以氯醌酸二价阴离子为桥联配体的Fe(Ⅲ)-Fe(Ⅲ)和Mn(Ⅱ)-Mn(Ⅱ)双核配合物的合成与磁性

基于铁和锰的双核配合物在生物氧化还原过程中的重要作用及在化学的氧化还原过程中可能做为催化剂的应用前景,本文合成了两个新的以氯醌酸二价阴离子为桥联配体的Fe(Ⅲ)双核和Mn(Ⅱ)双核配合物:[Fe_2(phen)_4(μ-CA)](ClO_4)_4·2H_2O(1)和[Mn_2(phen)_4(μ-CA)](ClO_4)_2·3H_2O(2)(phen=1,10菲咯啉;CA=氯醌酸二价阴离子)。经元素分析、IR、电子光谱及磁性等测定,对两配合物进行了表征。     

Triazine based Mn (II) and Mn (II)/Ln (III) complexes: Synthesis,characterization and catecholase activities

In the current work, two triazine‐based multidentate ligands (H₂L¹ and H₂L²) and their homo‐dinuclear Mn (II), mononuclear Ln (III) and hetero‐dinuclear Mn (II)/Ln (III) (Where Ln: Eu or La) complexes were synthesized and characterized by spectroscopic and analytical methods. Single crystals of a homo‐dinuclear Mn (II) complex {[Mn (HL¹)(CH₃OH)](ClO₄·CH₃OH}₂ ( 1 ) were obtained and the molecular structure was determined by X‐ray diffraction method. In the structure of the complex, each Mn (II) ion is seven‐coordinate and one of the phenolic oxygen bridges two Mn (II) centre forming a dimeric structure. The UV–Vis. and photoluminescence properties of synthesized ligands and their metal complexes were investigated in DMF solution and the compounds showed emission bands in the UV–Vis. region. The catecholase enzyme‐like activity of the complexes were studied for 3,5‐DTBC → 3,5‐DTBQ conversion in the presence of air oxygen. Homo‐dinuclear Mn (II) complexes ( 1 and 4 ) were found to efficiently catalyse 3,5‐DTBC → 3,5‐DTBQ conversion with the turnover numbers of 37.25 and 35.78 h^?1 (k_cat), respectively. Mononuclear Eu (III) and La (III) complexes did not show catecholase activity.     

铂电极上醋酸-醋酐溶液中Mn(III)/Mn(II)电对研究

平衡电极电势实验确定了25 ℃, 1.5 mol•L－1醋酸钾＋醋酸-醋酐(3:1体积比)溶液中Mn(III)/Mn(II)的条件电极电势为0.719 V（vs SCE）;采用电势扫描和旋转圆盘电极技术研究了醋酸-醋酐溶液中铂电极上Mn(III)/Mn(II)电对的阳极氧化动力学. 结果表明:Mn(II)阳极氧化成Mn(III)的电极反应控制步骤属电荷传递过程, 阳极传递系数β=0.347,交换电流密度i0=5.84×10－6 A•cm－2,阳极标准反应速率常数ka=1.35×10－8 m•s－1, Mn(II)和OAc－的反应级数均为一级.     

TG,DTA and electrical conductance properties of some Cu(II) AND Mn(II) bisazo- dianils complexes

The TG and DTA of a new series of Mn(II) and Cu(II) complexes with a number of newly prepared bisazo-dianil ligands were studied in the temperature range (20-700°C). The TG and DTG curves display to main steps, the first one within the temperature range (25-330°C) correspond to the elimination of water or and ethanol from the complexes. The second step within the range (350-625°C) is due to the decomposition of the complexes yielding the metal oxides as the final product. The rate constants of the dehydration and decomposition reactions were determined, from which some kinetic parameters were evaluated. The DTA curves show that the dehydration of the metal complexes is an endothermic reaction. In all cases the anhydrous metal complexes undergo exothermic decomposition reactions to give the metal oxide. The thermodynamic parameters (ΔE, ΔH, ΔS, ΔG) for the occurring processes are calculated. The electrical conductivities of the solid complexes were measured and the activation energy of the complex and its free ligand are also calculated. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of the pH on the complexation of Cu(II), Ni(II) and Fe(III) Ions by a vine leaf litter extract by fluorescence quenching

