Cyclic Elements in MV-Algebras and Post Algebras

In this paper we characterize the MV-algebras containing as subalgebras Post algebras of finitely many orders. For this we study cyclic elements in MV-algebras which are the generators of the fundamental chain of the Post algebras. Mathematics Subject Classification: 03G20, 03G25, 06D25, 06D30, 06F15, 06F35.     

Ecotoxicity of, and remediation with, engineered inorganic nanoparticles in the environment

This article presents recent developments on the use of inorganic nanoparticles (NPs) for environmental remediation in polluted soil, water and gas. The number of publications on these topics has grown exponentially in recent years, especially those focused on wastewater treatment. Among these topics, removal of metals has become the most popular, although some works relate to the use of nanomaterials for the elimination of nutrients (e.g., nitrogen and some persistent organic pollutants). However, this growth has not been accompanied by knowledge about the behavior of NPs once used and released into the environment. In this article, we also comment upon the current situation with respect to NP toxicology (nanotoxicology). A remarkable number of different toxicology tests has been applied to NPs, often making it very difficult to interpret or to generalize the results. We analyze in detail the bioluminescence, Daphnia magna and other tests, and give some preliminary results obtained in our work.     

A new dinuclear Ru-Hbpp based water oxidation catalyst with a trans-disposition of the Ru-OH

The bis(2-pyridyl)ethylamine (bpea) ligand has been used as a starting material for the synthesis of dinuclear Ru complexes of general formula trans,fac-{[Ru(n)X(bpea)](2)(μ-bpp)}(m+) (for X = Cl, n = II, m = 1, trans-Ru(II)-Cl, 1(+); for X = OH, n = III, m = 3, trans-Ru(III)-OH, 2(3+)) where the 3,5-bis(2-pyridyl)pyrazolate anionic ligand (bpp) acts as bridging dinucleating ligand, the bpea ligand coordinates in a facial manner and the monodentate ligands X are situated in a trans fashion with regard to one another. These complexes have been characterized in solution by 1D and 2D NMR spectroscopy, UV-vis and electrochemical techniques and in the solid state by X-ray diffraction analysis. The reaction of 1(PF(6)) with Ag(+) generates the corresponding solvated complex where the Cl ligand has been removed as insoluble AgCl, followed by the oxidation of Ru(II) to Ru(III) to generate the corresponding dinuclear complex trans-Ru(III)-OH, 2(PF(6))(3). The latter has been shown to catalytically oxidize water to molecular dioxygen using Ce(IV) as oxidant. Quantitative gas evolution as a function of time has been monitored on line by both manometry and mass spectroscopy (MS) techniques. Relative initial velocities of oxygen formation together with structural considerations rule out an intramolecular O-O bond formation pathway.     

Noisy colored point set matching

We propose a process for determining approximated matches, in terms of the bottleneck distance, under color preserving rigid motions, between two colored point sets A,B∈R², |A|≤|B|. We solve the matching problem by generating all representative motions that bring A close to a subset B^′ of set B and then using a graph matching algorithm. We also present an approximate matching algorithm with improved computational time. In order to get better running times for both algorithms we present a lossless filtering preprocessing step. By using it, we determine some candidate zones which are regions that contain a subset S of B such that A may match one or more subsets B^′ of S. Then, we solve the matching problem between A and every candidate zone. Experimental results using both synthetic and real data are reported to prove the effectiveness of the proposed approach.     

New ru(II) complexes containing oxazoline ligands as epoxidation catalysts. Influence of the substituents on the catalytic performance

The synthesis of a family of new Ru complexes containing the facial tridentate ligand with general formula [Ru(II)(T)(D)(X)](n+) (T = trispyrazolylmethane (tpm); D = ((4S,4'S)-(-)-4,4',5,5'-tetrahydro-4,4'-bis(1-methylethyl)-2,2'-bioxazole) (iPr-box-C) or N-(1-hydroxy-3-methylbutan-(2S)-(-)-2-yl)-(4S)-(-)-4-isopropyl-4,5-dihydrooxazole-2-carbimidate (iPr-box-O); X = Cl, H(2)O) has been described. All complexes have been spectroscopically characterized in solution through (1)H NMR and UV-vis techniques, and the redox properties of complexes have also been studied by means of cyclic voltammetry (CV). Furthermore, the chloro complexes presented here have been characterized in the solid state through monocrystal X-ray diffraction analysis. The oxazolinic iPr-box-C ligand undergoes a Ru-assisted hydrolysis reaction generating the corresponding amidate anionic ligand iPr-box-O, that keeps coordinated to the Ru metal center and that produces a strong σ-donation effect over it. The reactivity of the Ru-OH(2) complexes described in this paper together with other similar ones, previously synthesized by us, has been tested with regard to the epoxidation of different olefins. Complexes [Ru(II)(R-box-C)(tpm)OH(2)](BF(4))(2), R = Bz, 3'c/iPr, 3c, show high stereoselectivity in the epoxidation of cis-β-methylstyrene, with the exclusive formation of the cis-epoxide. However, there is a significant difference in regioselectivity between the two catalysts in the epoxidation of 4-vinylcyclohexene; complex 3'c leads to the regioselective oxidation at the ring alkene position, whereas complex 3c leads to the oxidation at the terminal position. Computational calculations indicate only small energy differences between the two possible products of 4-vinylcyclohexene epoxidation, but the energy barriers for the interaction of the catalytic systems with the alkene groups of 4-vinylcyclohexene agree with the reactivity differences found for the two catalysts having isopropyl or benzyl as substituent of the oxazole ligand. Computed local Fukui functions help to explain the observed reactivity trends.     

