COMPLEXATION OF METAL IONS WITH 3,5-DI-TERT-BUTYL-1,2-BENZOQUINONE-1-MONOOXIME,ESR STUDIES OF RADICAL INTERMEDIATES

Abstract

The possibility of chelate formation of 3,5-di-terf-butyl-o-benzoquinone-1-monooxime with Cu(II), Co(II), Ni(II), Mn(II), Pd(II) metal ions under N₂ and in air have been investigated. It was found that complexation of metals except Cu(II) and Mn(II) was accompanied by formation of various stable radical species under air. The complexation of Co(II) even under N₂ unlike other metal ions, results in the formation of very stable radical species, which are assigned to phenazinyl type radical. ESR examination of reduction of bis(3,5-di-tert-butyl-o-benzoquinone-1-monooximato)M(II) (M = Cu, Pd) with triarylphosphines P(C₆H₄ X)₃ (X = H, m-Cl, m-CH₃, p-Et₂N) reveal the formation of the N-(2′-hydroxy-3,5-di-tertbutylphenyl)-4′,6′-di-tertbutyl-o-benzosemiquinone iminate radical. Finally, ESR spectra of Cu(II), Ni(II), and Mn(II) complexes at 300 and 130 K, as well as reaction of bis(oximato)Ni(II) with PPh₃ have been studied.     

Acute Toxicity of Cresols to Pseudomonas — An Initial Oxygen Uptake Method

Acute toxicity of cresols to both Pseudomonas I and II was estimated by an initial oxygen uptake method. Inhibition studies of toluene and cresols on the oxidation of either benzoate by Pseudomnas I or phenol by Pseudomonas II were analyzed and expressed as oxygen uptake rates. Double reciprocal plots for the inhibiton by cresols of oxygen uptake in Pseudomonas, two physical constants, Vmaxi and Ki, were obtained. The Vmaxi of o?, m? and p-cresol were 80%, 81% and 57% of Vmax in Pseudomnas I, and 10%, 25% and 36% in Pseudomonas II, respectively. Thus, the toxicity to Pseudomonas I decreases in the order p- > o- ≥ m-cresol, whereas to Pseudomonas II, the order is changed to o- > m- > p-cresol. This difference in the toxicity order is probably due to the allosteric effect of p-cresol towards Pseudomonas II. Inasmuch as most compounds inhibit noncompetively, the relative toxicity of different compounds can be estimated by a new toxicity parameter RI (relative inhibition) which is defined as 100/Ki. By comparing the RI value of each compound, the toxicity to Pseudomonas I decreases in the order m-chlorophenol > p-cresol > p-chlorophenol > o-cresol ≥ m-cresol > o-chlorophenol > toluene > phenol.     

Infrared spectral studies on the stability of some binuclear transition metal—Schiff base complexes

Some di-Schiff bases like N,N′-o-phenylene-bis-salicylaldimine (DSB₁), N,N′-m-phenylene-bis-salicylaldimine (DSB₂) and N,N′-p-phenylene-bis-salicylaldimine (DSB₃) have been synthesized by the condensation of salicylaldehyde with o-, m- and p-phenylenediamines, respectively. The synthesized complexes of Cu(II), Ni(II) and Co(II) with these ligands have been assigned their molecular structure on the basis of their elemental analyses, molecular weight determination, magnetic measurements, electronic spectra, molar volume and infrared spectral studies. The nature of bonding between metal ion and Schiff bases is studied by i.r. spectrophotometry. The shift in the band position of the groups involved in coordination has been utilized to estimate the coordination bond lengths. The value of the coordination bond length of Cu(II) complexes is shorter than the corresponding values for Ni(II) and Co(II) complexes.     

Thermal, spectral and magnetic characterization of Co(II), Ni(II) AND Cu(II) 4-chloro-2-nitrobenzoates