An extract of dead vine leaves (vitis viniferal) (VLE) was obtained by the extraction procedure for fulvic acids and its interaction (at a concentration of 25mg/L in 0.1 M KNO₃) with the Cu(II), Ni(II) and Fe(III) ions was studied in the pH range between 3 and 6. This interaction was monitored by synchronous molecular fluorescence, since bands due to the fluorescent ligands undergo quenching upon complex formation. After the chemometric isolation of the quenching profiles from the raw spectra by a self-modeling mixture analysis, SIMPLISMA, they were analyzed by two methods: (i) graphical procedures based on the Stern-Volmer model; and (ii) a non-linear least-squares procedure. For the Cu(II) and Ni(II) ions, the treatment by these two methods provided similar values both for the logarithm of the conditional stability constants (log Kc) and the percentage of fluorescent structures that do not participate in the complexation. The log Kc were (standard deviations in parenthesis): Cu(II) ion, 2.4 (3), 3.37(3), 4.4(1) and 4.92(9), respectively, for pH = 3, 4, 5 and 6; Ni(II)ion, 2.9(1), 3.3(2), and 4.09(3), respectively, for pH = 4, 5 and 6. For Fe(III) an interaction with VLE was observed, but no values for Kc could be obtained.     

Synthesis and structure of Mn(II) and Zn(II) complexes containing 1,10-phenanthroline unit

The Mn(II) and Zn(II) complexes of N,N′-diisopropyl-1,10-phenanthroline-2,9-dimethanamine have been synthesised, and the structure of the two complexes have been studied by X-ray crystallography.     

The Spectrophotometry Determination of Mn(III) in the Presence of Mn(IV)

Abstract

The spectra of complex of Mn(III) and Mn(IV) with pyrophosphoric acid are investigated. The molar absorption coefficient of the complex of Mn(III) with pyrophosphoric acid is 80.6/Mcm at 510nm which is close to that of Mn(IV), 110/Mcm, however, the molar absorption coefficient of the complex of Mn(HI) with pyrophosphoric acid is only 4.98/Mcm at 398nm which is much less than that of Mn(IV), 390/Mcm. Based on this absorbance difference between Mn(III) and Mn(IV) at wavelength 398nm and 510nm, a procedure of determination of Mn(III) in the presence of Mn(IV) has been developed.     

Cationic complexes of Eu(III) and Sr(II) with diphosphine dioxides in organic extracts

IR spectroscopy was used to study the structure and composition of Eu(III) and Sr(II) complexes formed by cation-exchange extraction of these metals from their aqueous nitrate solutions with dichlorethane solutions of mixtures of chlorinated cobalt(III) dicarbollide (CCD) as a superacid with diphenyldiphosphine dioxides containing a methyl (Me-DPDO), ethyl (Et-DPDO), or polyoxyethylene bridge between two phosphorus atoms of phosphine oxide groups. At molar ratios DPDO/CCD ≤ 1, [Eu(H₂O)_nL₄]³⁺ complexes are formed in organic phases, whereas with an excess of DPDO relative to CCD, Eu(NO₃)L ₄ ²⁺ complexes are formed, where L = Me-or Et-DPDO. Polyoxyethylenediphosphine dioxide forms anhydrous complexes of composition Eu:L = 1:1 and 1:2 with Eu(III) and outer-spheric complexes of composition Sr:L = 1:1 and 1:2 with Sr(II), where the organic ligand molecules envelop the hydrated Sr(H₂O) _n ²⁺ cation. The peculiarities of extraction of the complexes are explained based on data about their composition and structure.     

