Synthesis and characterization of manganese(IV) and ruthenium(III) complexes derived from bis (2-hydroxy-1-naphthaldehyde)oxaloyldihydrazone

Bis(2-hydroxy-1-naphthaldehyde)oxaloyldihydrazone(naohH₄) interacts with manganese(II) acetate in methanol followed by addition of KOH giving [Mn^IV(naoh)(H₂O)₂]. Activated ruthenium(III) chloride reacts with naohH₄ in methanol yielding [Ru^III(naohH₄)Cl(H₂O)Cl₂]. The replacement of aquo by heterocyclic nitrogen donor in these complexes has been observed when the reaction is carried out in presence of heterocyclic nitrogen donors such as pyridine(py), 3-picoline(3-pic) or 4-picoline(4-pic). The molar conductance values in DMF for these complexes suggest non-electrolytic nature. Magnetic moment values suggest +4 oxidation state for manganese in its complexes, however, ruthenium(III) complexes are paramagnetic with one unpaired electron. Electronic spectral studies suggest six coordinate metal ions. IR spectra reveal that naohH₄ coordinates in enol-form and keto-form to manganese and ruthenium, respectively. ESR and cyclic voltammetric studies of the complexes have also been reported.     

Studies in negative ion mass spectrometry. X—Electron capture by a series of tris(hexafluoroacetylacetonato) metal chelates

Results of electron capture and negative ion mass spectrometric studies are reported for a series of tris-chelates of the type Metal. L₃, where L refers to the ligand or enolate ion of the β-diketone 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (hexafluoracetylacetone), and the metals are: Sc(III), Ti(III), V(III), Cr(III), Mn(III), Fe(III), Co(III), A1(III), Ga(III), In(III). The negative ion mass spectra were all relatively simple; the most abundant ions being the molecular and ligand ions for all the metals studied. Reaction schemes have been established to account for the appearance of all significant fragment ions, many of which have been formed as a result of fluorine atom transfer processes. For the transition metal complexes, evidence for elimination of neutral divalent metal fluorides comes from the ion decomposition reactions [Metal.L.F₂]^?→[L]^?, and for the Group III metal complexes, [Metal.L₃]^?→[Metal.L₂]^? as well as [Metal.L₂]^?→[L]^? processes indicate that the metals have been reduced as a consequence of the initial electron capture and subsequent fragmentations of metal-containing ions. The influence of the metal atom and its 3d-electron configuration has been shown not to affect significantly the electron capture processes. However, the relative instabilities of molecular anions of the transition metal tris-complexes show an approximately linear dependence on the increasing 3d-electron populations of the metal ions from Ti(III) to Co(III).     

Synthesis and structural characterization of manganese(III,IV) and ruthenium(III) complexes derived from 2-hydroxy-1-naphthaldehydebenzoylhydrazone

Reaction of 2-hydroxy-1-naphthaldehydebenzoylhydrazone(napbhH₂) with manganese(II) acetate tetrahydrate and manganese(III) acetate dihydrate in methanol followed by addition of methanolic KOH in molar ratio (2 : 1 : 10) results in [Mn(IV)(napbh)₂] and [Mn(III)(napbh)(OH)(H₂O)], respectively. Activated ruthenium(III) chloride reacts with napbhH₂ in methanolic medium yielding [Ru(III)(napbhH)Cl(H₂O)]Cl. Replacement of aquo ligand by heterocyclic nitrogen donor in this complex has been observed when the reaction is carried out in presence of pyridine(py), 3-picoline(3-pic) or 4-picoline(4-pic). The molar conductance values in DMF (N,N-dimethyl formamide) of these complexes suggest non-electrolytic and 1 : 1 electrolytic nature for manganese and ruthenium complexes, respectively. Magnetic moment values of manganese complexes suggest Mn(III) and Mn(IV), however, ruthenium complexes are paramagnetic with one unpaired electron suggesting Ru(III). Electronic spectral studies suggest six coordinate metal ions in these complexes. IR spectra reveal that napbhH₂ coordinates in enol-form and keto-form to manganese and ruthenium metal ions in its complexes, respectively. ESR studies of the complexes are also reported.     

