New Coordination Polymers of 1,4-Bis(2″-Hydroxyphenylazomethine) Phenylene

Coordination polymers of 1,4-bis(2′-hydroxyphenylazomethine) phenylene have been prepared with the metal ions Ti(III), Cr(III), Fe(III), Mn(II), Ni(II), and Cu(II). They were characterized by elemental analysis, IR, and electronic spectra. The metal contents in all polymers were found to be consistent with a 1:1 (metal:ligand) stoichiometry. The thermal behavior of these coordination polymers has been studied by thermogravimetric analysis in air up to 750°C, and the data showed that they are thermally stable up to 200°C. Physical properties such as the solubility and viscosity of the polymer complexes were also determined. Electrical conductivity measurements of the synthesized polychelated polymers showed that they are insulators except for the Ni(II) complex which shows a semiconducting character. Mössbauer data clearly establish the 3 + oxidation state for the iron complex polymer.     

On the role of the ground state Tb(III)/acetylacetone complex in sensitized emission of Tb(III) in ethanol solution

Summary The Tb(III)-acetylacetone system in ethanol solution has been studied by spectroscopic methods. The formation of a Tb(III)/acetylacetone (1:1) complex in the ground state has been proved and its stability constant determined,K=(0.97±0.06)·10⁴dm³mol^–1. The role of this complex in the spectrofluorimetric determination ofLn(III) ions in the presence of acetylacetone has been discussed.

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Über die Rolle eines Tb(III)-Acetylaceton-Komplexes im Grundzustand in der sensibilisierten Emission von Tb(III) in Ethanol-Lösung

Zusammenfassung Das Tb(III)-Acetylaceton-System in Ethanol-Lösung wurde mit spektroskopischen Methoden untersuchung. Die Bildung eines Tb(III)-Acetylaceton(1:1)-Komplexes im Grundzustand wurde bestätigt und seine Stabilitätskonstante bestimmt,K=(0.97±0.06)·10⁴dm³mol^–1. Die Rolle dieses Komplexes in der spektrofluorimetrischen Bestimmung vonLn(III)-Ionen in Gegenwart von Acetylaceton wurde erörtert.

     

Kinetics of base hydrolysis of tris-(1,10-phenanthroline)iron(II) and of solvolysis of cis-dichlorobis(1,2-ethanediamine)cobalt(III) in water + diol mixtures

Rate constants for base hydrolysis of the tris-(1,10-phenanthroline)iron(II) cation and for solvolysis of the cis-dichlorobis(1,2-ethanediamine)cobalt(III) cation have been measured in binary aqueous mixtures containing 1,2-ethanediol, 1,2- or 1,4-butanediol, 1,2- or 1,6-hexanediol, 1-propanol, or t-butyl alcohol, at 298.2 K. Kinetics of base hydrolysis of the cobalt(III) complex have also been monitored in methanol-water and ethanol-water mixtures, again at 298.2 K. The observed reactivity trends are discussed in terms of the hydrophilic and hydrophobic properties of the respective diols. The dominant factor determining reactivity is hydration of the attacking hydroxide or leaving chloride, as is evidenced by the close correspondence between rate constants and transfer chemical potentials for these anions. The role of hydration has also been probed through the determination of activation volumes for these two reactions in 60% 1,4-butanediol. © 1993 John Wiley & Sons, Inc.     

Structural studies and quantum chemical calculations of Cr(III), Fe(III) and Ru(III) bromazepam complexes

The reaction of bromazepam (7‐bromo‐1,3‐dihydro‐5‐(2‐pyridyl)‐2H ‐1,4‐benzodiazepin‐2‐one, BZM) with Cr(III) ( 1 ), Fe(III) ( 2 ) and Ru(III) ( 3 ) salts gives complexes of the type [M(BZM)₃]⋅3X (X = Cl or NO₃). Structural characterization was extensively carried out using various analytical and spectral tools such as infrared, ¹H NMR and UV–visible spectroscopies and magnetic, conductance, elemental and thermal analyses. BZM is a bidentate ligand and interacts with the metal ions via the pyridine and benzodiazepin‐2‐one nitrogen atoms. The magnetic and electronic properties of 2 and 3 are consistent with low‐spin octahedral complexes. The three BZM molecules are non‐isoenergetically coordinated to the metal ions and this is reflected in the values of the second‐order interaction energy. The antibacterial activity was studied using Staphylococcus aureus and Escherichia coli . Coordination of BZM to Cr(III) or Ru(III) ions leads to a marked increase in toxicity with respect to the inactive Fe(III) complex 2 .     