Physico-chemical properties of 4-chloro-2-nitrobenzoates of Co(II), Ni(II), and Cu(II) were studied. The complexes were obtained as mono- and trihydrates with a metal ion to ligand ratio of 1:2. All analysed 4-chloro-2-nitrobenzoates are polycrystalline compounds with colours depending on the central ions: pink for Co(II), green for Ni(II), and blue for Cu(II) complexes. Their thermal decomposition was studied only in the range of 293–523 K, because it was found that on heating in air above 523 K 4-chloro-2-nitrobenzoates decompose explosively. Hydrated complexes lose crystallization water molecules in one step and anhydrous compounds are formed. The final products of their decomposition are the oxides of the respective transition metals. From the results it appears that during dehydration process no transformation of nitro group to nitrite takes place. The solubilities of analysed complexes in water at 293 K are of the order of 10^–4–10^–2 mol dm^–3. The magnetic moment values of Co²⁺, Ni²⁺ and Cu²⁺ ions in 4-chloro-2-nitrobenzoates experimentally determined at 76–303 K change from 3.89 to 4.82 μ_B for Co(II) complex, from 2.25 to 2.98 μ_B for Ni(II) 4-chloro-2-nitrobenzoate, and from 0.27 to 1.44 μ_B for Cu(II) complex. 4-chloro-2-nitrobenzoates of Co(II), and Ni(II) follow the Curie–Weiss law. Complex of Cu(II) forms dimer.     

Magnetic, spectral, and thermal behaviour of 2-chloro-4-nitrobenzoates of Co(II), Ni(II), and Cu(II)

Some physicochemical properties of 2-chloro-4-nitrobenzoates of Co(II), Ni(II), and Cu(II) were studied. The complexes were obtained as mono-and dihydrates with a metal ion—ligand mole ratio of 1: 2. All complexes are polycrystalline compounds. Their colours depend on the kind of central ion: pink for Co(II) complex, green for Ni(II), and blue for Cu(II) complexes. Their thermal decomposition was studied only in the range of 293 K–523 K because it was found that on heating in air above 523 K 2-chloro-4-nitrobenzoates decompose explosively. Hydrated complexes lose crystallization water molecules in one step. During dehydration process no transformation of the nitro group to nitrito one took place. Their solubilities in water at 293 K are of the orders of 10⁻³-10⁻² mol dm⁻³. The magnetic moment values of 2-chloro-4-nitrobenzoates determined in the range of 76 K–303 K change from 3.48μ_B to 3.82μ_B for Co(II) complex, from 2.24μ_B to 2.83μ_B for Ni(II) 2-chloro-4-nitrobenzoate, and from 0.31μ_B to 1.41μ_B for Cu(II) complex. 2-Chloro-4-nitrobenzoates of Co(II) and Ni(II) follow the Curie—Weiss law, but the complex of Cu(II) forms dimer.     

Lead Determination by Anodic Stripping Voltammetry Using a p‐Phenylenediamine Modified Carbon Paste Electrode

Carbon paste electrodes were modified by mixing appropriate amounts of the monomers o‐phenylendiamine, p‐phenylendiamine and m‐phenylendiamine (o‐PD, p‐PD and m‐PD) into a graphite powder‐paraffin oil matrix. The electropolymerization of the incorporated phenylendiamine was then carried out in a carbon paste electrode in acidic medium by cyclic voltammetry between ?0.30 V and +0.90 or under constant potential. The modified carbon paste electrodes (MCPEs) obtained by this electropolymerization method were found to be useful for trace determination of Pb²⁺ in aqueous solutions. Lead(II) was first preconcentrated on the modified electrodes by complexation with the modifier, and the electrode was then transferred to an electrochemical cell. The best results in terms of sensitivity and detection limit were obtained with poly p‐phenylenediamine (poly (p‐PD)). For a 10‐min preconcentration time, the calibration plot was linear from 5×10^?8 mol L^?1 to 10^?5 mol L^?1, with r²=0.999 and relative standard deviation equal to 5%. However, the lowest lead concentration that could be detected was 10^?9 mol L^?1. Interference from metal ions like Cd(II), Hg(II), Zn(II), Fe(II) and Cu(II) was also studied.     

On Attempted Oxidative Cyclisation of Isomeric N,N'-Diphenylphenylenediamines and Their N,N'-Dimethyl Derivatives by Palladium(II) Acetate and Uv Light

The cyclisation of N,N'-diphenyl-o-, m- and p-phenylenediamines and their N,N'-dimethyl derivatives by palladium(II) acetate and UV light separately led to both bis-cyclisation, furnishing indolocarbazoles, and mono-cyclisations with cleavage as well as retention of one substituent, producing substituted carbazoles.     

