Catalytic oxidation of cyclohexane with hydrogen peroxide and a tetracopper(II) complex in an ionic liquid

The catalytic peroxidative oxidation (with H2O2) of cyclohexane in an ionic liquid (IL) using the tetracopper(II) complex [(CuL)2(μ4-O,O′,O′′,O′′′-CDC)]2·2H2O [HL = 2-(2-pyridylmethyleneamino)benzenesulfonic acid, CDC = cyclohexane-1,4-dicarboxylate] as a catalyst is reported. Significant improvements on the catalytic performance, in terms of product yield (up to 36%), TON (up to 529), reaction time, selectivity towards cyclohexanone and easy recycling (negligible loss in activity after three consecutive runs), are observed using 1-butyl-3-methylimidazolium hexafluorophosphate as the chosen IL instead of a molecular organic solvent including the commonly used acetonitrile. The catalytic behaviors in the IL and in different molecular solvents are discussed.

Solvent-free microwave-assisted peroxidative oxidation of alcohols catalyzed by Iron(III)-TEMPO catalytic systems

The iron(III) complexes [H(EtOH)][FeCl2(L)(2)] (1), [H(2)bipy](1/2)[FeCl2(L)(2)].DMF (2) and [FeCl2(L)(2,2'-bipy)] (3) (L = 3-amino-2-pyrazinecarboxylate; H(2)bipy = doubly protonated 4,4'-bipyridine; 2,2'-bipy = 2,2'-bipyridine, DMF = dimethylformamide) have been synthesized and fully characterized by IR, elemental and single-crystal X-ray diffraction analyses, as well as by electrochemical methods. Complexes 1 and 2 have similar mononuclear structures containing different guest molecules (protonated ethanol for 1 and doubly protonated 4,4'-bipyridine for 2) in their lattices, whereas the complex 3 has one 3-amino-2-pyrazinecarboxylate and a 2,2'-bipyridine ligand. They show a high catalytic activity for the low power (10 W) solvent-free microwave assisted peroxidative oxidation of 1-phenylethanol, leading, in the presence of TEMPO, to quantitative yields of acetophenone [TOFs up to 8.1 x 10(3) h(-1), (3)] after 1 h. Moreover, the catalysts are of easy recovery and reused, at least for four consecutive cycles, maintaining 83 % of the initial activity and concomitant rather high selectivity. 3-Amino-2-pyrazinecarboxylic acid is used to synthesize three new iron(III) complexes which act as heterogeneous catalysts for the solvent-free microwave-assisted peroxidative oxidation of 1-phenylethanol.

Y Trinuclear Cu-II structural isomers coordination, magnetism, electrochemistry and catalytic activity towards the oxidation of alkanes

The reaction of the Schiff base (3,5-di-tert-butyl-2-hydroxybenzylidene)-2-hydroxybenzohydrazide (H3L) with copper(II) nitrate, acetate or metaborate has led to the isomeric complexes [Cu-3(L)(2)(MeOH)(4)] (1), [Cu-3(L)(2)(MeOH)(2)]2MeOH (2) and [Cu-3(L)(2)(MeOH)(4)] (3), respectively, in which the ligand L exhibits dianionic (HL2-, in 1) or trianionic (L3-, in 2 and 3) pentadentate 1O,O,N:2N,O chelation modes. Complexes 1-3 were characterized by elemental analysis, IR spectroscopy, single-crystal X-ray crystallography, electrochemical methods and variable-temperature magnetic susceptibility measurements, which indicated that the intratrimer antiferromagnetic coupling is strong in the three complexes and that there exists very weak ferromagnetic intermolecular interactions in 1 but weak antiferromagnetic intermolecular interactions in both 2 and 3. Electrochemical experiments showed that in complexes 1-3 the Cu-II ions can be reduced, in distinct steps, to Cu-I and Cu-0. All the complexes act as efficient catalyst precursors under mild conditions for the peroxidative oxidation of cyclohexane to cyclohexyl hydroperoxide, cyclohexanol and cyclohexanone, leading to overall yields (based on the alkane) of up to 31% (TON = 1.55x10(3)) after 6 h in the presence of pyrazinecarboxylic acid.

Research progress on reuse of fluid catalytic cracking waste from oil refinery in cement-based materials

Present paper present the main results obtained in the scope of an ongoing project which aims to contribute to the valorization of a waste generated by the Portuguese oil company in construction materials. This waste is an aluminosilicate with high pozzolanic reactivity. Several different technological applications had already been tested with success both in terms of properties and compliance with the corresponding standards specifications. Namely, this project results already demonstrated that this waste can be used in traditional concrete, self-compacted concrete, mortars (renders, masonry mortar, concrete repair mortars), cement main constituent as well as alkali activated binders.

Arylhydrazones of barbituric acid: synthesis, coordination ability and catalytic activity of their CoII, CoII/IIIand CuIIcomplexes toward peroxidative oxidation of alkanes

New ortho-substituted arylhydrazones of barbituric acid, 5-(2-(2-hydroxyphenyl)hydrazono) pyrimidine-2,4,6(1H,3H,5H)-trione (H4L1) and the sodium salt of 2-(2-(2,4,6-trioxotetra-hydropyrimidin-5(2H)-ylidene)hydrazinyl) benzenesulfonic acid (H4L2), [Na(H3L2)(mu-H2O)(H2O)(2)](2) (1), were used in the synthesis of Cu-II, Co-II and Co-II/III complexes, [Cu(H2L1)(H2O)(im)]center dot 3H(2)O (im = imidazole) (2), [Co(H2O)(6)] [Co(H2L1)(2)](2)center dot 8H(2)O (3), [Co(H2L2)(im)(3)] (4), [Cu(H2L2)(im)(2)]center dot H2O (5) and [Co(H2O)(6)][H3L2](2)center dot 8H(2)O (6). The complexes are water soluble and the mono-or di-deprotonated ligands display different coordination modes, depending on the synthetic conditions. The electrochemical behaviour of all the compounds was investigated by cyclic voltammetry and controlled potential electrolysis, revealing that the ligands are also redox active. All the compounds were evaluated as catalysts for the peroxidative (with H2O2) oxidation of cyclohexane at room temperature. The compounds 2 and 3 are the most active ones (yields up to 21% and TON up to 213 are achieved, in the presence of 3).