Synthesis and mass spectral studies of 1-[5-chloro-1-substituted-2(1H)-pyrazin-2-on-3-yl]-5-aryl-3-methylpyrazoles

Sixteen new 1-[5-chloro-1-substituted-2(1H)-pyrazin-2-on-3-yl]-5-aryl-3-methylpyrazoles V have been synthesized by condensation of 5-chloro-1-substituted-3-hydrazino-2(1H)-pyrazin-2-ones III and 1-aryl-1,3-butanediones IV in dry 1,4-dioxane. The general mass spectral fragmentation mode of these compounds has been studied.     

Formation of Diazepam–Lanthanides(III) Complexes in the 50–50 Volume % Ethanol–Water Solvent System and Study of the Effect of Temperature on the Complex Formation Constants

Diazepam (7-chloro-1,3-dihydro-1-methyl-5-phenyl-2H-1,4-benzodiazepin-2-one) is an important derivative of the 1,4-benzodiazepine compound commercially distributed as Valium. The complex formation constants of diazepam with some light lanthanide(III) metal ions have been studied by potentiometric measurements. All titrations were performed in 50–50% (volume/volume) ethanol–water solvent mixtures at constant ionic strength (0.10 mol⋅dm⁻³). The ionic strength was maintained by using sodium perchlorate. The complex formation constants were determined at 25.00, 35.00 and 45.00 °C. With increasing temperature, a decrease was observed in the protonation constant (pK) of diazepam.     

Acid-catalysed,nucleophile-catalysed and thermal decomposition of 2-amino-3-(2′,2′-dimethylaziridino)-1,4-naphthoquinone

The course of the thermal, acid-catalysed and iodide-catalysed decomposition of 2-amino-3-(2′,2′-dimethylaziridino)-1,4-naphthoquinone (III) was investigated. Thermal and iodide-catalysed decompositions gave mainly 2,3-diamino-1,4-naphthoquinone (VI) and 2-amino-3-(2′-methylallylamino)-1,4-naphthoquinone (V) together with low amounts of 2,2-dimethyl-1,2,3,4,5,10-hexahydrobenzo[g]quinoxaline (IV) and 2-isopropyl-1H-naphthoimid-azole-4,9-dione (VII). The acid catalysed isomerization of the aziridinonaphthoquinone III with halohydric acids or with acetic acid readily gave the opening of the aziridine ring; the corresponding salts of 2-amino-3-(2′-haloisobutylamino)-1,4-naphthoquinones (VIIIa-c) and 2-amino-3-(2′-acetoxyisobutylamino)-1,4-naphthoqunone (X) were formed by cleavage of the carbon-nitrogen bond at the substituted carbon atom. Hypotheses on the mechanism of these reactions are given.     

Spectroscopic studies on charge-transfer complexes formed in the reaction of ferric(III) acetylacetonate with sigma- and pi-acceptors

The reaction of ferric(III) acetylacetonate (donor), Fe(acac)3, with iodine as a sigma-acceptor and with other different pi-acceptors have been studied spectrophotometrically at room temperature in chloroform. The pi-acceptors used in this investigation are 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), p-chloranil and 7,7',8,8'-tetracyanoquinodimethane (TCNQ). The results indicate the formation of 1:1 charge-transfer complexes with a general formula, [Fe(acac)3 (acceptors)]. The iodine complex was shown to contain the triiodide species, [Fe(acac)3]2I(+)I3-, based on the electronic absorptions as well as on the Far-infrared absorption bands characteristic for the non-linear triiodide species, I3-, with C2v symmetry. The proposed structure of this complex is further supported by thermal and middle infrared measurements.     