The Stabilities of the o-Carboxyphenylhydrazo-Ethylacetoacetate OF Cu,Ni, Co,Zn, Mn and Cd Chelate Compounds in Different Solvents

The dissociation constants for o-carboxyphenylhydrazoethylacetoacetate (o-CPHEA) ligand, as well as the stability constants for the divalent metal complexes of Cu, (II), Ni (II), Co (II), Zn (II)and Cd (II) ions, have been calculated pH-meterically in different solvents. The dissociation constans pK₁=4.10 and pK₂=10.55 of the insoluble organic ligand are calculated in aqueous medium. The effect of solvents, the relation between stabilities and both electronegativities and ionization potential are studied.     

Radical polymerization behavior of hydroxystyrenes

Homopolymerizations of m- and p-hydroxystyrene and their copolymerizations with styrene and methyl methacrylate by use of azobisisobutyronitrile as initiator were investigated, and the results were compared with those obtained previously o-hydroxystyrene. Intrinsic viscosities of m- and p-hydroxystyrene polymers obtained by bulk and solution polymerizations were ca. 2 to 3 times larger than those of o-hydroxystyrene polymers obtained by the similar conditions. The structures of the polymers thus produced were investigated by infrared and ultraviolet spectroscopy. These studies suggested that all of the homopolymers consisted mainly of structures of normal vinyl type polymer. R_p was proportional to [I]^0.52 for m-hydroxystyrene and to [I]^0.50 for p-hydroxystyrene, for o-hydroxystyrene R_p was proportional to [I]^0.72. A reasonable chain transfer mechanism for these monomers was postulated. The apparent activation energies of polymerization for m- and p-hydroxystyrene were found to be 20.1, and 18.0 kcal/mole, respectively, compared to the value of 21.5 kcal/mole for o-hydroxystyrene. Monomer reactivity ratios and Q ? e values for m- and p-hydroxystyrene were determined, and the results were also compared with the case of o-hydroxystyrene. Copolymerization generally gave a polymer with relatively high intrinsic viscosity, even in the case of o-hydroxystyrene.     

N-Glucosides of Aminobenzoic Acids and Aminophenols

N-o-, -m-, and -p-carboxyphenyl-D-glucosylamines and N-o-, -m-, and -p-hydroxyphenyl-D-glucosylamines were synthesized by reaction of D-glucose with o-, m-, and p-aminobenzoic acids and o-, m-, and p-aminophenols. It was demonstrated that both - and -anomers were formed by N-glycosylation of o-, m-, and p-aminobenzoic acids; only -anomers, by N-glycosylation of o-, m-, and p-aminophenols.     

Morphology-dependent luminescence properties of poly(benzyl ether) dendrimers

Poly(benzyl ether) dendrimers with o-, m-, and p-isomers of dialkoxybenzene at their focal points [o-, m-, and p-(Gn)₂Ar], having generation numbers (n) of 0–3, were synthesized. ¹H NMR pulse relaxation times (T₁) of the exterior MeO groups of o- and m-(Gn)₂Ar (n = 0–3) all remained in the range of 0.92–1.43 s. In sharp contrast, an exceptionally short T₁ value (0.23 s) was observed for p-(G3)₂Ar. Although their absorption spectral profiles were slightly different from one another, an essential difference was observed for their fluorescence properties. When the generation number was increased, the fluorescence efficiency of o-(Gn)₂Ar increased, but that of p-(Gn)₂Ar decreased, whereas m-(Gn)₂Ar exhibited a relatively small change in the fluorescence efficiency. Fluorescence depolarization studies showed a highly efficient intramolecular energy migration in p-(G3)₂Ar as compared with o-(G3)₂Ar and m-(G3)₂Ar. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3524–3530, 2003     

Chelating Behaviour of Substituted 1-Benzoyl-4-Phenylthiosemicarbazide

The preparation and characterization of a series of new coordination compounds of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) containing o-methyl- or o-chlorobenzoyl-4-phenyl-3-thiosemicarbazide (HMBPT, HCBPT=HL) are reported. The reaction products were investigated by analyses, electrolytic conductance, magnetic susceptibility, reflectance and IR spectral studies. The IR spectra show that HMBPT and HCBPT coordinate with the metal ions via different coordination sites (NS and/or NO). The spectral data support the suggestion that the ligands form his-chelates with Ni(II) and Cu(II) of square planar stereochemistry and of general formulae ML₂·H₂O, where L is the uninegatively charged bidentate ligand. The Co(II) ion forms octahedral and tetrahedral structures with HMBPT and HCBPT, respectively. The ligand field parameters (D₄, B and β) for the Co(II) chelates were calculated using the averaged-ligand-field approximation. The influence of the benzene ring substituents (o-chloro or o-methyl) on the stereochemistry are discussed. Also, the formation of the complexes in solution was tested by the pH-metric method.     