Synthesis, structure, and reactivity of new tetranuclear Ru-Hbpp-based water-oxidation catalysts

The preparation of three new octadentate tetranucleating ligands made out of two Ru-Hbpp-based units [where Hbpp is 3,5(bispyridyl)pyrazole], linked by a xylyl group attached at the pyrazolate moiety, of general formula (Hbpp)(2)-u-xyl (u = p, m, or o) is reported, together with its dinucleating counterpart substituted at the same position with a benzyl group, Hbpp-bz. All of these ligands have been characterized with the usual analytical and spectroscopic techniques. The corresponding tetranuclear ruthenium complexes of general formula {[Ru(2)(trpy)(2)(L)](2)(μ-(bpp)(2)-u-xyl)}(n+) [L = Cl or OAc, n = 4; L = (H(2)O)(2), n = 6] and their dinuclear homologues {[Ru(2)(trpy)(2)(L)](μ-bpp-bz)}(n+) [L = Cl or OAc, n = 2; L = (H(2)O)(2), n = 3] have also been prepared and thoroughly characterized both in solution and in the solid state. In solution, all of the complexes have been characterized spectroscopically by UV-vis and NMR and their redox properties investigated by means of cyclic voltammetry techniques. In the solid state, monocrystal X-ray diffraction analysis has been carried out for two dinuclear complexes {[Ru(2)(trpy)(2)(L)](μ-bpp-bz)}(2+) (L = Cl and OAc) and for the tetranuclear complex {[Ru(2)(trpy)(2)(μ-OAc)](2)(μ-(bpp)(2)-m-xyl)}(4+). The capacity of the tetranuclear aqua complexes {[Ru(2)(trpy)(2)(H(2)O)(2)](2)(μ-(bpp)(2)-u-xyl)}(6+) and the dinuclear homologue {[Ru(2)(trpy)(2)(H(2)O)(2)](μ-bpp-bz)}(3+) to act as water-oxidation catalysts has been evaluated using cerium(IV) as the chemical oxidant in pH = 1.0 triflic acid solutions. It is found that these complexes, besides generating significant amounts of dioxygen, also generate carbon dioxide. The relative ratio of [O(2)]/[CO(2)] is dependent not only on para, meta, or ortho substitution of the xylylic group but also on the concentration of the starting materials. With regard to the tetranuclear complexes, the one that contains the more sterically constrained ortho-substituted ligand generates the highest [O(2)]/[CO(2)] ratio.     

Tunable single-site ruthenium catalysts for efficient water oxidation

The catalytic water oxidation activity of mononuclear ruthenium complexes comprising a pyridine-functionalized abnormal triazolylidene ligand can be adjusted by modification of the triazolylidene substituents, which is readily achieved through click-type cycloaddition chemistry, affording some of the most active ruthenium catalysts known thus far for water oxidation (TONs > 400, TOFs close to 7000 h(-1)).     

Water oxidation in the context of the energy challenge: tailored transition-metal catalysts for oxygen-oxygen bond formation

Understanding water oxidation mechanisms: The power of two cooperating metal centers.     

A Self‐Improved Water‐Oxidation Catalyst: Is One Site Really Enough?

The homogeneous catalysis of water oxidation by transition‐metal complexes has experienced spectacular development over the last five years. Practical energy‐conversion schemes, however, require robust catalysts with large turnover frequencies. Herein we introduce a new oxidatively rugged and powerful dinuclear water‐oxidation catalyst that is generated by self‐assembly from a mononuclear catalyst during the catalytic process. Our kinetic and DFT computational analysis shows that two interconnected catalytic cycles coexist while the mononuclear system is slowly and irreversibly converted into the more stable dinuclear system: an extremely robust water‐oxidation catalyst that does not decompose over extended periods of time.