Spectrophotometric Determination of Iron (III) Using 3-Hydroxy-2-Methyl-1,4-Naphthoquinone Monoxime (HMNQM)

Iron (III) forms brown coloured complex with 3-hydroxy-2-methyl-1,4-naphthoquinone monoxime. The iron (III)-HMNQM complex is found to be soluble in DMF and exhibits maximum absorption at 470 nm in the pH range 4.5–5.5. Beer's law is obeyed upto 5.58 ppm of iron (III) and sensitivity of the reaction is 0.0046 μg/cm², with molar absorptivity of 1.21×10⁴ ? mole^?1 cm^?1. The method has been used for the determination of iron (III) in alloys.     

Die Schmidtreaktion am 1-Methyl-3-phenylpiperidon-(4)

Zusammenfassung 1-Methyl-3-phenylpiperidon-(4) (I) gab bei derSchmidt-Reaktion 1-Methyl-6-phenyl-1,4-diazacycloheptanon-(5) (III), dessen Struktur durchHofmann-Abbau des Methojodides (V) und Hydrolyse des Abbauproduktes (VI) zu Atropasäure und asym. Dimethyläthylendiamin bewiesen wurde. Das Lactam (III) wurde mit LiAlH₄ in das 1-Methyl-6-phenyl-1,4-diazacycloheptan (IX) umgewandelt.

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1-Methyl-3-phenyl-4-piperidone (I), when subjected to theSchmidt reaction, yielded 1-methyl-6-phenyl-1,4-diazacycloheptanone-(5) (III), the structure of which has been proved byHofmann degradation of the methiodide (V) and hydrolysis of the degradation product (VI) to give atropic acid and asym. dimethylethylenediamine. The lactam (III) has been converted into 1-methyl-6-phenyl-1,4-diazacycloheptane (IX) by means of LiAlH₄.

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Meinem verehrten Lehrer Herrn Professor Dr.H. Bretschneider zum 60. Geburtstag.     

三价银配合物氧化1,4-丁二胺的反应动力学及机理研究

碱性介质中, 在离子强度不变的条件下, 用广度法研究了三价银配合物氧化1,4-丁二胺的动力学及机理. 反应对三价银配合物和都是一级反应, 二级反应速率常数(k’) 随碱浓度的增大而增大,随糕碘酸根离子浓度的增大而减小. 据此提出了适合此反应的反应机理, 并计算得到了反应的热力学参数.     

Coordination modes of multidentate azodye ligand derived from 4,4′‐methylenedianiline towards some transition metal ions: Synthesis,spectral characterization,thermal investigation and biological activity

Nine new azodye metal complexes of Mn(II), Co(II), Ni(II), Cu(II), Cr(III), Fe(III), Ru(III), Hf(IV) and Zr(IV) ions have been prepared via the reaction of 5,5′‐((1E,1′E)‐(methylenebis(1,4‐phenylene))bis(diazene‐2,1‐diyl))bis(6‐hydroxy‐2‐thioxo‐2,3‐dihydropyrimidin‐4(5H)‐one) (H₄L) with the corresponding metal salts affording sandwich (1 L:1 M), mononuclear (2 L:1 M), binuclear (1 L,2 M) and tetranuclear (1 L,4 M) complexes. Elemental analyses, spectral methods, magnetic moment measurements and thermal studies were utilized to confirm the mode of bonding and geometrical structure for the ligand and its metal complexes. Infrared spectral data show that the H₄L ligand chelates with some metal ions in keto–enol–thione or keto–thione manner. It behaves in a neutral/dibasic tetradentate fashion in sandwich and binuclear complexes. Also, it acts as a neutral bidentate moiety in the Cr(III) complex. The spectra reveal that azo group participates in chelation in all complexes. Octahedral geometry was suggested for all chelates but the Cu(II) complex with square planar geometry. The thermal stability and decomposition of the compounds were studied, the data showing that the thermal decomposition ended with metal or metal oxide mixed with carbon as final product. The electron spin resonance spectrum of the Cu(II) complex demonstrates that the free electron is located in the ( ) orbital. Measurements of biological activity against human cell lines Hep‐G₂ and MCF‐7 reveal that the Cu(II) complex has a higher cytotoxicity in comparison to the free ligand and other metal complexes, with IC₅₀ values of 6.10 and 5.2 μg ml^?1, respectively, while the ligand has anti‐tumour activity relative to some of the investigated metal complexes.     

