Gerald S. Vigee

The synthesis of binuclear copper(II) complexes and the study of their catecholase activity

Abstract Three new binuclear copper(II) complexes have been prepared with shift bases derived from the condensation of 2,6-diformyl-4-methylphenol with the amino acids lysine, glutamic acid and arginine. The binuclearity of the complexes was characterized from optical, magnetic and electron spin resonance studies. Their ability to catalyze the dioxygen oxidation of several substituted catechols was measured using oxygen uptake and optical techniques.

The interaction of substituted catechols with some binuclear copper(II) compounds

Four dicopper(II) complexes were tested as catalysts for the air oxidation of several substituted o-diphenols. The oxidation reactions were followed by measuring the change in the optical spectra and by measuring the oxygen uptake. The oxidase activities decreased with a decrease in pH and increased for o-diphenols with good electron donating substituents in the para position. Because of their complexity, the oxidation products were not identified and characterized. Lack of characterized products prevented an analysis of the reaction mechanism.

The line broadening and contact shift studies of some metal ion-DMSO complexes

Abstract Contact shift and line broadening studies were made on a series of metal ion-dimethylsulfoxide (DMSO) solutions. Unpaired spin density transfer for Cu(DMSO)62+ and Ni (DMSO)62+ complexes is through the σ bonding system while the signs of the electron spin-nuclear spin coupling constants, An, for Co(DMSO)62+, Fe(DMSO)62+ indicate a ligand π-to-metal t2g unpaired spin density transfer. Line broadening studies reveal that Co(DMSO)62+ and Mn(DMSO)62+ exchange too fast in DMSO solution to be measured by the NMR technique while Fe(DMSO)63+ and Cr(DMSO)63+ exchange too slowly to be measured. The exchange rate and the ΔH‡ and ΔS‡ of exchange were determined for Cu(DMSO)62+, Ni(DMSO)62+ and Fe(DMSO)62+. The exchange rate order was found to be Fe > Cu > Ni.

The chemical dynamics of 1,4,8,11-tetraazacyclotetradecane nickel(II) perchlorate with several solvents. I. Thermodynamics of base adduct formation

Abstract A solvent adduct study of 1,4,8,11-tetraazacyclotetradecane nickel(II) perchlorate with the coordinating solvents acetonitrile, N,N-dimethylformamide (DMF), methyl sulfoxide (DMSO), and water by optical and nmr techniques is reported. The thermodynamic parameters ΔH°, ΔS°, and K eq for adduct formation are given for each solvent system. At 25 °C, the stability order is found to be DMF > CH 3 CN > DMSO > H 2 O. A comparison of the observed stability order and stabilities predicted by single optical measurements and solvent donicity is presented.

Copper complexes which catalyze the air oxidation of 4-methyl catechol

Abstract A study of the air oxidation of 4-methyl catechol catalyzed by simple copper-amine complexes was performed in aqueous solutions at pH = 6.5. Simple bi-, tri- and tetra-nitrogen ligands were complexed to Cu 2+ ions. Initial rate kinetics of their catalytic oxidation of 4-methyl catechol was followed optically. Proton NMR linebroadening and optical spectral studies were performed on the Cu 2+ -amine-catechol solutions and these spectral data were correlated with the kinetic studies.

Synthesis and study of isomers of bis(4-aminosalicylato)copper(II)

Abstract Synthesis of bis(4-aminosalicylato)copper(II) from 4-aminosalicylic acid yields two isomers of the complex that have different physical characteristics, but similar chemical properties. Characterization of the isomers indicates that both are monomeric with coordination to the metal ion occuring through the carbonyl oxygens of the ligand. Both complexes are essentially square planar with normal magnetic moments. Both isomers are thermally stable in the solid state and are insoluble in common solvents. The isomer produced during synthesis is determined by the concentration of reactants.