Linear free energy relationships between stability of complex and basicity of ligand: VII. The copper(II)-heteronuclear aromatic base-aminoacid ternary systems

The formation constants of ternary mixed ligand complex compounds formed from Cu(II)-2,2′-bipyridyl (bipy) with N-(para-substituted phenyl) glycines (pRPhG), Cu(II)-1,10-phenanthroline (phen) with N-(meta-substituted phenyl) glycines (mRPhG), Cu(II)-bipy/phen with some α-aminoacids (αA) have been determined by pH method at 25°C in the presence of 0.10 M NaClO₄. It was found that linear free energy relationships do exist between the stability of ternary complex compounds and the base strengths of the ligands in all four ternary systems investigated. The stability of the ternary complex compounds was discussed in terms of ΔlogK_M and log X values. It was found again that linear relationships exist between Δ log K_M, log X and pK₂ in the Cu(II)-phen-mRPhG ternary system.     

On the structure of negative ions formed by dissociative electron attachment by monochlorophenol molecules

The energetics of negative ion formation by resonant dissociative electron attachment by o-, m-, and p-chlorophenol molecules was studied. The structures of some fragment ions and their neutral partners were established. Hidden rearrangement processes leading to the formation of oxy anions by the detachment of chlorine atoms from molecular ions were found. The O—H bond dissociation energies for o-, m-, and p-chlorophenol molecules were 3.74±0.11, 3.72±0.17, and 3.94±0.11 eV, respectively.     

Novel metal-based antimicrobial agents of copper(II) complexes: Synthesis,spectral characterization and DNA interaction study

Few novel mixed ligand copper(II) complexes of the type [Cu(L)(Cl)₂(H₂O)], [Cu(L)₂]Cl₂, [Cu(L)L¹] and [Cu(L)(phen)H₂O]Cl₂ (where L is the ligand obtained from the condensation of N-(2-aminoethyl)-1,3-propanediamine with m-nitrobenzaldehyde (L_a)/o-chlorobenzaldehyde (L_b)/benzaldehyde (L_c)/p-methoxybenzaldehyde (L_d)/p-hydroxybenzaldehyde (L_e)/furfuraldehyde (L_f)/pyrrole-2-carboxaldehyde (L_g); L¹ is another ligand obtained from the condensation of anthranilic acid with salicyaldehyde; phen = 1,10-phenanthroline) have been synthesized and characterized by the spectral and analytical techniques. From these data, it is found that the ligands adopt distorted octahedral geometry on metalation with Cu(II) ion. The XRD data indicate that the complexes are polycrystalline with nanosized grains. The SEM images of [Cu(L_a)phen(H₂O)]Cl₂ and [Cu(L_f)₂]Cl₂ complexes show that they have leaf and cauliflower like morphology. The in vitro biological screening effects of the investigated compounds have been tested against the bacteria such as Escherichia coli, Klebsiella pneumoniae, Salmonella typhi, Pseudomonas aeruginosa and Staphylococcus aureus and fungi such as Aspergillus niger, Rhizopus stolonifer, Aspergillus flavus, Rhizoctonia bataicola and Candida albicans by the well diffusion method. A comparative study of MIC values of the Schiff base ligands and their complexes indicates that the complexes exhibit higher antimicrobial activity than the free ligands. An electrochemical study of the copper complexes containing electron withdrawing substituted ligands reveals that they prefer to bind to DNA in Cu(II) rather than Cu(I) oxidation state.     

Synthesis and characterization of acetylene-terminated aromatic amide resin precursors

A series of 10 acetylene-terminated aromatic amide monomers was synthesized by the triethylamine-promoted reaction of bis[p-(m-chlorocarbonylphenoxy)phenyl] sulfone or bis[p-(m-chlorocarbonylphenoxyl)phenyl]ketone with o- or p-ethynyl- and o- or p-trimethylsilylethynylaniline. Yields were essentially quantitative. Structures were verified by infrared and nuclear magnetic resonance spectroscopy and mass spectral data. Thermal characteristics of the monomers were investigated by means of differential scanning calorimetry and thermogravimetric analysis. The initial glass transition temperatures were generally well below the onset of cure which occurred in the 160–225°C range for the terminal ethynyl monomers and in the 260–295°C range for their trimethylsilylethynyl analogs. Onset of decomposition in air for the resinified terminal ethynyl monomers took place in the 400–485°C range, while resins from the trimethylsilylethynyl monomers underwent breakdown at substantially lower temperatures.     

