A route to magnetically separable nanocatalysts: Combined experimental and theoretical investigation of alkyl substituent role in ligand backbone towards epoxidation ability

We have prepared two chiral Schiff base ligands, H₂L¹ and H₂L², and one achiral Schiff base ligand, H₂L³, by treating 2,6‐diformyl‐4‐methylphenol separately with (R )‐1,2‐diaminopropane, (R )‐1,2‐diaminocyclohexane and 1,1′‐dimethylethylenediamine, in ethanolic medium, respectively. The complexes MnL¹ClO₄ ( 1 ), MnL²ClO₄ ( 2 ), MnL³ClO₄ ( 3 ), FeL¹ClO₄ ( 4 ), FeL²ClO₄ ( 5 ) and FeL³ClO₄ ( 6 ) have been obtained by reacting the ligands H₂L¹, H₂L² and H₂L³ with manganese(III) perchlorate or iron(III) perchlorate in methanol. Circular dichroism studies suggest that ligands H₂L¹ and H₂L² and their corresponding complexes have asymmetric character. Complexes 1 – 6 have been used as homogeneous catalysts for epoxidation of alkenes. Manganese systems have been found to be much better than iron counterparts for alkene epoxidation, with 3 as the best catalyst among manganese systems and 6 as the best among iron systems. The order of their experimental catalytic efficiency has also been rationalized by theoretical calculations. We have observed higher enantiomeric excess product with catalysts 1 and 4 , so they were attached to surface‐modified magnetic nanoparticles to obtain two new magnetically separable nanocatalysts, Fe₃O₄@dopa@MnL¹ and Fe₃O₄@dopa@FeL⁴. They have been characterized and their alkene epoxidation ability has been investigated. These catalysts can be easily recovered by magnetic separation and recycled several times without significant loss of catalytic activity. Hence our study focuses on the synthesis of a magnetically recoverable asymmetric nanocatalyst that finds applications in epoxidation of alkenes and at the same time can be recycled and reused.     

Particle size,morphology, and properties of transition metal ferrospinels of the MFe<Subscript>2</Subscript>O<Subscript>4</Subscript> (M = Co,Ni, Zn) type,produced by glycine-nitrate combustion

Ferrites-spinels of the MFe₂O₄ type (M = Co, Ni, Zn), produced by glycine-nitrate combustion were studied. A physicochemical study of ferrite samples was performed by X-ray fluorescence analysis, scanning electron microscopy, X-ray phase analysis, and X-ray spectroscopy. The average size of the coherent scanning region was found to be (nm): 28 ± 2 for CoFe₂O₄, 32 ± 2 for NiFe₂O₄, and 26 ± 2 for ZnFe₂O₄. Magnetic characteristics were determined by the NMR method. The specific residual magnetization, specific saturation magnetization, and coercive force were, respectively, 14.1 A m² kg^?1, 20.1 A m² kg^?1, 31800 A m^?1 for CoFe₂O₄; 4.4 A m² kg^?1, 23.1 A m² kg^?1, 6550 A m^?1 for NiFe₂O₄; and 5.1 A m² kg^?1, 18.3 A m² kg^?1, 3200 A m^?1 for ZnFe₂O₄. Their magnetic properties show that the resulting ferrospinel powders can be used in the following fields of technology: CoFe₂O₄ in those areas where heat transfer is necessary (hyperthermia) and in development of data storage media; NiFe₂O₄ and ZnFe₂O₄ in those areas where low heat exchange is necessary, ZnFe₂O₄ for fast remagnetization and NiFe₂O₄ as a core or shell for transportation of other substances. The ferrospinel samples compare well in magnetic properties with their foreign commercial analogs, which makes these compounds commercially viable.     

