-methyl-2-ylmethylbenzimidazole)aniline] copper(II) ethanol} (1) and [Zn(EtAIDB)Br₂] {dibromo[N,N-bis(N-methyl-2-ylmethylbenzimidazole)aniline] zinc(II)} (2), have been synthesized and characterized by elemental analysis, molar conductivity, UV–visible, and IR spectroscopy. The X-ray crystallographic studies of 1 and 2 have shown two different arrangements: 1 is distorted square-based pyramidal, while 2 can be treated as distorted tetrahedral. The cyclic voltammogram of 1 represents quasi-reversible Cu²⁺/Cu⁺ pairs. In vitro antioxidant tests showed that 1 had significant antioxidant activity against superoxide and hydroxy radicals.     

Iron(III) complexes of a tetradentate tripodal ligand N,N′,N″-tris (2-benzimidazolyl-methyl)amine

Summary Fe^III complexes of a tetradentate ligand with pendant benzimidazolyl groups have been synthesized and characterized. Room temperature Mössbauer spectra depict a quadruple split doublet in the case of NO _inf3 ^p– as co-ligand, while a nearly symmetrical one line spectrum is obtained for complexes with Cl^–as co-ligand. The isomer shift values are towards the lower end of the range found for other high spin Fe^III complexes. ¹H-n.m.r. spectra of the complexes reveal relatively broad linewidths with large isotropic shifts. Paramagnetically shifted resonances are observed in the range of –10.0–+70.0 p.p.m.Author to whom all correspondence should be directed.