Novel coordination polymers with (Pyrazolato)-based tectons: catalytic activity in the peroxidative oxidation of alcohols and cyclohexane

Coupling five rigid or flexible bis(pyrazolato)based tectons with late transition metal ions allowed us to isolate 18 coordination polymers (CPs). As assessed by thermal analysis, all of them possess a remarkable thermal stability, their decomposition temperatures lying in the range of 340-500 degrees C. As demonstrated by N-2 adsorption measurements at 77 K, their Langmuir specific surface areas span the rather vast range of 135-1758 m(2)/g, in agreement with the porous or dense polymeric architectures retrieved by powder X-ray diffraction structure solution methods. Two representative families of CPs, built up with either rigid or flexible spacers, were tested as catalysts in (0 the microwave-assisted solvent-free peroxidative oxidation of alcohols by t-BuOOH, and (ii) the peroxidative oxidation of cydohexane to cydohexanol and cydohexanone by H2O2 in acetonitrile. Those CPs bearing the rigid spacer, concurrently possessing higher specific surface areas, are more active than the corresponding ones with the flexible spacer. Moreover, the two copper(I)-containing CPs investigated exhibit the highest efficiency in both reactions, leading selectively to a maximum product yield of 92% (and TON up to 1.5 x 10(3)) in the oxidation of 1-phenylethanol and of 11% in the oxidation of cydohexane, the latter value being higher than that granted by the current industrial process.

Catalytic oxidation of alcohols: recent advances

This review concerns metal-catalyzed reactions of oxidation of alcohols to the respective products, mainly ketones and aldehydes, mostly within the period of 2010–2014. Both conventional and unconventional systems, not only with usual reagents, but also with uncommon and prospective ones, are overviewed, with recently achieved developments.

Screening pentachlorophenol degradation ability by environmental fungal strains belonging to the phyla Ascomycota and Zygomycota

Pentachlorophenol (PCP) bioremediation by the fungal strains amongst the cork- colonising community has not yet been analysed. In this paper, the co- and direct metabolism of PCP by each of the 17 fungal species selected from this community were studied. Using hierarchical data analysis, the isolates were ranked by their PCP bioremediation potential. Fifteen isolates were able to degrade PCP under co-metabolic conditions, and surprisingly Chrysonilia sitophila, Trichoderma longibrachiatum, Mucor plumbeus, Penicillium janczewskii and P. glandicola were able to directly metabolise PCP, leading to its complete depletion from media. PCP degradation intermediates are preliminarily discussed. Data emphasise the signiWcance of these fungi to have an interesting potential to be used in PCP bioremediation processes.

Oxo-molybdenum(VI) complexes containing chiral ligands: catalytic applications in selective epoxidations

Dissertation presented to obtain the Ph.D. degree in Chemistry

Voltammetric analysis of mancozeb and its degradation product ethylenethiourea

The purpose of this work was to develop a reliable alternative method for the determination of the dithiocarbamate pesticide mancozeb (MCZ) in formulations. Furthermore, a method for the analysis of MCZ's major degradation product, ethylenethiourea (ETU), was also proposed. Cyclic voltammetry was used to characterize the electrochemical behavior of MCZ and ETU, and square-wave adsorptive stripping voltammetry (SWAdSV) was employed for MCZ quantification in commercial formulations. It was found that both MCZ and ETU are irreversibly reduced (− 0.6 V and − 0.5 V vs Ag/AgCl, respectively) at the surface of a glassy carbon electrode in a mainly diffusion-controlled process, presenting maximum peak current intensities at pH 7.0 (in phosphate buffered saline electrolyte). Several parameters of the SWAdSV technique were optimized and linear relationships between concentration and peak current intensity were established between 10–90 μmol L− 1 and 10–110 μmol L− 1 for MCZ and ETU, respectively. The limits of detection were 7.0 μmol L− 1 for MCZ and 7.8 μmol L− 1 for ETU. The optimized method for MCZ was successfully applied to the quantification of this pesticide in two commercial formulations. The developed procedures provided accurate and precise results and could be interesting alternatives to the established methods for quality control of the studied products, as well as for analysis of MCZ and ETU in environmental samples.

Low-Spin Heme b3 in the Catalytic Center of Nitric Oxide Reductase from Pseudomonas nautica

Biochemistry, 2011, 50 (20), pp 4251–4262 DOI: 10.1021/bi101605p

A new CuZ active form in the catalytic reduction of N2O by nitrous oxide reductase from Pseudomonas nautica

J Biol Inorg Chem (2010) 15:967–976 DOI 10.1007/s00775-010-0658-6

Periplasmic nitrate reductase revisited: a sulfur atom completes the sixth coordination of the catalytic molybdenum

J Biol Inorg Chem. 2008 Jun;13(5):737-53. doi: 10.1007/s00775-008-0359-6

Strategies for the enhancement of the catalytic performance of cutinase in nonaqueous media

Dissertação para obtenção do Grau de Doutor em Engenharia Química e Bioquímica

Insights into Campylobacter jejuni Desulforubrerythrin catalytic mechanism

Dissertation presented to obtain the Master Degree in Molecular Genetics and Biomedicine