The Intermetalloid Cluster [(Cp*AlCu)6H4], Embedding a Cu6 Core Inside an Octahedral Al6 Shell: Molecular Models of Hume–Rothery Nanophases

Defined molecular models for the surface chemistry of Hume–Rothery nanophases related to catalysis are very rare. The Al‐Cu intermetalloid cluster [(Cp*AlCu)₆H₄] was selectively obtained from the clean reaction of [(Cp*Al)₄] and [(Ph₃PCuH)₆]. The stronger affinity of Cp*Al towards Cu sweeps the phosphine ligands from the copper hydride precursor and furnishes an octahedral Al₆ cage to encapsulate the Cu₆ core. The resulting hydrido cluster M₁₂H₄ reacts with benzonitrile to give the stoichiometric hydrometalation product [(Cp*AlCu)₆H₃(N=CHPh)].     

Health-Promoting Compounds in Stevia: The Effect of Mycorrhizal Symbiosis,Phosphorus Supply and Harvest Time

This work aimed to establish the synergic role of arbuscular mycorrhizal fungi (AMF) symbiosis, phosphorus (P) fertilization and harvest time on the contents of stevia secondary metabolites. Consequently, steviol glycosides (SVglys) concentration and profile, total phenols and flavonoids as well as antioxidant assays, have been assessed in inoculated and no-inoculated plants, grown with or without P supply and collected at different growth stages(69, 89 and 123 days after transplanting).The obtained results suggest that the synthesis of stevia secondary metabolites is induced and/or modulated by all the investigated variability factors. In particular, AMF symbiosis promoted total SVglys content and positively influenced the concentration of some minor compounds (steviolbioside, dulcoside A and rebaudioside B), indicating a clear effect of mycorrhizal inoculation on SVglys biosynthetic pathway. Interestingly, only the mycorrhizal plants were able to synthesize rebaudioside B. In addition, P supply provided the highest levels of total phenols and flavonoids at leaf level, together with the maximum in vitro antioxidant activities (FRAP and ORAC). Finally, the harvest time carried out during the full vegetative phase enhanced the entire composition of the phytocomplex (steviolbioside, dulcoside A, stevioside, rebaudioside A, B, C. total phenols and flavonoids). Moreover, polyphenols and SVglys appeared to be the main contributors to the in vitro antioxidant capacity, while only total phenols mostly contributed to the cellular antioxidant activity (CAA). These findings provide original information about the role played by AMF in association with P supply, in modulating the accumulation of bioactive compounds during stevia growth. At the cultivation level, the control of these preharvest factors, together with the most appropriate harvest time, can be used as tools for improving the nutraceutical value of raw material, with particular attention to its exploitation as functional ingredient for food and dietary supplements and cosmetics.     

Stability-Indicating LC-PDA Method for Determination of Idebenone in Nanoparticles Based on Chitosan and N-Carboxymethylchitosan

A forced degradation study of idebenone was conducted under conditions of UV irradiation, acid, basic and oxidative hydrolysis and in order to develop an isocratic stability-indicating LC-UV method for drug quantification in chitosan and N-carboxymethylchitosan nanoparticles obtained by spray drying. The drug was more labile to alkaline treatment than under the other forced degradation conditions. Idebenone and its degradation products were optimally resolved (resolution >4) on a Luna Phenomenex C₁₈ column with mobile phase composed by methanol:water: (80:20% v/v) at a flow rate of 1.0 mL min^?1, at 30 °C, using wavelength of 279 nm for drug detection. The method was linear, over a drug concentration range of 2 to 10 μg mL^?1. The RSD% value of intra- and inter-day precision studies was <1.5. The method showed excellent recoveries (99.4 to 101.1%). The LOD and LOQ values were found to be 0.18 and 0.59 μg mL^?1, respectively. In conclusion this method can be used as a rapid and accurate assay of idebenone in the nanoparticles during stability tests.     

Simultaneous saccharification and cofermentation of peracetic acid-pretreated biomass

Previous work in our laboratories has demonstrated the effectiveness of peracetic acid for improving enzymatic digestibility of lignocellulosic materials. The use of dilute alkali solutions as a pre-pretreatment prior to peracetic acid lignin oxidation increased carbohydrate hydrolysis yields in a synergistic as opposed to additive manner. Deacetylation of xylan is easily achieved using dilute alkali solutions under mild conditions. In this article, we evaluate the effectiveness of peracetic acid combined with an alkaline pre-pretreatment through simulataneous saccharification and cofermentation (SSCF) of pretreated hybrid poplar wood and sugar can ebagasse. Respective ethanol yields of 92.8 and 91.9% of theoretical are achieved using 6% NaOH/15% peracetic acid-pretreated substrates and recombinant Zymomonas mobilis CP4/p ZB5. Reduction of acetyl groups of the lignocellulosic materials is demonstrated following alkaline pre-pretreatments. Such processing may be helpful in reducing peracetic acid requirements. The influence of deacetylation is more significant in combined pretreatments using lower peracetic acid loadings.     