Effect of methoxy position on dynamic mechanical and shape memory properties of methoxyphenol-based polybenzoxazines

Abstract

Two series of benzoxazines were synthesized from o-, m-, and p-methoxyphenols, two polyetheramines with different molecular weights, and formaldehyde. The glass transition temperatures (T _gs) of m-methoxyphenol-based polybenzoxazines are respectively higher than those of o- and p-methoxyphenol-based counterparts. The polybenzoxazines exhibit thermally induced one-way dual-shape memory behavior based on T _g, and the o- and p-methoxyphenol-based polybenzoxazines exhibit higher shape memory performance than m-methoxyphenol-based counterparts under motion constraints.     

Nitrosation kinetics of phenolic components of foods and beverages

The kinetics of the reactions between sodium nitrite and phenol or m-, o-, or p-cresol in potassium hydrogen phthalate buffers of pH 2.5–5.7 were determined by integration of the monitored absorbance of the C-nitroso reaction products. At pH > 3, the dominant reaction was C-nitrosation through a mechanism that appears to consist of a diffusion-controlled attack on the nitrosatable substrate by NO⁺/NO₂H₂⁺ ions followed by a slow proton transfer step; the latter step is supported by the observation of basic catalysis by the buffer which does not form alternative nitrosating agents as nitrosyl compounds. The catalytic coefficients of both anionic forms of the buffer have been determined. The observed order of substrate reactivities (o-cresol ≈ m-cresol > phenol ≫ p-cresol) is explained by the hyperconjugative effect of the methyl group in o- and m-cresol, and by its blocking the para position in p-cresol. Analysis of a plot of ΔH^# against ΔS^# shows that the reaction with p-cresol differs from those with o- and m-cresol as regards the formation and decomposition of the transition state. The genotoxicity of nitrosatable phenols is compared with their reactivity with NO⁺/NO₂H₂⁺. © 1997 John Wiley & Sons, Inc.     

The influence of aminobenzoic acid on Zn(II) electroreduction on a mercury electrode in water-methanol

Summary The influence of the isomers of aminobenzoic acid on the reaction Zn(II)/Zn(Hg) was studied in water-methanol mixtures. Theo- andm-isomers accelerate this reaction in all investigated solutions. The standard rate constants are similar at the same degree of electrode coverage with these isomers in water and mixed solutions.p-Aminobenzoic acid inhibits the process of Zn(II)/Zn(Hg) electroreduction. The results suggest that the decisive role in the acceleration is played by the formation of the active complex inside the adsorption layer.

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Der Einfluß von Aminobenzoesäure auf die Elektroreduktion von Zn(II) an einer Quecksilberelektrode in Methanol-Wasser

Zusammenfassung Der Einfluß der verschiedenen Isomeren von Aminobenzoesäure auf die Reduktion von Zn(II) an einer Quecksilberelektrode wurde in Methanol-Wasser-Mischungen untersucht. Dieo- undm-Isomeren beschleunigen die Reaktion, und die Reaktionsgeschwindigkeiten sind in Wasser und in Methanol-Wasser gleich. Die Beschleunigung wird wahrscheinlich durch Bildung des aktivierten Komplexes innerhalb der Adsorptionsschicht verursacht.p-Aminobenzoesäure hemmt die Elektroreduktion.

     

Coordinating Properties of Co(II) and Zn(II) Complexes with Sterically Hindered Porphyrins

Cobalt(II) and zinc(II) complexes with 5,15-di(o-methoxyphenyl)-3,7,13,17-tetramethyl-2,8,12,18-tetra-n-buthylporphyrin and its capped analogues, where the MN₄ reaction site is shielded by bridging groups containing m-phenylene and dimethoxy-substitutedp-phenylene fragments, were synthesized. Equilibrium constants of additional coordination of pyridine and N-methylimidazole by these metalloporphyrins were determined at 298 K. It was found that steric distortion of the porphyrin core destabilizes extra complexes.