Mass-analyzed threshold ionization spectroscopy of pyrimidine: determining the geometry in the first excited and the ionic ground states

Vibrational spectra of the pyrimidine cation in the electronic ground state were measured via several intermediate states of the first excited state (0⁰,16a¹, 16a², 16a⁴, 16b¹, 10b¹, 6b², 6a¹, 1¹, 4¹, 4² and 12¹) by mass-analyzed threshold ionization spectroscopy. For the first time, several vibrational modes could be assigned in the first excited and the ionic ground states. Anharmonic coupling is shown to occur in the first excited state due to Fermi resonance between the 1¹ and the 16a⁴ vibrations. From the results of the measurements and calculations presented here, pyrimidine is predicted to be planar in the first excited and the ionic ground states, and it belongs to the C_2V point group.     

A matrix-induced change in the electronic ground state of nickel atoms isolated in rare gases

Comparison of the absorption spectra for matrix-isolated Ni atoms with gas-phase data reveals that the electronic ground-state configuration of the isolated atom can be changed by the matrix. While Ni in Ne has the same configuration as in the gas phase, namely 3d⁸4s² we find in Ar, Kr, and Xe the 3d⁹4s¹ configuration to be the ground state. The matrix-induced changes is explained by the repulsive matrix-dopant interaction, which is sufficiently lowered in the 3d⁹4s¹ configuration to overcompensate for the energy difference of 205 cm^?1 by which the 3d⁹4s¹ level lies above the 3d⁸4s² in the free atom.     

Optically detected magnetic resonance study of the phosphorescent states of thiouracils

The triplet states of 1-methyl-2-thiouracil (1-Me-s²U), 1-methyl-4-thiouracil (1-Me-s²s⁴U) and 1-methyl-2,4-dithiouracil (1-Me-s² s⁴) have been investigated by optically detected magnetic resonance in zero magnetic field. The zero field splittings (ZFS) and the individual sublevel kinetic parameters are reported. The ZFS (|D|, |E|) values (in cm^?1) are found to increase in the order: 1-Me-s² U (0.2895, 0.0728) < 1-Me-s⁴U, (0.605, 0.0500) < 1-Me-s²s⁴ U (0.870, 0.0458). The triplet state lifetimes decrease in the same order, and both effects are attributed to an internal heavy atom effect of sulfur substitution. The vibronic structure of the phosphorescence emission indicates that the thiouracil phosphorescent states are ³(π, π^*). The low phosphorescence quantum yields of 1-Me-s⁴ U and of 1-Me-s²s⁴U result from radiationless decay of the triplet state rather than from inefficient intersystem crossing from the excited singlet state. The efficient radiationless decay of the triplet state appears to be a feature of the S-substitution at the 4-position of uracil. Phosphorescence polarization measurements of the individuals triplet sublevel emissions at ca. 1.2 K are consistent with 1-Me-s²U and 1-Me-s⁴U being non-planar in the phosphorescent state; the thiouracil phosphorescence from each triplet sublevel is polarized in the average plane of the distorted molecule. In the absence of σπ separability, spin—orbit mixing of ¹(π, π^*) and ³(π, π^*) states is enhanced and the radiative properties of the triplet state may be dominated by this mechanism rather than by the mixing of ¹(n, π^*), ¹(σ, π^*), or ¹(π, σ^*) with ³(π, π^* states which generally is the dominant mechanism for planar aromatic molecules.     

Solid-State and Solution FT-Raman Spectra of the Tetraiodine Dication I4 2+

Abstract

I₄ ²⁺ is the only known cyclic homopolyatomic cation or anion of iodine. It has a rectangular planar structure which may be thought of as containing two I₂ ⁺ units joined by a weak π?-π? 4 centre 2 electron bond.¹ In this paper we report our FT-Raman spectra of I₄ ²⁺, which conflict with those published by Gillespie et al. ¹ and present evidence that the peaks attributed to a species containing iodine in the +1 oxidation state are in fact due to I₄ ²⁺.     