Dicopper complexes of polyethyleneimine and polyvinylamine vinylsulfonate

Abstract Binuclear copper(II) complexes prepared with the binucleating ligand 2,6-diformyl-4-methyl-phenol were attached as pendant groups to the polymers polyethyleneimine and polyvinylaminevinyl sulfonate sodium salt. The polymer-copper(II) complexes were characterized from optical and magnetic studies and their catecholase activities were measured in water. Polyvinylamine-vinylsulfonate-copper(II) is insoluble in water and showed little if any catecholase activity. The polyethyleneimine-copper complexes were reasonably soluble in water and demonstrated good catecholase activity. The catecholase activity of the polyethyleneimine-copper complexes increased in activity with an increase in the ratio of polymer-to-copper content (based on a constant copper concentration).

An investigation of the stereochemistry of some nickel(II) tetraamines in acetonitrile solution

Abstract The equilibria of adduct formation between several nickel(II) tetraamine complexes and acetonitrile were determined from −40 to 80 °C in acetonitrile solution by the Evans NMR magnetic susceptibility method. The stability order for adduct formation of the paramagnetic complex in terms of the ligand was found to be: 2,2,2-tet, 3,3,3-tet > 3,2,3- tet > 2,3,2-tet > cyclam. This order parallels that found in previous studies in aqueous solution. However, in this study, enthalpic factors were found to be dominant whereas enthalpic and entropic factors have been reported to be comparable in magnitude in aqueous solution. Optical studies from 200–1500 nm were conducted on 0.01 M acetonitrile solutions of the complexes from 25–65 °C. Only small changes in the intensity and position of the optical bands were observed with temperature except for the 2,3,2-tet (468 nm), 3,2,3-tet (450 nm), and cyclam (460 nm) complexes. These indicated bands increase with increasing temperature, which can be explained by assuming a square-planar (diamagnetic)-octahedral (paramagnetic) equilibrium in agreement with the magnetic susceptibility data. Band assignments were made for the cis- and trans -octahedral isomers for each of the complexes. The order of cis -octahedral character for the complexes was found to be 2,2,2- tet, 3,3,3-tet > 2,3,2-tet > 3,2,3-tet > cyclam in agreement with previous studies in aqueous, DMSO, and DMF solutions.

The chemical dynamics of base adducts with bis(N,N-dithiocarbamate)nickel(II)

The chemical dynamics for the adduct reactions of the nitrogen bases pyridine, 2-picoline, 3-picoline, 4-picoline and 3,5-lutidine with bis(N,N-dialkyldithiocarbamate)nickel(II) were investigated. The thermodynamic parameters for adduct formation were determined by NMR techniques. The pyridine-Ni(diR,R′dtc)2 adducts have the stability order -CH2H5 < -n-C3H7 < -n-C4H9; the order is controlled by entropy rather than by enthalpy effects contrary to previously reported results from i.r. and vis spectral studies. At low temperatures the adduct stability order of Ni-(din-butyldtc)2 with pyridine type bases is 3,5-lutidine < 3-picoline < 4-picoline < pyridine. However, at 25°C the order changes to pyridine ∼3-picoline ∼3,5-lutidine < 4-picoline, the change in stability order with temperature being attributed to the T Δ S° term. The kinetic parameters ΔH≠, and ΔS≠ for 3-picoline and 4-picoline exchange with Ni(din-butyldtc)2 were determined by NMR line broadening techniques. The rate constants, κ≠, were found to be 12·5 × 104 sec−1 for 3-picoline and 6·2 × 104 sec−1 for 4-picoline. Temperature studies of contact shifts and INDO molecular orbital calculations are used to analyze the unpaired spin density transfer between the Ni(din-butyldtc)2 and the pyridine type bases.

Dicopper complexes as oxidase catalysts immobilized on polystyrene and polyacrylic beads

Abstract The simple dicopper(II) complexes FSAL(Glu) 2 Cu 2 OH·2H 2 O and FSAL(Lys) 2 Cu 2 ·2HCl·2H 2 O, previously used as oxidase catalysts, were anchored to polystyrene and oxirane acrylic beads. The ability of the immobilized dicopper-bead complexes to catalyze the oxidation of catechol was measured and their catalytic activities were compared with those of the simple dicopper complexes used as homogeneous catalysts. The catecholase activities of the dicopper bead complexes, although found to be reasonably high, were less than the activities of the simple dicopper complexes.