Mn (II) and Zn (II) complexes of a benzimidazole ligand having undecyl chains: Crystal structures,photophysical and thermal properties

A new tridentate benzimidazole ligand (L‐C¹¹) containing undecyl chains and its Mn (II) and Zn (II) complexes were synthesised and characterized by spectroscopic and analytical methods. Molecular structures of complexes [Mn(L‐C¹¹)Cl₂] and [Zn(L‐C¹¹)Cl₂] were evaluated by X‐ray diffraction studies. The X‐ray data showed metal ions in both complexes are five‐coordinate with distorted square pyramidal geometry around the metal centres. The undecyl chains in the structure of the complexes are aligned in an interdigitated manner (head to tail) forming a non‐polar domain. The aggregation properties of the ligand and its complexes were investigated by UV–Vis. absorption and emission spectroscopies in DMF‐water mixtures. The emission spectral data revealed that the compounds showed aggregation induced quenching (AIQ) in DMF‐water solutions. Moreover, thermal properties of the compounds were investigated by TG, DTG and DSC analysis.     

Oxidation Of Di-Peptides With Mn(III): Synthesis, Characterization And Mechanistic Study

Synthesis and characterization of the dipeptides(DP) namely Glycyl-Proline (Gly-Pro), Alanyl-Proline (Ala-Pro) and Valyl-Proline (Val-Pro), were made. Kinetics of oxidation of these DP by Mn(III) have been studied in the presence of sulfate ions in acidic medium at 26C. The reaction was followed spectrophotometrically at _max = 500 nm. A first order dependence of rate on both Mn(III) and DP was observed. The rate is independent of the concentration of reduction product, Mn(II) and hydrogen ions. Effects of varying dielectric constant of the medium and addition of anions such as sulfate, chloride and perchlorate were studied. Activation parameters have been evaluated using Arrhenius and Eyring plots. The oxidation products were isolated and characterized. A mechanism involving the reaction of DP with Mn(III) in the rate limiting step is suggested.     

A bulky oxime for the synthesis of Mn(III) clusters

The reaction between Mn(OAc)₂·4H₂O and Br-saoH₂ (=5-Br-salicylaldoxime) in EtOH in the presence of NMe₄OH led to the formation of the hexanuclear cluster [Mn₆O₂(Br-sao)₆(OAc)₂(H₂O)₂(EtOH)₂]·2.8H₂O·2.2EtOH (1). Switching from Mn(OAc)₂·4H₂O to Mn(ClO₄)₂·6H₂O, the same reaction upon addition of pivH (= trimethyl acetic acid) yielded [Mn₆O₂(Br-sao)₆(piv)₂(H₂O)₂(EtOH)₂]·6EtOH (2 6EtOH), and finally upon changing pivH to NaO₂CPh, we were able to isolate [Mn₆Na₂O₂(Br-sao)₆(O₂CPh)₄(H₂O)₂(EtOH)₄]·6EtOH (3 6EtOH). Clusters 1 and 2 6EtOH describe “typical” [Mn₆/oximate] complexes consisting of two {Mn₃} oxo-centered triangular units bridged by oximate groups, while in 3 6EtOH these triangular motifs are separated by two sodium cations. An investigation into the magnetic properties of all three clusters revealed the presence of dominant antiferromagnetic interactions, leading to ground states of S = 4 and 2 for 1 and 3, respectively. Finally, cluster 2 6EtOH functions as a single-molecule magnet with U_eff = 27.54 K.     

Kinetic Study of the Ce(III)‐, Mn(II)‐, or Ferroin‐Catalyzed Belousov‐Zhabotinsky Reaction with Allylmalonic Acid