Synthesis and properties of transition and lanthanide complexes with benzyl monohydrazone-3-hydrazine- 4-benzyl-6-phenyl pyridazine ligand (BHP)

Synthesis and characterization of benzyl-monohydrazone-3-hydrazino-4-benzyl-6-phenyl pyridazine (BHP) and its complexes with copper(II), nickel(II), cobalt(II), zinc(II), manganese(II), cadmium(II), thorium(IV), dioxyuranium(VI), samarium(III) and erbium(III) are presented. The protonation equilibrium of BHP ion and complex formation equilibrium with the metal ions have been studied by potentiometry in 75% (v/v) dioxane-water and 0.10M KNO₃ at different temperatures (10, 20, 30 and 40°C). A series of mononuclear complexes [ML _n ]^{(1? z )+} (L^? =?BHP and n =?1 ??z) were found in solution and their formation constants, enthalpies and entropies were determined.

The solid metal complexes and corresponding thermal products were elucidated by elemental analysis, conductance, IR and electronic spectra, magnetic moments, ¹H NMR and TG-DSC measurements as well as by mass spectroscopy. The use of BHP as analytical reagents for the determination of copper(II), nickel(II) and cobalt(II) as well as extracting agents for these metal ions are discussed.     

Spectro-thermal characterization of chromium(III) and manganese(II) complexes with carboxyamide

Complexes of Cr(III) and Mn(II) with N′,N″-bis(3-carboxy-1-oxopropanyl) 2-amino-N-arylbenzamidine (H₂L¹) and N′,N″-bis(3-carboxy-1-oxophenelenyl) 2-amino-N-arylbenzamidine (H₂L²) have been synthesized and characterized by various physico-chemical techniques. The vibrational spectral data are in agreement with coordination of amide and carboxylate oxygen of the ligands with the metal ions. The electronic spectra indicate octahedral geometry around the metal ions, supported by magnetic susceptibility measurements. The thermal behavior of chromium(III) complexes shows that uncoordinated nitrate is removed in the first step, followed by two water molecules and then decomposition of the ligand; manganese(II) complexes show two waters removed in the first step, followed by removal of the ligand in subsequent steps. Kinetic and thermodynamic parameters were computed from the thermal data using Coats and Redfern method, which confirm first order kinetics. The thermal stability of metal complexes has been compared. X-ray powder diffraction determines the cell parameters of the complexes.     

Novel repaglinide complexes with manganese(II), iron(III), copper(II) and zinc(II): Spectroscopic,DFT characterization and electrochemical behaviour

Novel transition metal complexes with the repaglinide ligand [2-ethoxy-4-[N-[1-(2piperidinophenyl)-3-methyl-1-1butyl] aminocarbonylmethyl]benzoic acid] (HL) are prepared from chloride salts of manganese(II), iron(III), copper(II), and zinc(II) ions in water-alcoholic media. The mononuclear and non-electrolyte [M(L)₂(H₂O)₂]?nH₂O (M = Mn²⁺, n = 2, M = Cu²⁺, n = 5 and M = Zn²⁺, n = 1) and [M(L)₂(H₂O)(OH)]?H₂O (M = Fe³⁺) complexes are obtained with the metal:ligand ratio of 1:2 and the L-deprotonated form of repaglinide. They are characterized using the elemental and molar conductance. The infrared, ¹H and ¹³C NMR spectra show the coordination mode of the metal ions to the repaglinide ligand. Magnetic susceptibility measurements and electronic spectra confirm the octahedral geometry around the metal center. The experimental values of FT-IR, ¹H, NMR, and electronic spectra are compared with theoretical data obtained by the density functional theory (DFT) using the B3LYP method with the LANL2DZ basis set. Analytical and spectral results suggest that the HL ligand is coordinated to the metal ions via two oxygen atoms of the ethoxy and carboxyl groups. The structural parameters of the optimized geometries of the ligand and the studied complexes are evaluated by theoretical calculations. The order of complexation energies for the obtained structures is as follows:

$$Fe(III) complex < Cu(II) complex < Zn(II) complex < Mn(II) complex.$$

The redox behavior of repaglinide and metal complexes are studied by cyclic voltammetry revealing irreversible redox processes. The presence of repaglinide in the complexes shifts the reduction potentials of the metal ions towards more negative values.

