Complex Formation Tendency Research Articles

Conductometric and viscometric investigation of poly(N‐vinylimidazole)‐metal ion complex formation

AbstractThe complexation of copper (Cu2+), cobalt (Co2+), and cadmium (Cd2+) ions with poly(N‐vinylimidazole) (PVIm) and its protonated form in aqueous solution was studied conductometrically and viscometrically. From the conductometric and viscometric curves, it was found that four imidazole units were coordinated with one metal ion in the complex systems. Both studies showed that the complex formation tendency decreased in the following order: Cu2+ > Co2+ > Cd2+. Complex properties of metal ions with imidazole group were explained by referring to Pearson's treatment, as hard and soft acids and bases. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 376–384, 2002

Dipole Moment Studies of n-butanol, i-butanol and t-butanol with Chlorobenzene Complexes

The dipole moments of H-bonded complexes of n-butanol, i-butanol and t-butanol with chlorobenzene in benzene were investigated from dielectric measurements at 455 kHz and at temperature 303.16 K. The dipole moment of the complex (μab), interaction dipole moment (Δμ) and induced polarization (Pab) for thermodynamically most favoured geometry of 1:1 complexes in these systems were determined. The results shows that the complexation is due to charge redistribution effect in all cases studied and the tendency of complex formation is maximum in n-butanol system.

Chemical and functional characterization of metal-binding pseudotripeptides with different functionalized N-alkyl residues

Pseudotripeptide ligands with 4 different N-functionalized glycine residues were qualitatively, semiquantitatively and quantitatively tested for their complexation of the bivalent transition metal ions Zn2+, Cu2+, Co2+, Ni2+ and Mn2+. The functional side chains have different length and different groups available for complexation. MALDI-MS and ESI-MS were used for more qualitative or semiquantitative estimation of the complex formation tendencies. The found ranking differs by these two methods only for Zn2+ and Ni2+. For one of the pseudotripeptide ligands, the ligand L1, complex formation with certain transition metal was estimated quantitatively by potentiometric titration. The Zn-complex of that ligand polarizes bound water strongly, resulting in a low pK a -value. Complexes of pseudotripeptide ligand L1 with certain metal ions were tested for their hydrolytic activity. The pseudo first order rate constants of the hydrolysis of the substrates 4-nitrophenyl acetate and bis(4-nitrophenyl)phosphate were compared to complexes with the same metal ions formed with a very well studied ligand from the literature, the 1,4,7,10-tetraaza cyclododecane (cyclen). The hydrolysis of the phosphate ester occurs very slowly compared to the acetate ester. No correlation exists between the estimated pK a values of complexes formed from ligand L1 with different metal ions and the phosphate ester hydrolysis. The Ni ions give totally different hydrolytic activities for pseudotripeptide ligand L1 and cyclen. With one exception, the Ni-cyclen complex, all other complexes have only a low or moderate catalytic activity.

Chemical and functional characterization of metal-binding pseudotripeptides with different functionalized N-alkyl residues Dedicated to Professor Dr. Ernst-Gottfried Jaeger on occasion of his 65th birthday

Pseudotripeptide ligands with 4 different N-functionalized glycine residues were qualitatively, semiquantitatively and quantitatively tested for their complexation of the bivalent transition metal ions Zn2+, Cu2+, Co2+, Ni2+ and Mn2+. The functional side chains have different length and different groups available for complexation. MALDI-MS and ESI-MS were used for more qualitative or semiquantitative estimation of the complex formation tendencies. The found ranking differs by these two methods only for Zn2+ and Ni2+. For one of the pseudotripeptide ligands, the ligand L1, complex formation with certain transition metal was estimated quantitatively by potentiometric titration. The Zn-complex of that ligand polarizes bound water strongly, resulting in a low pKa-value. Complexes of pseudotripeptide ligand L1 with certain metal ions were tested for their hydrolytic activity. The pseudo first order rate constants of the hydrolysis of the substrates 4-nitrophenyl acetate and bis(4-nitrophenyl)phosphate were compared to complexes with the same metal ions formed with a very well studied ligand from the literature, the 1,4,7,10-tetraaza cyclododecane (cyclen). The hydrolysis of the phosphate ester occurs very slowly compared to the acetate ester. No correlation exists between the estimated pKa values of complexes formed from ligand L1 with different metal ions and the phosphate ester hydrolysis. The Ni ions give totally different hydrolytic activities for pseudotripeptide ligand L1 and cyclen. With one exception, the Ni-cyclen complex, all other complexes have only a low or moderate catalytic activity.