Fluorimetric Analysis of Aluminum in Diluted Hemodialysis Solutions by Using a Novel Schiff Base

A spectrofluorimetric method has been developed for trace amount of aluminum(III) by using a novel Schiff base, N,N′-bis(salicylidene)-1,4-diaminobuthane (BUTAS), and 4-methyl-2-aminophenol (OAP). Since the aluminum complexes are generally fluorescent, aluminum(III) increases the fluorescence intensity of BUTAS-OAP by formation of Al-BUTAS-OAP complex. The fluorescence of the complex is measured at an excitation wavelength of 410 nm with an emission at 526 nm. Aluminum(III) can be detected within a concentration limit of 0.11–1.62 ppb and the lowest detection limit being 0.07 ppb. The proposed method was applied to diluted hemodialysis solution and spectrofluorimetric data was compared with data of standard pharmacopoeia method.     

Kinetics of reduction of hydroxycuprate(III) in KOH solution

The solution of an unstable copper(III) complex, hydroxycuprate(III) i.e. Cu(OH)^– ₄, has been obtained by oxidising a copper anode in 0.5–3 M KOH solution. The kinetics of the copper(III) reduction in KOH solution has been studied spectrophotometrically and is first order with respect to copper(III), and the pseudo-first order rate constant increases as the KOH concentration increases. The kinetic data is explained by a scheme according to which a Cu^III intermediate, in equilibrium with Cu(OH)^– ₄, reacts with OH^–. On the basis of the kinetic data, the molar absorptivity of the Cu(OH)^– ₄ solution has been determined.     

Kinetics and mechanism of a macrocyclic chromium(III) complex oxidation to chromium(IV) by hexacyanoferrate(III) in strongly alkaline media

Oxidation of the macrocyclic Cr(III) complex cis-[Cr(cycb)(OH)₂]⁺, where cycb=rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, by an excess of the hexacyanoferrate(III) in basic solution, slowly produces Cr(V) species. These species, detected using e.p.r. spectroscopy, are stable under ambient conditions for many hours, and the hyperfine structure of the e.p.r. spectrum is consistent with the interaction of the d-electron with four equivalent nitrogen nuclei. Electro-spray ionization mass spectrometry suggests a concomitant oxidation of the macrocyclic ligand, in which double bonds and double bonded oxygen atoms have been introduced. By comparison basic chromate(III) solutions are oxidized rapidly to chromate(VI) by hexacyanoferrate(III) without any detectable generation of stable Cr(V) intermediates.Kinetics of oxidation of the macrocyclic Cr(III) complex in alkaline solution has been studied under excess of the reductant. Rate determining formation of Cr(IV) by a second order process involving the Cr(III) and the Fe(III) reactants is seen. This reaction also involves a characteristic higher order than linear dependence on the hydroxide concentration. Reaction mechanisms for the processes, including oxidation of the coordinated macrocyclic ligand – under excess of the oxidant- are proposed.     

Complexation and Electronic Spectra of Neodymium(III)–Amino Acid–1,10-Phenanthroline Systems in Aqueous Solution

Complexation of neodymium(III)-glutamate(glu)-phenanthroline(phen), neodymium(III)-aspartate(asp)-phenanthroline(phen) ternary systems and the corresponding binary systems in aqueous solution are discussed at various values of pH. Based on change regularity of hypersensitive transition intensities, the neodymium(III)-aspartate-phenanthroline ternary complex has a general formula of Nd(asp)₃phen, but the composition of the complex of Nd(III) with glutamate and phenanthroline is complicated and has not been determined. The electronic spectra of these complexes were studied, Slater-Condon parametersF _k ^s and the Lande parameter ξ_4f were obtained. The rms deviation between calculated and observed energy levels is less than 43 cm⁻¹. Bonding in these complexes are also investigated and bonding parameters calculated. The results show that Nd(III) and amino acids form complexes by ionic linkage with carboxylic oxygens, but with some weak covalency. Besides, the degrees of covalency in ternary complexes are larger than those in binary complexes.     