     

Preparation and surface photoelectric properties of Fe(II/III) complexes

Four Fe(II/III) supramolecules, {[Fe(Hpdc)₂(H₂O)₂]·2H₂O} (1), [Fe(HImbc)₂(H₂O)₂] (2), [Fe(phen)₂(CN)₂]·CH₃CH₂OH·2H₂O (3), K[Fe(tp)₂]·SO₄ (4) (H₂pdc = 2,5-Pyridinedicarboxylic acid, H₂Imbc = 4,5-Imidazoledicarboxylic acid, phen = 1,10-phenanthroline, tp⁻ = poly(pyrazolyl)borate), were synthesized by hydrothermal and room temperature stirring methods. They were characterized by single crystal X-ray diffraction, surface photovoltage spectroscopy (SPS), field-induced surface photovoltage spectroscopy (FISPS), electron paramagnetic resonance (EPR), UV–Vis absorption spectra (UV–Vis), infrared spectra (IR) and element analysis. The structural analyses indicate that complex (1) is a supramolecule with 2D structure connected by hydrogen bonds. Complex (2) is a supramolecule with hydrogen-bonded 3D structure. Complexes (3) and (4) are both 1D supramolecules connected by hydrogen bonds. The electronic state of central metal Fe(II) ions in complexes (1) and (2) is d⁶ with FeN₂O₄ coordination mode, lying in weaker distorted octahedral field. The electronic state of Fe(II) ion in complex (3) is d⁶ with Fe(CN)₂N₄ mode in the strong distorted octahedral field. The electronic state of Fe(III) ion in complex (4) is d⁵ with FeN₆ mode, lying in the strong octahedral field. The micro-environment of Fe(II/III) ions in the four complexes is further investigated by EPR. The SPS of four complexes all exhibit photovoltage responses in the range of 300–700 nm. This indicates that they all possess certain photoelectric conversion capability. The effects of component, structure, type of ligands of the complexes, valence state and coordination micro-environment of the central metal ions on the SPS were discussed. Furthermore, the SPS and UV–Vis absorption spectra were interrelated.     

Syntheses and structural analyses of nine-coordinate protonated (Py)2[GdIII(HNta)(Nta)(H2O)] · 5H2O and eight-coordinate (NH4)3[HoIII(Nta)2] complexes

The syntheses and structural determination of Gd(III) and Ho(III) complexes with nitrilotriacetic acids (Nta) were reported in this paper. Their structures and compositions were determined and characterized by single-crystal X-ray structure analyses, elemental analyses, and IR spectra. The first protonated Nta complex was found. Structural analyses indicate that the structure greatly changes, while an alternative Nta ligand was protonated in the ((Py)₂[Gd^III(HNta)(Nta)(H₂O)] · 5H₂O complex and the(NH₄)₃[Ho^III(Nta)₂] complex crystallized as a centrosymmetric structure. By contrast, it is further confirmed that the coordination number and coordinate structure of all trivalent rare-earth metal complexes with aminopolycarboxylic acids mainly depend on the ionic radii and electronic configuration of the central metal ions and their countercations.     

Conversion of low spin states in a monochelate complex of Fe(III) with an asymmetric tridentate azomethine ligand