The spectrophotometric and titrimetric determination of gold with ferroin as reagent

A spectrophotometric and a photometric titration method in a two-phase system for the determination of gold with ferroin is reported. Both methods are rapid and reproducible with an accuracy of ±1%. In the spectrophotometric determination Co²⁺, Cu²⁺, Ni²⁺ , Fe³⁺, Zn²⁺, Mn²⁺ and Cr³⁺ do not interfere with the determination of gold and Pt⁴⁺, Pd²⁺, Hg²⁺, Ir⁴⁺ and Os⁴⁺ can be tolerated up to a ratio of 1:1. The titrations can also be carried out in the presence of a number of diverse ions, e.g. Ni²⁺, Cu²⁺, Co²⁺, Fe³⁺, Zn²⁺, Cr³⁺, Mn²⁺, without interference; the platinum metals and Hg²⁺ cause interference but, by the use of the spectrophotometric procedure, this can be reduced.     

Relative reactivities of heteroaromatic cations towards reduction by 1,4-dihydronicotinamides

Kinetic data are reported for the equilibration of the 1-methyl-3-nitropyridinium cation with its pseudobase (hydroxide adduct) and for the reduction of this cation by 1-benzyl-1, 4-dihydronicotinamide. The C-2 hydroxide adduct is the kinetically controlled product (pK_R+ = 11.6) when this pyridinium cation is mixed with aqueous base, however, this species rearranges to the C-4 adduct as the themodynamically more stable product (pK_R+ = 9.42). The pH-dependence of this equilibration may be analysed to give k_OH = 1600 M^-1s^-1 for hydroxide ion attack at C-4 of this cation. Reduction of this pyridinium cation by 1-benzyl-1, 4-dihydronicotinamide appears to occur exclusively at C-4 with second-order rate constant k₂ = 0.72 M^-1s^-1 and k₂ ^H/k₂^D = 2.0 in 20% CH₃CN - 80% H₂O, ionic strength 1.0, 25°C.The reactivities of pyridinium, quinolinium, isoquinolinium, acridinium and phenanthridinium cations of pK_R+ = 10.0 towards both hydroxide ion and 1-benzyl-1, 4-dihydronicotinamide are evaluated. Relative reactivities (K₂/K_OH) for these two processes are shown to be acridinium : quinolinium (C-4) : pyridinium (C-4) : quinolinium (C-2) : isoquinolinium : phenanthridinium = 1.6×10⁵ : 3400 : 80 : (4 : 1.0 : 0.7 for predominantly aqueous reaction media. These data support the hypothesis that formation of 1, 2-dihydropyridine systems upon reduction of heteroaromatic cations by 1, 4-dihydronicotinamides occurs via direct one step hydride transfer, while formation of 1,4-dihydro-pyridines in such processes occurs preferentially by a mechanistica11y more complex process involving electron transfer.     

Chelate von Chinolin-8-ol — Derivaten. XI. Eigenschaften und Struktur von Nickelchelaten alkyl-substituierter Chinolin-8-ole bzw. Chinolin-8-thiole

Reactions of 1,1,3,3-Tetrakis(dimethylamino)-1λ⁵,3λ⁵-diphosphete with N? H and P? H Acidic Compounds 1,1,3,3-Tetrakis(dimethylamino)-1λ⁵,3λ⁵-diphosphete, 1 , reacts with aniline to give by opening of the ring 2,2,4,4-tetrakis(dimethylamino)-1-phenyl-1,2λ⁵,4λ⁵-azadiphosphapenta-1,3-diene, 2 , with p-CN? C₆F₄? NH₂ the product is 1-(4-cyano-2,3,5,6-tetrafluorophenyl)-2,2,4,4-tetrakis(dimethylamino)-1,2λ⁵,4λ⁵-azadiphosphapenta-1,3-diene, 3 . t-Butylamine or diethylamine do not react with 1 . Mesitylphosphane opens the ring system 1 forming by reduction of one phosphorus atom {[bis(dimethylamino)phosphanyl]methylidene}bis(dimethylamino)methylphosphorane, 4 . The same product 4 is obtained by reaction with phenylphosphane. The reaction products 2–4 are characterized by their nmr, mass, and ir spectra. Their way of formation is discussed. In 4 a ⁵J(PH), in 3 a ⁷J(CF) long range coupling constant could be identified.     