In a stirred batch experiment and under aerobic conditions, ferroin (Fe(phen)₃²⁺) behaves differently from Ce(III) or Mn(II) ion as a catalyst for the Belousov‐Zhabotinsky (BZ) reaction with allylmalonic acid (AMA). The effects of bromate ion, AMA, metal‐ion catalyst, and sulfuric acid on the oscillating pattern were investigated. The kinetics of the reaction of AMA with Ce(IV), Mn(III), or Fe(phen)₃³⁺ ion was studied under aerobic or anaerobic conditions. The order of reactivity of metal ions toward reaction with AMA is Fe(phen)₃³⁺ > Mn(III) > Ce(IV) under aerobic conditions whereas it is Mn(III) > Ce(IV) > Fe(phen)₃³⁺ under anaerobic conditions. Under aerobic or anaerobic conditions, the order of reactivity of RCH(CO₂H)₂ (R = H (MA), Me (MeMA), Et (EtMA), allyl (AMA), n‐Bu (BuMA), Ph (PhMA), and Br (BrMA)) is PhMA > MA > BrMA > AMA > MeMA > EtMA > BuMA toward reaction with Ce(IV) ion and it is MA > PhMA > BrMA > MeMA > AMA > EtMA > BuMA toward reaction with Mn(III) ion. Under aerobic conditions, the order of reactivity of RCH(CO₂H)₂ toward reaction with Fe(phen)₃³⁺ ion is PhMA > BrMA > (MeMA, AMA) > (BuMA, EtMA) > MA. The experiment results are rationalized.     

Studies on Mn(II) and Mn(IV) Complexes of an Unsymmetrical Bidentate Donor,N(4-Chlorophenyl)-Pyridine-2-Aldimine (ClL): Crystal Structure of [Mn(ClL)2(NCS)2]

The synthesis, characterisation and X-ray structure of an Mn(II) compound, [Mn(ClL)₂(NCS)₂], is described. Oxidation of the compound by H₂O₂ leads to a mononuclear Mn(IV) compound [Mn(ClL)(ClL')(NCS)₂]ClO₄·2H₂O where one of the ClL ligands is oxidised to the corresponding amide ClL'. Oxidation of [Mn(ClL)₂(NCS)₂] by Ce(IV), however, leads to a binuclear Mn(IV) compound [Mn₂O(ClL')₃(ClL)(H₂O)₂](NCS)₂ClO₄·2MeCN. Electron transfer behaviour of the compounds was investigated by cyclic voltammetry and differential pulse voltammetry.     

Separation of Ga(III) from Cu(II), Ni(II) and Zn(II) in aqueous solution using synthetic polymeric resins

Poly (acrylamide-acrylic acid-dimethylaminoethylmethacrylate), p(AM-AA-DMAEM) and Poly(acrylamide-acrylic acid)-ethylenediaminetetracetic acid disodium, p(AM-AA)-EDTANa₂ were prepared by gamma radiation-induced template polymerization technique and used for the separation of Ga (III) from Cu (II), Ni (II), and Zn (II) in aqueous media. The effect of pH and contact time on the separation process was studied. The optimum pH value for the separation process is 3–3.5. The result shows that Ga (III) is first extracted while Cu (II), Ni (II) and Zn(II) are slightly extracted at this pH value. The recovery of metals using HCl, HNO₃ and H₂SO₄ has been studied. The resins may be regenerated using 2M HCl solutions.      

The excited states of bipyridyl and phenanthroline complexes of Fe(III), Ru(II) and Ru(III): A molecular orbital study

The semiempirical zero-differential-overlap molecular orbital model which was shown in earlier papers in this series to give a good account of the charge transfer and -* spectra of Fe(II) complexes with conjugated ligands such as 2,2-bipyridyl and 1,10-phenanthroline is extended to complexes having openshell ground states, such as those of Fe(III), and to complexes of Ru(II) and Ru(III). The results are used to assign the observed charge transfer and intra-ligand absorption bands to specific orbital transitions. Observed and calculated intensities are in good agreement: reasons are advanced for the much lower intensity of the charge transfer bands in Ru(III) compared to Ru(II) complexes.     