An iron(III)-containing complex with the asymmetric tridentate azomethine ligand 4,4′-dodecyloxybenzoyloxybenzoyl-4-salicylidene-N′-ethyl-N-ethylenediamine with a PF ₆ ^? counterion is obtained. The presence of the complexing ion is confirmed by far IR Fourier spectra. The structure of the compounds is determined by matrix-assisted laser desorption/ionization with a time-of-flight mass analyzer (MALDI-ToF). The results of mass spectrometric studies are consistent with the elemental analysis data. It is found that the complexation of iron salt with an asymmetric tridentate ligand results in the formation of compounds of the composition 1:1 with octahedral packing of a metal ion in the complex. The electrochemical behavior of the compound in organic solvents is examined. The EPR study shows that iron(III) ions are in both low spin (LS) and high spin (HS) states in the complex. The LS and HS iron(III) centers are coupled into dimers in which a water molecule and the PF ₆ ^? counterion act as bridges. It is also found that for LS complexes in the lowtemperature phase (4.2–300 K), the (d _xz ,d _yz )⁴(d _xy )¹ electronic state is the ground state. It is revealed that the conversion of the sample into a high-temperature liquid crystalline (387–405 K) phase is accompanied by the conversion of the LS states of the Fe(III) ion: (d _xz ,d _yz )⁴(d _xy )¹ ? (d _xy )²(d _xz ,d _yz )³. The conversion of LS states is temperature reversible and is driven by the temperature. X-ray crystallographic data confirm that the compound obtained consists of dimer formed by a hydrogen (O-H...F) bond.     

Mononuclear and binuclear manganese(II) complexes with tridentate bis-benzimidazolyl ligands

Summary Manganese(II) complexes of bis(2-benzimidazolylmethyl) ether (DGB), bis(2-benzimidazolylmethyl) sulphide (TGB) and the n-butyl derivative of DGB (BDGB) were prepared and characterised. The solution e.p.r. spectrum of [Mn(TGB)Cl₂] in DMF at 143 K is commensurate with an axially distorted monomeric manganese(II) complex, room temperature magnetic moment (6.04 B.M.) per manganese(II) atom being in the range found for other d⁵ monomeric manganese(II) complexes. The solution e.p.r. spectrum of [Mn(BDGB)Cl₂]-2H₂O in DMF at 143 K indicates the presence of two equivalent manganese(II) ions coupled by an exchange interaction, fostered by bridging chlorides. Evidence for this is provided by a nearly isotropic 11 line hyperfine structure of ⁵⁵Mn, with a coupling constant 45 ± 5G. Contact-shifted ¹H n.m.r. data also supports an exchange coupled dimeric manganese complex. The room temperature magnetic moment, 5.64 B.M., per manganese(II) indicates quenching of the magnetic moment below that of monomeric manganese(II) ion. The [Mn(DGB)Cl₂]·H₂O complex exhibits a magnetic moment of 6.02 B.M. per manganese, indicating a monomeric manganese complex. E.p.r. data of the complex diluted in an analogous Zn-DGB complex (1∶20) correlates well for D = 0.22cm⁻¹ and λ ∼- 0.267. The [Mn(DGB)-(C1O₄)₂] and [Mn(BDGB)(ClO₄)₂] complexes, diluted in analogous Zn-DGB and Zn-BDGB complexes (1∶20), show a strong single e.p.r. line at g _eff ∼- 2. The complexes have low magnetic moments; 4.44 B.M./Mn and 4.39 B.M./Mn, at room temperature.     

Heteronuclear complexes of oxorhenium(V) with Fe(III), Co(II), Ni(II), Cu(II), Cd(II) and UO2(VI) and their biological activities

Heteronuclear complexes containing oxorhenium(V), with Fe(III), Co(II), Ni(II), Cu(II), Cd(II) and UO₂(VI) ions were prepared by the reaction of the complex ligands [ReO(HL¹)(PPh₃)(OH₂)Cl]Cl (a) and/or [ReO(H₂L²)(PPh₃)(OH₂)Cl]Cl (b), where H₂L¹?=?1-(2-hydroxyphenyl)butane-1,3-dione-3-(5,6-diphenyl-1,2,4-triazine-3-ylhydrazone) and H₃L²?=?1-(2-hydroxyphenyl)butane-1,3-dione-3-(1H-benzimidazol-2-ylhydrazone), with transition and actinide salts. Heterodinuclear complexes of ReO(V) with Fe(III), Co(II), Ni(II), Cu(II) and Cd(II) were obtained using a 1?:?1 mole ratio of the complex ligand and the metal salt. Heterotrinuclear complexes were obtained containing ReO(V) with UO₂(VI) and Cu(II) using 2?:?1 mole ratios of the complex ligand and the metal salts. The complex ligands a and b coordinate with the heterometal ion via a nitrogen of the heterocyclic ring and the nitrogen atom of the C=N⁷ group. All transition metal cations in the heteronuclear complexes have octahedral configurations, while UO₂(VI)?complexes have distorted dodecahedral geometry. The structures of the complexes were elucidated by IR, ESR, electronic and ¹H NMR spectra, magnetic moments, conductance and TG-DSC measurements. The antifungal activities of the complex ligands and their heteronuclear complexes towards Alternaria alternata and Aspergillus niger showed comparable behavior with some well-known antibiotics.     

