Fine-tuning the electronic properties of highly stable organometallic Cu(III) complexes containing monoanionic macrocyclic ligands

A family of highly stable organometallic Cu(III) complexes with monoanionic triazamacrocyclic ligands (L(i)) with general formula [CuL(i)]+ have been prepared and isolated, and their structural, spectroscopic, and redox properties thoroughly investigated. The HL(i) ligands have been designed in order to understand and quantify the electronic effects exerted by electron donor and electron-withdrawing groups on either the aromatic ring or the central secondary amine or on both. In the solid state the Cu(III) complexes were mainly characterized by single-crystal X-ray diffraction analysis, whereas in solution their structural characterization was mainly based on 1H NMR spectroscopy given the diamagnetic nature of the d(8) square-planar Cu(III) complexes. Cyclic voltammetry together with 1H NMR and UV/Vis spectroscopy have allowed us to quantify the electronic effects exerted by the ligands on the Cu(III) metal center. A theoretical analysis of this family of Cu(III) complexes has also been undertaken by DFT calculations to gain a deeper insight into the electronic structure of these complexes, which has in turn allowed a greater understanding of the nature of the UV/Vis transitions as well as the molecular orbitals involved.     

Electrocatalytic O2 reduction by covalently immobilized mononuclear copper(I) complexes: evidence for a binuclear Cu2O2 intermediate

A Cu(I) complex of 3-ethynyl-phenanthroline covalently immobilized onto an azide-modified glassy carbon surface is an active electrocatalyst for the four-electron (4-e) reduction of O(2) to H(2)O. The rate of O(2) reduction is second-order in Cu coverage at moderate overpotential, suggesting that two Cu(I) species are necessary for efficient 4-e reduction of O(2). Mechanisms for O(2) reduction are proposed that are consistent with the observations for this covalently immobilized system and previously reported results for a similar physisorbed Cu(I) system.     

Bis(μ-oxo) dicopper(III) species of the simplest peralkylated diamine: enhanced reactivity toward exogenous substrates

N,N,N',N'-tetramethylethylenediamine (TMED), the simplest and most extensively used peralkylated diamine ligand, is conspicuously absent from those known to form a bis(μ-oxo)dicopper(III) (O) species, [(TMED)(2)Cu(III)(2)(μ(2)-O)(2)](2+), upon oxygenation of its Cu(I) complex. Presented here is the characterization of this O species and its reactivity toward exogenous substrates. Its formation is complicated both by the instability of the [(TMED)Cu(I)](1+) precursor and by competitive formation of a presumed mixed-valent trinuclear [(TMED)(3)Cu(III)Cu(II)(2)(μ(3)-O)(2)](3+) (T) species. Under most reaction conditions, the T species dominates, yet, the O species can be formed preferentially (>80%) upon oxygenation of acetone solutions, if the copper concentration is low (<2 mM) and [(TMED)Cu(I)](1+) is prepared immediately before use. The experimental data of this simplest O species provide a benchmark by which to evaluate density functional theory (DFT) computational methods for geometry optimization and spectroscopic predictions. The enhanced thermal stability of [(TMED)(2)Cu(III)(2)(μ(2)-O)(2)](2+) and its limited steric demands compared to other O species allows more efficient oxidation of exogenous substrates, including benzyl alcohol to benzaldehyde (80% yield), highlighting the importance of ligand structure to not only enhance the oxidant stability but also maintain accessibility to the nascent metal/O(2) oxidant.     

Differentiation of Streptococcus mutans serotypes by discriminant analysis of pyrolysis—gas—liquid chromatography data

Curie-point pyrolysis with a relatively low resolution gas—liquid chromatographic system (packed Carbowax 20M columns) provided data on washed cells of oral streptococci. When the data were ordered into a hierarchy of comparisons the steps were matched not only by the increase in variability between sets but also by the proportion of the output showing relatively high variability. It was possible to segregate strains of Streptococcus mutans serotype c from those of different serotypes by use of a discriminant function derived from only three pyrogram peaks.     

Simple iron catalyst for terminal alkene epoxidation

[reaction: see text] A mu-oxo-iron(III) dimer, [((phen)(2)(H(2)O)Fe(III))(2)(mu-O)](ClO(4))(4), is an efficient epoxidation catalyst for a wide range of alkenes, including terminal alkenes, using peracetic acid as the oxidant. Low catalyst loadings, in situ catalyst preparation from common reagents, fast reaction times (<5 min at 0 degrees C), and enhanced reaction performance at high substrate concentrations combine to create a temporally and synthetically efficient procedure for alkene epoxidation.     

New99mTc-diiodine substituted IDA derivative (DIIODIDA) for hepatobiliary imaging

A new diiodine substituted IDA derivative, 2,4-diiodine-6-methyl IDA (DIIODIDA) was synthesized and labeled with^99mTc. It was established that^99mTc-DIIODIDA had high radiochemical purity. Biodistribution and influence of bilirubin on^99mTc-DIIODIDA biokinetics has been studied in rats and compared to the corresponding results for^99mTc-SOLCOIODIDA. Related to^99mTc-SOLCOIODIDA,^99mTc-DIIODIDA has much better biliary exretion (55.18 versus 43.63%). No change of^99mTc-DIIODIDA biokinetics, under influence of bilirubin was noticed. Biliary excretion of^99mTc-SOLCOIODIDA has been reduced for about 60%. The protein binding of^99mTc-DIIODIDA and^99mTc-SOLCOIODIDA were also determined, using in vitro method of precipitation. These results showed that^99mTc-DIIODIDA hepatobiliary imaging agent is superior to the presently used^99mTc-monoiodine IDA derivatives.     

Factors influencing the ultrasonic separation of oil-in-water emulsions

Ultrasound may have inherent shortcomings that preclude its ability to coagulate grease from wastewater, yet these may be overcome by the simultaneous application of electrolysis. We studied the role of pH, conductivity, temperature, ultrasound intensity and duration, and electrolysis voltage, current, and duration, in the study treatment. Conductivity was found to be the most significant factor, however interactions among the eight study variables are likely more important than individual factors. The proposed process was capable of removing up to 100% of grease from the studied wastewater.