Copper coordination polymers from cavitand ligands: hierarchical spaces from cage and capsule motifs,and other topologies

The cyclotriveratrylene-type ligands (±)-tris(iso-nicotinoyl)cyclotriguaiacylene L1 (±)-tris(4-pyridylmethyl)cyclotriguaiacylene L2 and (±)-tris{4-(4-pyridyl)benzyl}cyclotriguaiacylene L3 all feature 4-pyridyl donor groups and all form coordination polymers with Cu^I and/or Cu^II cations that show a remarkable range of framework topologies and structures. Complex [Cu^I ₄Cu^II _1.5(L1)₃(CN)₆]·CN·n(DMF) 1 features a novel 3,4-connected framework of cyano-linked hexagonal metallo-cages. In complexes [Cu₃(L2)₄(H₂O)₃]·6(OTf)·n(DMSO) 2 and [Cu₂(L3)₂Br₂(H₂O)(DMSO)]·2Br·n(DMSO) 3 capsule-like metallo-cryptophane motifs are formed which linked through their metal vertices into a hexagonal 2D network of (4³.12³)(4².12²) topology or a coordination chain. Complex [Cu₂(L1)₂(OTf)₂(NMP)₂(H₂O)₂]·2(OTf)·2NMP 4 has an interpenetrating 2D 3,4-connected framework of (4.6².8)(6².8)(4.6².8²) topology with tubular channels. Complex [Cu(L1)(NCMe)]·BF₄·2(CH₃CN)·H₂O 5 features a 2D network of 6³ topology while the Cu^II analogue [Cu₂(L1)₂(NMP)(H₂O)]·4BF₄·12NMP·1.5H₂O 6 has an interpenetrating (10,3)-b type structure and complex [Cu₂(L2)₂Br₃(DMSO)]·Br·n(DMSO) 7 has a 2D network of 4.8² topology. Strategies for formation of coordination polymers with hierarchical spaces emerge in this work and complex 2 is shown to absorb fullerene-C₆₀ through soaking the crystals in a toluene solution.     

Water‐Soluble Triazabutadienes that Release Diazonium Species upon Protonation under Physiologically Relevant Conditions

Triazabutadienes are an understudied structural motif that have remarkable reactivity once rendered water‐soluble. It is shown that these molecules readily release diazonium species in a pH‐dependent manner in a series of buffer solutions with pH ranges similar to those found in cells. Upon further development, we expect that this process will be well suited to cargo‐release strategies and organelle‐specific bioconjugation reactions. These compounds offer one of the mildest ways of generating diazonium species in aqueous solutions.     

The rotational spectrum and hyperfine structure of arsenic monophosphide, AsP

Arsenic monophosphide has been prepared by laser ablation of arsenic in the presence of PH₃. The J = 2-1 and 1-0 transitions in both the ground and first excited vibrational states have been measured with a cavity pulsed jet Fourier-transform microwave spectrometer. An improved equilibrium internuclear distance (r_e) has been obtained. Hyperfine structure in the rotational spectrum of AsP has been resolved and has led to the first determinations of the As nuclear quadrupole coupling constant and both nuclear spin-rotation constants. The data enable the electronic structure of AsP to be compared with those of other mixed Group 15 diatomic molecules.     

Identification of bubble evolution mechanisms during AC electrograining

Bubble evolution during AC-graining is analysed in combination with the variation of the anodic peaks of the potential and the electrode surface morphology. Aluminium samples are grained in hydrochloric acid in an Inverted Rotating Disk Electrode. A roughness tester is used to characterise the electrode surface, while shadow imaging is applied to determine the bubble size distribution. An interpretation of the correlation existing among bubble size, potential peaks evolution, surface properties and smut layer formation is proposed, which provides insights into the mechanisms involved in bubble formation.     