Radical CpNi(dithiolene) and CpNi(diselenolene) complexes: Synthetic routes and molecular properties

The formally Ni(III) d⁷ radical organometallic complexes formulated as [CpNi(dithiolene)] can be prepared by different routes involving different CpNi sources such as the Ni^(I) [CpNi(CO)]₂, the Ni^(II) [Cp₂Ni] or [CpNi(cod)]⁺ or the Ni^(III) [Cp₂Ni]⁺ complexes. As dithiolene precursors, the naked dithiolate, the mono- as well as bis-(dithiolene) metal complexes were investigated. The highest yields are generally associated with an appropriate redox match, that is a CpNi^(II) precursor with a formally Ni^(IV) [Ni(dithiolene)₂]⁰ complex, or a CpNi^(III) precursor with a formally Ni^(III) [Ni(dithiolene)₂]^? complex. The structural, electrochemical and spectroscopic (UV–vis–NIR, EPR) properties of more than twenty complexes are described and compared, with the help of DFT calculations. They all exhibit a small optical gap with a low-energy absorption band in the Near Infra-Red region, between 700 and 1000 nm. The smaller electrochemical and optical gap found in the [CpNi(dmit)] and [CpNi(dddt)] complexes is correlated with an extensive delocalisation of the spin density in these complexes, while the other members of the series are characterized with a larger and sizeable spin density on the cyclopentadienyl ring.     

A series of new pyridine carboxamide complexes and self-assemblies with Tb(III), Eu(III), Zn(II), Cu(II) ions and their luminescent and magnetic properties

In this study, we present eight new complexes and self-assemblies of Tb(III), Eu(III), Zn(II) and Cu(II) ions with novel pyridine carboxamides, L1 [methyl 4-methyl-3-(pyridine-4-carbonylamino)benzoate] and L2 [methyl 2-methyl-3-(pyridine-4-carbonylamino)benzoate], as heterocyclic ligands. Two luminescent and spatially organized coordination compounds were obtained with the use of the solvothermal synthesis method, (1) [Tb₃(L1)₄(BTC)₃(H₂O)₃] (where BTC is benzene-1,3,5-tricarboxylic acid) and (5) [Eu(L2a)₃(H₂O)₃](H₂O)₄. As a result of one pot reaction synthesis under reflux the d-electron metal ions and self-organization of ligands gave complexes (2) [Zn(L1)₂Cl₂], (3) [Cu(L1)₂(SCN)₂(H₂O)], (4) [Cu(L1)₂Cl₂], hybrid salt (6) [(CuCl₄)^2-(L2b)₂²⁺](H₂O), (7) [Cu(L2)₂Cl₂] and 1D-chain coordination polymer (8) [Cu(L2)₂(SCN)₂]. Identification of the obtained compounds was performed on the basis of the excitation, emission, ¹H NMR, FT-IR spectra, luminescence lifetimes, SEM images, PXRD, single-crystal X-ray diffraction, MS, TGA and elemental analysis. Selected compounds were also analyzed in terms of their potential magnetic properties.     

