Stepwise incorporation of copper(II) into a double-ring octaaza macrocycle and consecutive oxidation to the trivalent state

The double-ring octaaza macrocycle bisdioxocyclam (I) was prepd. by the single-step aminolytic condensation of the appropriate tetraester and linear tetraamine in 1:2 molar ratio. The complexation of Cu(II) by I in aq. soln. was studied by potentiometry. Monometallic and dimetallic complex species form according to the ligand:metal ratio. In general, incorporation of Cu(II) ion into each tetraaza subunit promotes a simultaneous deprotonation of the 2 amido groups. The log k values of complexation equil. are compared with those for the ref. single-ring tetraaza macrocycle dioxocyclam. The [CuII2(bisdioxocyclamato(4-))] complex undergoes a reversible oxidn. to the dicopper(III) complex through 2 consecutive 1-electron steps, whose electrode potentials are sepd. by 110 mV

Electron transfer across the interface gold/self-assembled organic monolayer : comparison of single- and two-component systems

Single- and two-component self-assembled organic monolayers (SAM) formed of HS-C 10H 20- COOH and the HS-C 10H 20-COOH + HS-C 6H 12-OH mixture and applied on gold electrodes of different shapes and roughness are studied. The resulting monolayers are characterized in 1 M NaNO 3 solutions by the methods of electrochemical impedance spectroscopy in the frequency range from 1 Hz to 100 kHz and cyclic voltammetry in the potential range from 0 to -0.4 V (SCE). Using these method, the behavior of modified single-crystal and polycrystalline gold electrodes in electrolyte solutions of different acidity is assessed and the standard rate constants for the Ru[(NH 3) 6] 3+/2+ redox reaction are determined. The SAM film formed from the ethanol solution of the HS-C 10H 20-COOH + HS-C 6H 12-OH mixture (0.025 M) on the Au(210) single-crystal face lowers down the rate of the heterogeneous Ru[(NH 3) 6] 3+/2+ reaction from 1.5 to 4.02 7 10 -4 cm/s in the electrolyte solution with pH from 2. In solutions with higher pH, the rate constant is higher by almost an order of magnitude (2.74 7 10 -3 cm/s). The distribution of micropores in SAM films is studied within the framework of a model of micro-array electrodes. The results of studies are compared with the literature data on the gold electrode in solutions of inactive electrolytes in the absence and in the presence of SAM films formed by alkylmercaptans with equal chain lengths

Microwave-assisted chemical-free hydrolysis of wool keratin

Wool fibers were submitted to "green hydrolysis" with superheated water in a microwave reactor, in view of the potential exploitation of keratin-based industrial and stock-farming wastes. The liquid fraction was separated by filtration from the solid fraction, which consists mainly of small fragments of wool fibers and other insoluble protein aggregates. The liquid fraction contains free amino acids, peptides and low molecular weight proteins, with a small amount of cystine and lanthionine, and has a different secondary structure when compared with keratins extracted from wool via reductive or oxidative methods. Cleavage of the cystine disulfide bonds without the use of harmful, often toxic, reductive or oxidative agents allows the extraction of protein material from keratin wastes, offering the possibility of larger exploitation and valorization