A 3D Adenine-based Cd-MOF: Synthesis,Structure and Photoluminescent Sensing for an Aromatic Azo Compound

A new Cd-MOF containing the nucleobase adenine and multicarboxylates, Cd₂(tdc)₂(1H-ade)₂(H₂O) (H₂tdc = 2,5-thiophene carboxylic acid, 1H-ade = adenine), was synthesized successfully under hydrothermal condition and characterized by single-crystal X-ray diffraction, infrared spectrum, thermogravimetric analysis and photoluminescence. The two crystallographically unsymmetrical Cd atoms are bridged by 2,5-tdc ligands with (κ¹-κ¹)-(κ¹)-μ₃ and (κ¹–κ¹)–μ₂ modes into two dimensional extended layers, which are further pillared with the neutral ade molecules to form a 3D frameworks stabilized by extensive π ··· π interactions between imidazole-, pyrimidine- and thiophene-rings. Inspection of the structure reveals that the architecture can be simplified as a 3,4,5- connected networks with a Schläfli symbol of (6² · 8)(4² · 6³ · 8)(4² · 6⁵ · 8³). The photochemical property shows that the luminescent emission can be significantly quenched by aromatic azo compounds. The quenching effect coefficient (K_sv) for bis(4-imidazol-1-yl-phenyl)diazene is determined to be 4.1 × 10⁴ m ^–1, indicating the title compound as a potential fluorescent sensing materials.     

Chiral Supramolecular Switches Based on (R)‐Binaphthalene–Bipyridinium Guests and Cucurbituril Hosts

We designed and synthesized the three molecular tweezers 1 a – c ⁴⁺ containing an electron acceptor 4,4′‐bipyridinium (BPY²⁺) unit in each of the two arms and an (R)‐2,2′‐dioxy‐1,1′‐binaphthyl (BIN) unit that plays the role of chiral centre and the hinge of the structure. Each BPY²⁺ unit is connected to the BIN hinge by an alkyl chain formed by two‐ ( 1 a ⁴⁺), four‐ ( 1 b ⁴⁺), or six‐CH₂ ( 1 c ⁴⁺) groups. The behavior of 1 a – c ⁴⁺ upon chemical or photochemical reduction in the absence and in the presence of cucurbit[8]uril (CB[8]) or cucurbit[7]uril (CB[7]) as macrocyclic hosts for the bipyridinium units has been studied in aqueous solution. A detailed analysis of the UV/Vis absorption and circular dichroism (CD) spectra shows that the helicity of the BIN unit can be reversibly modulated by reduction of the BPY²⁺ units, or by association with cucurbiturils. Upon reduction of 1 a – c ⁴⁺ compounds, the formed BPY^{+ .} units undergo intramolecular dimerization with a concomitant change in the BIN dihedral angle, which depends on the length of the alkyl spacers. The alkyl linkers also play an important role in association to cucurbiturils. Compound 1 a ⁴⁺, because of its short carbon chain, associates to the bulky CB[8] in a 1:1 ratio, whereas in the case of the smaller host compound CB[7] a 1:2 complex is obtained. Compounds 1 b ⁴⁺ and 1 c ⁴⁺, which have longer linkers, associate to two cucurbiturils regardless of their sizes. In all cases, association with CB[8] causes an increase of the BIN dihedral angle, whereas the formation of CB[7] complexes causes an angle decrease. Reduction of the CB[8] complexes results in an enhancement of the BPY^{+ .} dimerization with respect to free 1 a – c ⁴⁺ and causes a noticeable decrease of the BIN dihedral angle, because the BPY^{+ .} units of the two arms have to enter into the same macrocycle. The dimer formation in the CB[8] complexes characterized by a 1:2 ratio implies the release of one macrocycle showing that the binding stoichiometry of these host–guest complexes can be switched from 1:2 to 1:1 by changing the redox state of the guest. When the reduction is performed on the CB[7] complexes, dimer formation is totally inhibited, as expected because the CB[7] cavity cannot host two BPY^{+ .} units.     