A Coordination Polymer of Vaska's Complex as a Heterogeneous Catalyst for the Reductive Formation of Enamines from Amides

Low-valent metal–organic frameworks (LVMOFs) and related materials have gained interest due to their potential applications in heterogeneous catalysis. However, of the few LVMOFs that have been reported, none have shown catalytic activity. Herein, a low-valent metal-organic material constructed from phosphine linkers and Ir^I nodes is reported. This material is effectively a crystalline, insoluble analogue of Vaska's complex. As such, the material reversibly binds O₂ and catalyzes the reductive formation of enamines from amides.     

Multimodal Analysis of Light-Driven Water Oxidation in Nanoporous Block Copolymer Membranes**

Heterogeneous light-driven catalysis is a cornerstone of sustainable energy conversion. Most catalytic studies focus on bulk analyses of the hydrogen and oxygen evolved, which impede the correlation of matrix heterogeneities, molecular features, and bulk reactivity. Here, we report studies of a heterogenized catalyst/photosensitizer system using a polyoxometalate water oxidation catalyst and a model, molecular photosensitizer that were co-immobilized within a nanoporous block copolymer membrane. Via operando scanning electrochemical microscopy (SECM), light-induced oxygen evolution was determined using sodium peroxodisulfate (Na₂S₂O₈) as sacrificial electron acceptor. Ex situ element analyses provided spatially resolved information on the local concentration and distribution of the molecular components. Infrared attenuated total reflection (IR-ATR) studies of the modified membranes showed no degradation of the water oxidation catalyst under the reported light-driven conditions.     

Enantioselective luminescence quenching of DNA light-switch [Ru(phen)2dppz]2+ by electron transfer to structural homologue [Ru(phendione)2dppz]2+

The quenching of the luminescence of [Ru(phen)(2)dppz](2+) by structural homologue [Ru(phendione)(2)dppz](2+), when both complexes are bound to DNA, has been studied for all four combinations of Delta and Lambda enantiomers. Flow linear dichroism spectroscopy (LD) indicates similar binding geometries for all the four compounds, with the dppz ligand fully intercalated between the DNA base pairs. A difference in the LD spectrum observed for the lowest-energy MLCT transition suggests that a transition, potentially related to the final localization of the excited electron to the dppz ligand in [Ru(phen)(2)dppz](2+), is overlaid by an orthogonally polarized transition in [Ru(phendione)(2)dppz](2+). This would be consistent with a low-lying LUMO of the phendione moiety of [Ru(phendione)(2)dppz](2+) that can accept the excited electron from [Ru(phen)(2)dppz](2+), thereby quenching the emission of the latter. The lifetime of excited Delta-[Ru(phen)(2)dppz](2+) is decreased moderately, from 664 to 427 ns, when bound simultaneously with the phendione complex to DNA. The 108 ns lifetime of opposite enantiomer, Lambda-[Ru(phen)(2)dppz](2+), is only shortened to 94 ns. These results are consistent with an average rate constant for electron transfer of approximately 1.10(6) s(-1) between the phenanthroline- and phendione-ruthenium complexes. At binding ratios close to saturation of DNA, the total emission of the two enantiomers is lowered equally much, but for the Lambda enantiomer, this is not paralleled by a decrease in luminescence lifetime. A binding isotherm simulation based on a generalized McGhee-von Hippel approach shows that the Delta enantiomer binds approximately 3 times stronger to DNA both for [Ru(phendione)(2)dppz](2+) and [Ru(phen)(2)dppz](2+). This explains the similar decrease in total emission, without the parallel decrease in lifetime for the Lambda enantiomer. The simulation also does not indicate any significant binding cooperativity, in contrast to the case when Delta-[Rh(phi)(2)bipy](3+) is used as quencher. The very slow electron transfer from [Ru(phen)(2)dppz](2+) to [Ru(phendione)(2)dppz](2+), compared to the case when [Rh(phi)(2)phen](3+) is the acceptor, can be explained by a much smaller driving free-energy difference.     

Copper Microelectrode as Liquid Chromatography Detector for Herbicide Glyphosate

Electrochemical behavior of herbicide glyphosate at copper microelectrode was investigated in alkaline and buffer solutions, and two mechanisms seemed to take place for glyphosate: i) complexation reaction at lower potential in alkaline and buffer solutions and ii) catalysis process at higher potential in alkaline solution. It was demonstrated that the copper microelectrode can be used as coulometric detector for glyphosate in HPLC, using the complexation reaction in buffer solution. Under optimized conditions, the detection limit for glyphosate was 5.9×10^?7 mol L^?1. The present method was successfully applied to the determination of glyphosate in tomato juice with a recovery of 88%.