Facile C-H bond activation: synthesis of the N4C donor set pentadentate ligand 1,4-bis(2-pyridylmethyl)-1,4-diazacyclononane (dmpdacn) and a structural study of its alkyl-cobalt(III) complex [Co(dmpdacn-C)(OH2)](ClO4)2.H2O and its hydroxylated derivative [Co(dmpdacnOH-O)Cl](ClO4)2.C3H6O

The 1,4-bis(2-pyridylmethyl)-1,4-diazacyclononane (dmpdacn) ligand with a N(4)C donor set deprotonates at a CH(2) gamma to an amine under extraordinarily mild conditions (pH 7) and binds as a pentadentate ligand to Co(III) as the [Co(dmpdacn-C)(OH(2))](2+) complex. This complex was characterized by 1D and 2D NMR techniques, and a single-crystal X-ray structure is reported. In an alternative synthesis from Co(II), dmpdacn, and air, the same C-bonded complex is obtained along with a novel hydroxylated Co(III) complex [Co(dmpdacnOH-O)Cl](2+) which has been similarly characterized. Here the carbanion has been oxidized, a C- to O-bonded rearrangement has taken place, and the bound aqua group is replaced by Cl(-). The base hydrolysis kinetics of the hydroxylated Co(III) complex are reported, and mechanisms for this and the unusually facile C-H cleavage and CH(2) oxidation reactions are discussed.     

Thermal Degradation of The Poly(m-phenylene Oxadiazole) Molecules in Sulphuric Acid

Translational diffusion of poly-2,5-(1,3-phenylene)-1,3,4-oxadiazole (PMOD) in solution in 96% sulphuric acid was studied, and intrinsic viscosity was measured at different stages of thermal degradation. Polymer solution has previously been subjected to heating at temperature ranging from 75 to 104°C and then investigated at 26°C. A monotonic decrease in intrinsic viscosity and the molecular mass, M, of degraded products with increasing degradation temperature was detected. The rate constant of the degradation process has been obtained from the change in M of the degradation products with time at a fixed solution temperature, and the activation energy of the process was calculated by using the temperature dependence of the rate constant. The activation energy (E =102±8 kJ^–1 ) is close to that obtained previously for the hydrolysis of poly-2,5-(1,4-phenylene)-1,3,4-oxadiazole (PPOD) in sulphuric acid (106 kJ^–1 ), the rate constant being approximately twice in the value. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of structure on the thermal degradation and flame retardancy of hexolic anhydride based polyesters

Based on the anhydrides like hexolic (5,6,7,8,10,10-hexachloro -3a,4,4a,5,8,8a,9,9a-octahydro-5,8-methanonaphtho-[2,3-c]-furan-1,3-dione), maleic and phthalic and diols like 1,4-butanediol, cis-2-butene-1,4-diol and 2,3-dichloro-2-butene-1,4-diol, a family of polyesters has been synthesized using azeotropic condensation technique. The structural characterizations of the polyesters have been carried out using infra-red, 1^H - and ¹³C- nuclear magnetic resonance spectroscopic methods. The thermal properties of the polyesters have been studied using thermogravimetric technique. The off-line pyrolysis of these materials was done. The qualitative and semi-quantitative analyses of the volatiles as well as the heavy mass fractions of the degradation products were carried out using a gas chromatograph coupled to a mass selective detector (GC-MSD). Thermogravimetric data indicate that the thermal stability and the char residue of the polyester resins decrease in the order 1,4-butanediol based>cis-2-butene-1,4-diol based>2,3-dichloro-2-butene-1,4-diol based polyesters. The GC-MSD data indicate that the amount of flame cooling agents (hexa-, isomeric penta-, tetra- and isomeric tri-chlorocyclopentadienes) produced during the pyrolysis of the polyesters increases in the order 2,3-dichloro-2-butene-1,4-diol based<cis-2-butene-1,4-diol based<1,4-butanediol based polyesters. The trends observed in these two parameters which are contributing factors to the flame retardancy of the polyester materials were suitably explained on the basis of the effect of the structural changes in the diol part of the polyesters on the primary degradation mechanism, the β-chain scission process.     

[Cu2(C2O4)(C12H8N2)2(C3H7NO)2](ClO4)2配合物的合成及其热分解

以邻菲罗啉、2,5二羟基-1,4-二噻烷和Cu(ClO4)2.6H2O为原料,合成了中心对称的双核配合物[Cu2(C2O4)(C12H,N2)2(C3 H7NO)2](ClO4)2(1).通过红外光谱、元素分析等分析测试手段对其进行了表征;借助TG-DTG技术在氮气气氛下研究了配合物的热分解情况,并根据热分析结果确定了...