Fermi resonances in the Raman spectra of alkali halide/BH4−

Raman spectra of a series of alkali-halide/BH^?₄ (and BD^?₄ crystals have been obtained. These spectra show some interesting examples of Fermi resonance type interactions between the stretching mode levels and overtone and combination band levels of the bending modes. Two resonances will be considered: (i) that between ν₁ and 2ν₄(A₁), and (ii) that between ν₃, 2ν₄ (F₂) and (ν₂+ν₄) (F₂).The F₂ resonance between ν₃, 2ν₄ and ν₂+ν₄ appears in the infrared spectrum and it has been studied on several occasions. However the equivalent Raman spectrum is of interest because the relative intensities of the bands are significantly different to those shown by the infrared spectrum.In the A₁ (and E) Raman spectrum of the stretching mode region there are two strong bands for each for the ¹⁰B and ¹¹B isotopes. The ν₁ would not be expected to show any ¹⁰B and ¹¹B splitting, but the observed bands are both closely resonating mixtures of ν₁ and 2ν₄(A₁). In fact the analysis shows that the stronger band has the higher proportion of 2ν₄ character, and the larger isotopic shift of the more intense band can then be seen to be reasonable.     

Multifunctional polythreading coordination polymers: spontaneous resolution, nonlinear-optic, and ferroelectric properties

The reactions of methylenediisophthalic acid (H₄L) and N‐auxiliary ligands (1,2‐bis(4‐pyridyl)ethylene, 1,2‐bis(4‐pyridyl)ethane) with transition‐metal centers (Co²⁺/Mn²⁺) have given rise to four unprecedented polythreading coordination polymers. Single‐crystal X‐ray diffraction analyses revealed that the compounds can be described as 3D^2??2[1D²⁺]+2D^6? for 1 , 3D^4??1D²⁺+1D^6? for 2 , and 2D^4??0D²⁺+2[1D^3?] for 3 and 4 . All the polymers are formed through the assembly of two kinds of motifs with opposite charges. Noncentrosymmetric structures and multifunctionality in 2 – 4 are established by varying ligands and metal centers. Spontaneous resolution upon crystallization occurred in compounds 3 and 4 in the absence of any chiral source. The enantiomers of 3 and 4 consist of three chiral building blocks of L^4?/HL^3? and Mn²⁺ centers. In the solid state, polar compounds 2 – 4 exhibit nonlinear‐optic (NLO) and ferroelectric properties at room temperature. The assembly of two kinds of motifs with opposite charges provides a useful method for the preparation of multifunctional compounds.     

Synthesis and structure of alkyl 2-arylsulfanyl-3-nitroacrylates

Alkyl 2-arylsulfanyl-3-nitroacrylates were synthesized by the conjugate Michael addition of thiophenols to alkyl 3-bromo-3-nitroacrylates followed by elimination of HBr on treatment with Et₃N. When treated with 4-chlorothiophenol in the presence of Et₃N, alkyl 2-[(4-chlorophenyl) sulfanyl]-3-nitroacrylates can be transformed into alkyl 2,3-bis[(4-chlorophenyl)sulfanyl]- acrylates. The structures of the synthesized compounds were characterized by IR, UV, ¹H and ¹³C{¹H} NMR spectroscopy using ¹H–¹³C HMQC, ¹H–¹³C, and ¹H–¹⁵N HMBC techniques. Methyl 2-[(4-methylphenyl)sulfanyl]-3-nitroacrylate exists as the Z-isomer, as confirmed by X-ray diffraction.     