Pb(II) and Bi(III) complexes involving a Schiff base ligand: syntheses,structures, physical,and antioxidant properties

Two new complexes, {[PbL(NO₃)₂H₂O]H₂O}_n (1) and [BiL₂(NO₃)₂]NO₃ (2), based on (E)-3-chloro-6-[2-(pyrazin-2-ylmethylene)hydrazinyl]pyridazine (L) were synthesized and characterized by IR spectra, single-crystal X-ray diffraction, and elemental analyzes. X-ray single crystal diffraction experiments of 1 and 2 display that extensive hydrogen bonds and π…π stacking interactions construct the 1-D infinite chain {[PbL(NO₃)₂H₂O]H₂O}_n and [BiL₂(NO₃)₂]NO₃ into two 3-D supramolecular frameworks. Interestingly, pure phase PbO nano-particles were synthesized by thermolysis of 1 and characterized by scanning electron microscopy and X-ray powder diffraction analyzes. Furthermore, antioxidant activities of L, 1, and 2 were also studied.     

Synthesis,spectroscopic, and thermal analyses of trinuclear Mn(II), Co(II), Ni(II), and Zn(II) complexes with some sulfa derivatives

New bi- and trihomonuclear Mn(II), Co(II), Ni(II), and Zn(II) complexes with sulfa-guanidine Schiff bases have been synthesized for potential chemotherapeutic use. The complexes are characterized using elemental and thermal (TGA) analyses, mass spectra (MS), molar conductance, IR, ¹H-NMR, UV-Vis, and electron spin resonance (ESR) spectra as well as magnetic moment measurements. The low molar conductance values denote non-electrolytes. The thermal behavior of these chelates shows that the hydrated complexes lose water of hydration in the first step followed by loss of coordinated water followed immediately by decomposition of the anions and ligands in subsequent steps. IR and ¹H-NMR data reveal that ligands are coordinated to the metal ions by two or three bidentate centers via the enol form of the carbonyl C=O group, enolic sulfonamide S(O)OH, and the nitrogen of azomethine. The UV-Vis and ESR spectra as well as magnetic moment data reveal that formation of octahedral [Mn₂L¹(AcO)₂(H₂O)₆] (1), [Co₂(L¹)₂(H₂O)₈] (2), [Ni₂L¹(AcO)₂(H₂O)₆] (3), [Mn₃L²(AcO)₃(H₂O)₉] (5), [Co₃L²(AcO)₃(H₂O)₉] · 4H₂O (6), [Ni₃L²(AcO)₃(H₂O)₉] · 7H₂O (7), [Mn₃L³(AcO)₃(H₂O)₆] (9), [Co₂(HL³)₂(H₂O)₈] · 4H₂O (10), [Ni₃L³(AcO)₃(H₂O)₉] (11), [Mn₃L⁴(AcO)₃(H₂O)₉] · H₂O (13), [Co₂(HL⁴)₂(H₂O)₈] · 5H₂O (14), and [Ni₃L⁴(AcO)₃(H₂O)₉] (15) while [Zn₂L¹(AcO)₂(H₂O)₂] (4), [Zn₃L²(AcO)₃(H₂O)₃] · 2H₂O (8), [Zn₃L³(AcO)₃(H₂O)₃] · 3H₂O (12), and [Zn₃L⁴(AcO)₃(H₂O)₃] · 2H₂O (16) are tetrahedral. The electron spray ionization (ESI) MS of the complexes showed isotope ion peaks of [M]⁺ and fragments supporting the formulation.     

Hetero-binuclear chelates of Mn(II), Co(II) and Cu(II) o-cresolphthalein complexonates with other metal ions

Heterobinuclear metal chelates of Mn²⁺, Co²⁺ or Cu²⁺ and some transition metal ions with o-cresolphthalein complexone have been prepared and characterized. Elemental analyses are in agreement with proposed formulae. Thermal analyses (TGA and DTA) were used to determine the degradation products; some thermodynamic parameters were calculated. IR and UV-Vis spectra identified the mode of bonding between the metal ions and the ligand as well as its geometry. Magnetic moment determination and ESR spectra of the heterobinuclear complex revealed some antiferromagnetic interaction between the metal ions, which depends mainly on the two metal ions forming the chelate. Electrochemical studies of the complexes [DC-polarography and cyclic voltammetry (CV)] confirmed the existence and the nature of the metal ions in the chelate.