Cerium(IV)‐Driven Water Oxidation Catalyzed by a Manganese(V)–Nitrido Complex

The study of manganese complexes as water‐oxidation catalysts (WOCs) is of great interest because they can serve as models for the oxygen‐evolving complex of photosystem II. In most of the reported Mn‐based WOCs, manganese exists in the oxidation states III or IV, and the catalysts generally give low turnovers, especially with one‐electron oxidants such as Ce^IV. Now, a different class of Mn‐based catalysts, namely manganese(V)–nitrido complexes, were explored. The complex [Mn^V(N)(CN)₄]²⁻ turned out to be an active homogeneous WOC using (NH₄)₂[Ce(NO₃)₆] as the terminal oxidant, with a turnover number of higher than 180 and a maximum turnover frequency of 6 min⁻¹. The study suggests that active WOCs may be constructed based on the Mn^V(N) platform.     

Oxovanadium(IV), manganese(II) and manganese(III) carbodithioates exhibiting abnormal magnetic behaviour

Summary New carbodithioate complexes of the oxovanadium(IV), manganese(II) and manganese(III) ions have been prepared and studied by i.r. and electronic spectral and variable temperature magnetic susceptibility (77K to room temperature) measurements. The carbodithioate ligands, 4-methylpiperazine-1-carbodithioate (4-MPipzcdt) and 4-phenylpiperazine-1-carbodithioate (4-PPipzcdt), were derived from heterocyclic secondary amines. The VO(4-MPipzcdt)₂ and VO(4-PPipzcdt)₂ complexes possess C _4v symmetry; Mn(4-PPipzcdt)₂ is tetrahedral and Mn(4-PPipzcdt)₃ is octahedral. All exhibit abnormal room temperature magnetic moments and the variable temperature magnetic moments suggest antiferromagnetism for the oxovanadium(IV) and the manganese(II) complexes and the occurrence of low spin (³ T _1g ) high spin (⁵ E _g ) equilibrium in addition to antiferromagnetic interactions in the manganese(III) complex. The spin-spin exchange parameter (-2J) value for the VO(4-MPipzcdt)₂ complex has been calculated using variable temperature magnetic susceptibility data.     

Solvothermal Synthesis and Crystal Structures of Two Manganese Complexes [Mn(II)(acac−)2(4,4′‐bipy)]n (bipy=4,4′‐bipyridine) and [Mn(III)(acac−)3]·4CO(NH2)2

Two special manganese complexes [Mn(II)(acac^?)₂(4,4′‐bipy)]_n (bipy=4,4′‐bipyridine) (complex 1 ) and [Mn(III)(acac^?)₃]·4CO(NH₂)₂ (acacH=acetylacetone) (complex 2 ) were synthesized in the same strategy by solvothermal method. Single crystal X‐ray diffraction revealed the complex 1 consists of one‐dimensional infinite coordination chain, with the manganese centers bridged by 4,4′‐bipy. And free carbamides of complex 2 connect with each other through the hydrogen bonds to form a 14‐membered carbamide ring and a zig‐zag plane. Both enantiomers of Mn(III)(acac^?)₃ exist in the structure, forming a racemate. Furthermore, these enantiomers and those zig‐zag planes are linked with hydrogen bonds to form an unique spatial network.     

A Novel Architecture of a Heptadentate Macroacyclic 2,6-Bis [(3-methoxy salicylidene) Hydrazino carbonyl] Pyridine Towards Lanthanides: A Synthetic and Structural Studies of Dinuclear Lanthanide (III) Complexes

Reaction of Ln(NO₃)₃ with 2,6-bis[(3-methoxysalicylidene)hydrazino carbonyl]pyridine (BMSPD) afforded binuclear complexes of the type [Ln₂(BMSPD)(NO₃)₂(H₂O)₅]·3H₂O in case of La(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III) and Dy(III), and [Ln₂(BMSPD)(NO₃)₂(H₂O)₅] in case of Y(III). The mode of coordination of ligand and the conformational changes on complexation with lanthanides was studied based on elemental analysis, magnetic studies, TG/DTA, IR, ¹H-NMR, Electronic, EPR and Fluorescence spectral studies. The ligand coordinates to one metal centre through enolized deprotonated carbonyls and pyridine nitrogen whereas doubly deprotonated phenolate oxygens and two hydrazonic nitrogens ligate to another lanthanide centre. Both the metal ions are in eight-coordination environments. The ligand and complexes were further tested for antifungal and antibacterial activities.     