Complex-radical Alternating Copolymerization oftrans-Stilbene withN-Substituted Maleimides

Radical copolymerization of donor-acceptor monomers, i.e. transstilbene (Stb) with N-maleimide (MI), N-ethylmaleimide (EtMI) and N-phenylmaleimide (PhMI), are studied. Constants of charge-transfer complex formation (K c ) and copolymerization (r 1 and r 2 ) are determined by HannaAshbaugh ( 1 H nuclear magnetic resonance) and Kelen-Tudos methods, respectively. The results obtained were analysed by use of the complex copolymerization model of Seiner-Litt. It is found that the tendency for complex formation and the tendency for alternation of monomers depend on the nature of the N-substituent in the maleimide molecule. K c is found to increase in the order EtMI EtMI > PhMI. It is shown by thermogravimetric analysis, differential thermal analysis and differential scanning calorimetry that the alternating copolymers synthesized have high thermostabilities. The copolymers synthesized show increased thermal stabilities, as well as glass transition temperatures, with the change of imide N-substituent. Stb-MI, Stb-EtMI and Stb-PhMI copolymers decompose through a one-step reaction at 456, 460 and 468°C, respectively.

Complexradical Alternating Copolymerization of trans-Stilbene with N-Substituted Maleimides

Radical copolymerization of donor–acceptor monomers, i.e. trans-stilbene (Stb) with N-maleimide (MI), N-ethylmaleimide (EtMI) and N-phenylmaleimide (PhMI), are studied. Constants of charge-transfer complex formation (Kc) and copolymerization (r1 and r2) are determined by Hanna–Ashbaugh (1H nuclear magnetic resonance) and Kelen–Tüdöş methods, respectively. The results obtained were analysed by use of the complex copolymerization model of Seiner–Litt. It is found that the tendency for complex formation and the tendency for alternation of monomers depend on the nature of the N-substituent in the maleimide molecule. Kc is found to increase in the order EtMI < MI < PhMI, and the tendency for alternation (r1 · r2) decreases in the order MI > EtMI > PhMI. It is shown by thermogravimetric analysis, differential thermal analysis and differential scanning calorimetry that the alternating copolymers synthesized have high thermostabilities. The copolymers synthesized show increased thermal stabilities, as well as glass transition temperatures, with the change of imide N-substituent. Stb–MI, Stb–EtMI and Stb–PhMI copolymers decompose through a one-step reaction at 456, 460 and 468°C, respectively.

Dielectric Studies of Hydrogen Bonded Complexes Tri-n-Butyl Phosphate (TBP) with Long-Chain Aliphatic Alcohols

The mechanism of dipolar complexation involving TBP and three long chain aliphatic alcohols namely 1-hexanol, 1-heptanol, 1-octanol in a non-polor medium (benzene) was investigated from dielectric measurements at frequency 455 kHz and at temperature 303.16 K using modified Palit's method. The dipole moment of the complex (µ b c ), interaction dipole moment (Δµ), dipole moment of the H-bonded bridge (µ * ) and induced polarization (Δ P ) for the thermodynamically most favoured geometry of 1:1 complexes of these systems were computed. The results shows that complexation is due to partial proton transfer in all the cases studied and the tendency of complex formation is maximum in 1-heptanol system.

Komplexe von Acetylaceton und Acetonylaceton mit Alkali- und Erdalkaliionen. MO-SCF-Berechnungen und UV-Spektroskopie

In analogy to previous investigations on main group metal ion complexes with diacetyl2, model calculations within the LCGO MO SCF framework using minimal basis sets are used in combination with UV spectrocopy in order to investigate complex formation tendencies, eventual ion specifities and ion binding energies of Li, Na, K, Mg and Ca ions with dicarbonyl ligands. The influence of the separation of the coordinative centers by methylene groups on the interaction with these metal ions is discussed. The simple quantum chemical models seem to work in the case of diacetyl and acetylacetone, whereas they fail in the prediction of the experimentally observed interaction of acetonylacetone with the metal ions.

The complex formation of biuret with alkali and alkaline earth metal ions. NMR and solubility studies

The formation of complexes between biuret and the ions of Li, Na, K, Rb and Be, Mg, Ca, Sr and Ba in DMSO solutions hase been studied by means of 1H NMR spectrocopy. Equilibrium constants have been evaluated from the concentration dependence of NMR shifts. The results of these investigations have been supplemented by studies on changes of salt solubilities in DMSO upon addition of biuret. The complex formation tendency is compared with stabilization from HF--SCF--MO calculations.