A dipyrenyl calixazacrown chemosensor for Mg

A new fluorogenic calix[4]tetraaza-crown-6 (4) bearing two pyrene amide groups has been prepared. It was shown to be selective for Mg²⁺. When Mg²⁺ is bound to 4, the pyrene monomer emission increased while the excimer emission declined in a ratiometric manner. It is shown by ¹H NMR that this ratiometric change is due to the conformational changes of the pyrenes during the chelation of Mg²⁺ by the amide functions to form a 1:1 complex.     

Hydrogen and Methane Production, Energy Recovery, and Organic Matter Removal from Effluents in a Two-Stage Fermentative Process

This study evaluates the potential for using different effluents for simultaneous H₂ and CH₄ production in a two-stage batch fermentation process with mixed microflora. An appreciable amount of H₂ was produced from parboiled rice wastewater (23.9?mL g^?1 chemical oxygen demand [COD]) and vinasse (20.8?mL g^?1 COD), while other effluents supported CH₄ generation. The amount of CH₄ produced was minimum for sewage (46.3?mL g^?1 COD), followed by parboiled rice wastewater (115.5?mL g^?1 COD) and glycerol (180.1?mL g^?1 COD). The maximum amount of CH₄ was observed for vinasse (255.4?mL g^?1 COD). The total energy recovery from vinasse (10.4?kJ g^?1 COD) corresponded to the maximum COD reduction (74.7?%), followed by glycerol (70.38?%, 7.20?kJ g^?1 COD), parboiled rice wastewater (63.91?%, 4.92?kJ g^?1 COD), and sewage (51.11?%, 1.85?kJ g^?1 COD). The relatively high performance of vinasse in such comparisons could be attributed to the elevated concentrations of macronutrients contained in raw vinasse. The observations are based on kinetic parameters of H₂ and CH₄ production and global energy recovery of the process. These observations collectively suggest that organic-rich effluents can be deployed for energy recovery with sequential generation of H₂ and CH₄.     

Synthesen von Verbindungen mit M–N‐Bindungen (M = Li,Ga, In)

Syntheses of Compounds with M–N Bonds (M = Li, Ga, In) The adducts [GaCl₃(HNⁱPr₂)] ( 1 ) and [InCl₃{HN(CH₂Ph)₂}₂] ( 2 ) can be obtained by the reactions of the corresponding metal(III) halides with the amines. The In amide In(N^cHex₂)₃ ( 3 ) can be formed by treatment of InCl₃ with three equivalents of LiN^cHex₂. Reaction with four equivalents of LiN^cHex₂ leads to the same product. However, the treatment of InCl₃ with four equivalents of LiN(CH₂Ph)₂ gives the desired metalate [Li(THF)₄][In{N(CH₂Ph)₂}₄] ( 4 ). From the corresponding reaction of InCl₃ with LiNⁱPr₂ no In‐containing product could be identified. Instead, the aggregate of LiCl with three units of LiNⁱPr₂, [Li₄(NⁱPr₂)₃(THF)₄Cl] ( 5 ), was isolated. 1 – 4 were characterized by NMR, IR and MS techniques as well as by X‐ray structure determinations. According to them, 1 possesses a tetrahedrally coordinated Ga atom, at which two units of 1 are connected by hydrogen bridges to centrosymmetrical dimers. The In atoms in 2 have a trigonal‐bipyramidal coordination sphere; the amine molecules occupy the apical positions. The central metal atom in 3 and the anion of 4 exhibit trigonal‐planar and distorted tetrahedral environments, respectively. The novel structural motif in 5 is the Cl^– ion, only partly surrounded by Li⁺ ions in a strongly distorted trigonal‐bipyramidal fashion. The dominating angle amounts to 165.2(2)°.     