Studies on Cobalt(III) Metallosurfactants. Kinetics and Mechanism of Reduction of Cobalt(III) by Iron(II) in Aqueous Acid Medium

The kinetics and mechanism of reduction of the surfactant complex ions, cis-chloro/bromo(dodecylamine)(triethylenetetramine)cobalt(III) by iron(II) in aqueous solution were studied at 303, 308 and 313 K by spectrophotometry under pseudo-first-order conditions using an excess of the reductant. The second-order rate constant increases with cobalt(III) concentration and the presence of aggregation of the complex itself alters the reaction rate. The reductions are acid-independent in the range [H⁺] = 0.05–0.25 mol dm⁻³. Variation of ionic strength (μ) influences the reaction rate. Activation and thermodynamic parameters have been computed. It is suggested that the reaction of Fe²⁺(aq) with the cobalt(III) complex proceeds by an inner-sphere mechanism. The critical micelle concentration (CMC) values of these surfactant metal complexes in aqueous solution were obtained from conductance measurements. Specific conductivity data (at 303, 308 and 313 K) served for the evaluation of the temperature-dependent CMC and the standard Gibbs energy of micellization (ΔG_m⁰).     

Synthesis and spectral studies of macrocyclic Pb(II), Zn(II), Cd(II) and La(III) complexes by template reaction of 1,2-bis(2-formylphenyl)ethane with metal nitrate and various diamine

Eight new macrocyclic complexes were synthesized by template reaction of 1,4-bis(3-aminopropoxy)butane or (±)-trans-1,2-diaminocyclohexane with metal nitrate and 1,2-bis(2-formylphenyl)ethane and their structures were proposed on the basis of elemental analysis, FT-IR, UV-Vis, molar conductivity measurements, ¹H NMR and mass spectra. The metals to ligand molar ratios of the complexes were found to be 1: 1. The complexes are 1: 2 electrolytes for Cd(II), Pb(II) and Zn(II) complexes and 1: 3 electrolytes for La(III) as shown by their molar conductivities (Λ_m) in DMSO at 10⁻³ mol L⁻¹. Due to the existence of free ions in these complexes, such complexes are electrically conductive. The configurations of Cd(II) and Zn(II) complexes were proposed to probably tetrahedral, La(III) complexes are octahedral and Pb(II) complexes are octahedral geometry in the L¹ complex and tetrahedral geometry in the L² complex.     

Kinetics of Reduction of Some Surfactant-Cobalt(III) Complexes by Iron(II)

The electron transfer kinetics of the reaction between the surfactant-cobalt(III) complex ions, cis-[Co(en)₂(C₁₂H₂₅NH₂)₂]³⁺, cis-α-[Co(trien)(C₁₂H₂₅NH₂)₂]³⁺(en:ethylenediamine, trien:triethylenetetramine, C₁₂H₂₅NH₂ : dodecylamine) by iron(II) in aqueous solution was studied at 298, 303, 308 K by spectrophotometry method under pseudo-first-order conditions using an excess of the reductant in self-micelles formed by the oxidant, cobalt(III) complex molecules, themselves. The rate constant of the electron transfer reaction depends on the initial concentration of the surfactant cobalt(III) complexes. ΔS^# also varies with initial concentration of the surfactant cobalt(III) complexes. By assuming outer-sphere mechanism, the results have been explained based on the presence of aggregated structures containing cobalt(III) complexes at the surface of the self-micelles formed by the surfactant cobalt(III) complexes in the reaction medium. The rate constant of each complex increases with initial concentration of one of the reactants surfactant-cobalt(III) complex, which shows that self micelles formed by surfactant-cobalt(III) complex itself has much influence on these reactions. The electron transfer reaction of the surfactant-cobalt(III) complexes was also carried out in a medium of various concentrations of β-cyclodextrin. β-cyclodextrin retarded the rate of the reaction.