A kinetic study of the seeded growth of barium sulfate in the presence of additives

The crystallization of barium sulfate seed crystals in supersaturated solutions has been studied conductometrically and radiochemically at 25°C. After an initial surge reflecting secondary nucleation, the crystal growth follows a rate law second-order in relative supersaturation, both in the absence and presence of additives. Organic polyphosphonates and polymeric molecules such as polygalacturonic acid and ethylenemaleic anhydride co-polymer are effective inhibitors of crystallization. The inhibiting influence of benzene polycarboxylic acids can be related to the tendency for complex formation with barium ions and to the pH of the supersaturated solutions.

Oxidation of Substituted Glycollic Acids by Ce(IV) in Sulphuric Acid Solutions

Abstract A comparison of the rate constants, dissociation constants, tendency of complex formation and catalytic activity of Mn(II) in the oxidation of substituted glycollic acids (benzilic, Dl-atrolactic, 2-hydroxyisobutyric, p-chloromandelic, p-bromomandelic, mandelic and lactic acids) by Ce(IV) in sulphuric acid solutions has been made. Hydrolyzed species of Ce(IV) are reactive and the kinetics conform to the empirical rate law -\fracd[Ce(IV)]dt=\frackK[Ce(IV)][Org. Acid][HSO_4^-]^2([H^+]+K[Org. Acid]) The reactivity and the chelating tendency of the acids seem to follow the substituent order, C6H5&amp;gt; CH3&amp;gt;H. The catalytic activity of Mn(II) appears to follow the same order as in the oxidation of these acids by Mn(III).

Interaction entre pigments et acides nucleiques Etude sur l'interaction de l'Actinomycine D avec les nucléosides par Dichroïsme Circulaire

The interaction of Actinomycin C 1 (AM) with purine nucleosides was investigated by circular dichroism. While dG and dGMP show identical interactions, rG, rGMP and 8-aza-GMP show lower tendency for complex formation. ara-G shows no complex formation. 6-Thio-GMP shows the strongest affinity for AM in accordance with previous results. Substitution on N-7 (methylation, protonation) or C-8 (8-Br-rG, 8-SH-rG) eliminate completely the complexing capacity. Another type of weaker complexes is formed by dA, dAMP and rIMP, indicated by the appearance of a positive band at 440 nm. It is concluded that in these complexes both the electron donor capacity of the purine base as well as the steric flexibility of the sugar around the glycosidic linkage determine their complexing capacity.

Etherate formation in organoaluminum compounds. Complex-formation tendency in a series of trialkylaluminum, dialkylaluminum chloride, alkylaluminum dichloride, and aluminum chloride aryl etherates

Etherate formation in organoaluminum compounds. Complex-formation tendency in a series of trialkylaluminum, dialkylaluminum chloride, alkylaluminum dichloride, and aluminum chloride aryl etherates

Studies at coordination compounds of uranyl acetate with some organic compounds. The system: Uranyl acetate–resorcinol–water

AbstractIn a previous communication on the studies of complexes of uranyl acetate with catechol, the formation of complexes at (1:1) and (1:2) molar ratios has been reported. Dihydroxyphenols, in general, have been found to show a strong tendency towards complex formation. Resorcinol which has the phenolic groups in the meta position may also, therefore, show tendency for complex formation with uranium, although to a lesser degree than that of catechol.

An examination of the basic nature of the trihalides of phosphorus, arsenic and antimony

Literature reports of the complexes, PCl 3BF 3 and PCl 3BCl 3, were investigated by conducting vapour pressure-composition measurements on the systems at low temperatures. Large, positive deviations from ideal liquid behaviour were observed in both cases, indicating no tendency for complex formation. An examination of the properties of POCl 3BCl 3 indicates the complexes reported in the literature to be phosphorus oxychloride-boron trihalide addition compounds. The 1 : 1 addition complexes of boron tribromide with phosphorus trichloride and tribromide were prepared, thus confirming the existence of these complexes. The PCl 3BBr 3 complex was noted to exchange on standing. The AsCl 3BCl 3 system was studied and found to be analogous to the PCl 3BF 3 system. Examination of the PCl 3Al 2Cl 6, PCl 3Ga 2Cl 6, AsCl 3Al 2Cl 6, AsCl 3Ga 2 Cl 6, SbCl 3BCl 3, AsBr 3BBr 3 and SbBr 3BBr 3, systems failed to give any evidence for the formation of stable complexes. Thus, of the halides studied only phosphorus trichloride and tribromide exhibited basic tendencies. The donor tendencies of the trihalides of phosphorus are discussed.