NMR spectra of seleninium and 1- and 2-benzoseleninium cations

The analysis of the NMR spectra of seleninium and 1-and 2-benzoseleninium cations, recorded in deuterotrifluoroacetic acid, is reported. The effects of condensation on the spectral parameters of the protons of the seleninium ring were examined with particular reference to the shift to higher values of δ: this was consistent with the q values calculated by the HMO method. The ³J(HH) and ⁴J(HH) variations, including an interesting variation regarding the through-selenium ⁴J coupling, are also discussed.     

The acid dissolution of sulfide mineral samples under pressure in a microwave oven

A system for the rapid dissolution of sulfide samples from mines, mills and smelters is described. The samples and an acid mixture are placed in sealed teflon-PFA vessels, which are then heated in a microwave oven for 3 min. Following the dissolution, metals of interest (copper and nickel) are quantified by atomic absorption spectrometry. The system described produces significant savings in time and materials and increased output and efficiency in comparison with traditional methods; it is also much cleaner. Results are similar to those obtained with a more conventional dissolution method     

Use of carboxylic group functionalized magnetic nanoparticles for the preconcentration of metals in juice samples prior to the determination by capillary electrophoresis

Nowadays food industry demands reliable and precise methods to resolve problems related to quality and security control. The pretreatment steps, prior to sample analysis, are necessary to extract the target analytes because of the complexities of the food samples matrices. In this work, we have studied, for the first time, the potential of carboxylic group functionalized magnetic nanoparticles to preconcentrate metals from liquid samples before CE analysis. For the extraction of metals, 10 mL of an aqueous sample containing the metal mixture was added to 2 mg carboxylic group functionalized magnetic nanoparticles. Metals retained in the nanoparticles were re-extracted with 200 μL solution consisting of 0.8 mM 1,10-phenanthroline and 0.04% hydroxylamine chloride at pH 2. The electrophoretic buffer used in this work to separate different metals (Co, Cu, Zn, Ni, and Cd) consisted of 30 mM hydroxylamine chloride, 0.30 mM 1,10-phenanthroline, 80 mM urea, 15 mM ammonium chloride, and 0.1% methanol at pH 3.6. Finally, measurements were made at 270 nm. Under the optimized conditions, detection limits for Co, Zn, Cu, Ni, and Cd were 0.004, 0.003, 0.004, 0.008, and 0.009 mg L(-1) , respectively.     

Sensitization of lanthanides by nonnatural amino acids

The sensitization of Eu(III) and Tb(III) by ethylenediaminetetraaceticacid (EDTA)-derivatized tryptophan (Trp), 7-azatryptophan (7AW) and 5-hydroxytryptophan (5HW) has been examined. These Trp analogs were utilized in the present study because they can be incorporated into proteins in place of native Trp residues and because they absorb strongly beyond 305 nm (where Trp absorbance goes to zero), allowing selective excitation of such species in the presence of other Trp-containing proteins. All three indole derivatives were able to sensitize Tb(III) luminescence, with the relative sensitization being in the order Trp > 5HW > 7AW. On the other hand, only the 7AW-EDTA complex was able to sensitize Eu(III) luminescence, likely owing to a better spectral overlap between 7AW emission and Eu(III) absorbance. The sensitized emission of Tb(III) and Eu(II) displayed the expected long emission lifetimes at 545 nm [for Tb(III)] and 617 nm [for Eu(III)], indicating that long-lifetime lanthanide emission could be produced using nonnatural amino-acid donors. Thus, 7AW- and 5HW-sensitized lanthanide emissions should prove to be useful in biophysical studies, such as the use of fluorescence energy transfer to probe biomolecular interactions in vivo.     

Space and time resolved discharge evolution of a large volume X-ray triggered XeCl laser system

The spatial distribution and the temporal development of the net gain have been measured in a ten liter active volume switchless discharge XeCl laser. The experimental results are compared with both zero-dimensional and two-dimensional kinetic code predictions. The comparison between the results of the kinetic codes and of some measurements relevant to the time-dependent discharge homogeneity allows a deeper insight into the influence of the streamer evolution on the discharge characteristics.ENEA StudentENEA Guest