Reactions of Copper(II) Chloride in Solution: Facile Formation of Tetranuclear Copper Clusters and Other Complexes That Are Relevant in Catalytic Redox Processes

Mixing CuCl₂ ? 2 H₂O with benzylamine in alcoholic solutions led to an extremely colorful chemistry caused by the formation of a large number of different complexes. Many of these different species could be structurally characterized. These include relatively simple compounds such as [Cu(L¹)₄Cl₂] (L¹=benzylamine) and (HL¹)₂[CuCl₄]. Most interestingly is the easy formation of two cluster complexes, one based on two cluster units Cu₄OCl₆(L¹)₄ connected through one [Cu(L¹)₂Cl₂] complex and one based on a cubane‐type cluster ([Cu₄O₄](C₁₁H₁₄)₄Cl₄). Both clusters proved to be highly reactive in a series of oxidation reactions of organic substrates by using air or peroxides as oxidants. Furthermore, it was possible to isolate and structurally characterize ([Cu(L¹)Cl]₃ and [Cu(benz₂mpa)₂]CuCl₂ (benz₂mpa=benzyl‐(2‐benzylimino‐1‐methyl‐propylidene)‐amine), two copper(I) complexes that formed in solution, demonstrating the high redox activity of the cluster systems. In addition, it was possible to solve the molecular structures of the compounds Cu₄OCl₆(MeOH)₄, [Cu(MeOH)₂Cl₂], [Cu(aniline)₂Cl₂], and an organic side product (HC₁₃H₁₉NOCl). In fact all determined structures are of a known type but the chemical relation between these compounds could be explained for the first time. The paper describes these different compounds and their chemical equilibria. Some of these complexes seem to be relevant in catalytic oxidation reactions and their reactivity is discussed in more detail.     

Synthesis of (2-hydroxo-5-chlorophenylaminoisonitrosoacetyl)phenyl ligands and their complexes: Spectral,thermal and solvent-extraction studies

Four different types of new ligands Ar[COC(NOH)R] _n (Ar=biphenyl, n = 1 H₂L¹; Ar=biphenyl, n = 2 H₄L²; Ar=diphenylmethane, n = 1 H₂L³; Ar=diphenylmethane, n = 2 H₄L⁴; R=2-amino-4-chlorophenol in all ligands) have been obtained from 1 equivalent of chloroketooximes Ar[COC(NOH)Cl] _n (HL¹-H₂L⁴) and 1 equivalent of 2-amino-4-chlorophenol (for H₂L¹ and H₂L³) or 2 equivalent of 2-amino-4-chlorophenol (for H₄L² and H₄L⁴). (Mononuclear or binuclear cobalt(II), nickel(II), copper(II) and zinc(II) complexes were synthesized with these ligands.) These compounds have been characterized by elemental analyses, AAS, infra-red spectra and magnetic susceptibility measurements. The ligands have been further characterized by ¹H NMR. The results suggest that the dinuclear complexes of H₂L¹ and H₂L³ have a metal:ligand ratio of 1:2; the mononuclear complexes of H₄L² and H₄L⁴ have a metal:ligand ratio of 1:1 and dinuclear complexes H₄L² and H₄L⁴ have a metal:ligand ratio of 2:1. The binding properties of the ligands towards selected transition metal ions (Mn^II, Co^II, Ni^II, Cu^II, Zn^II, Pb^II, Cd^II, Hg^II) have been established by extraction experiments. The ligands show strong binding ability towards mercury(II) ion. In addition, the thermal decomposition of some complexes is studied in nitrogen atmosphere.     

Anion-exchange separation of Pt and Pd using perchloric and hydrochloric acid solutions

On Biorad Ag-1X8 anion-exchange resin (200–400 mesh), Pd and Pt may be separated from one another by elution with 0.2M HClO₄, and 5M HClO₄, respectively. If present, Au may be retained by making the elutriants 0.003M in HCl. Alternatively, reduction by H₂SO₃ enables elution of Pt²⁺ with 6M HCl before recovery of Pd²⁺ with 0.2M HClO₄·Ir⁴⁺ is reduced to Ir³⁺ by H₂SO₃ and may be eluted ahead of Pt²⁺ by 2M HCl.