A variable temperature study of Ru3(CO)12 in the solid state and the generation of alternative crystal structures

Summary The molecular and crystal structure of Ru₃(CO)₁₂ has been reinvestigated on single-crystal X-ray diffraction data collected at 100 and 150 K. Thermal motion analysis on high-order diffraction data have been used to characterize the motion about equilibrium positions of the molecule as a whole and of groups of atoms. It has been shown that, while the molecule undergoes an almost isotropic rigid-body librational and translational motion, the three Ru(CO)₄ units undergo different librational motions about the axes passing between each Ru atom and bisecting the opposite 615-01 bond. Packing potential energy calculations and computer graphics have been used to show that the most favoured packing motif in the experimental crystal is based on interlocking between tetracarbonyl units formed by two pairs of CO ligands at right angles along a 615-02 edge. Starting from the structure of Ru₃(CO)₁₂, alternative crystal arrangements have been generated and compared with the experimental crystal structure in terms of packing efficiency and cohesive energy.     

Exact expression for the diffusion propagator in a family of time-dependent anharmonic potentials

We have obtained the exact expression of the diffusion propagator in the time-dependent anharmonic potential V(x,t)=1 / 2a(t)x(2)+b ln x. The underlying Euclidean metric of the problem allows us to obtain analytical solutions for a whole family of the elastic parameter a(t), exploiting the relation between the path integral representation of the short time propagator and the modified Bessel functions. We have also analyzed the conditions for the appearance of a nonzero flow of particles through the infinite barrier located at the origin (b<0).     

Press-transferred carbon black nanoparticles on board of microfluidic chips for rapid and sensitive amperometric determination of phenyl carbamate pesticides in environmental samples

The authors describe a strategy for rapid and sensitive determination of phenyl carbamate pesticides in environmental samples. It consists of the following steps: (a) Enrichment and clean-up of the analytes using a C18 microtip based procedure; (b) alkaline hydrolysis of the carbamates (carbofuran, isoprocarb and carbaryl) to form phenol derivatives; and (c) fast separation and amperometric detection in a microfluidic chip (MCs). The microchips were fabricated by using press-transferred carbon black nanoparticles (CB-NPs) as electrochemical sensing nanomaterial. The excellent electrochemical behavior of the CB-NPs coupled to the microchip warrants good separation and allows for the voltammetric determination (best at a working voltage of +0.70 V vs Ag/AgCl) of the carbamates within < 6 min. The authors also describe a rapid procedure for the clean-up and enrichment of the carbamates from real samples by using a C18 microtip. The procedure allowed a 10-fold enrichment of the analytes, and this led to a detection limits in ?the 0.7 to 1.2 μM concentration range. The assay was applied to samples of river, lake and irrigation water that were spiked with carbamates at 50 and 100 μM levels. Recoveries are in the 87 to 108 % range, and RSDs (n = 3) in the 5 to 11 % range. The exploitation of the such nanomaterials coupled to microfluidics and microextraction procedures for real sample analysis in our preception represents a most viable tool for the analysis of complex real samples, for on-site environmental monitoring, and for rapid diagnosis.

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Graphical abstract Press-printed carbon black nanoparticles films on board of microfluidic chips.

     

Synthesis of pyrene—acridine bis-intercalators and effects of binding to DNA

A bis-intercalating compound containing pyrene and 9-aminoacridine chromophores (N-(5-(1-pyrenyl)-pentyl)-6-(9-acridinylamino) hexylamide, I), was prepared and its interaction with double-stranded DNA was investigated. Homologous compounds in which the two chromophores were connected by a linear carbon chain (pentamethylene (II), tetramethylene (III) and methylene (IV)) were also prepared. In acetonitrile solutions of the free ligands, the presence of the proximal pyrene results in reduced acridine fluorescence relative to 9methylaminoacridine (9-MAA), and the degree of quenching increases with decreasing chain length. The quenching process is assigned to exothermic electron transfer from pyrene to the excited 9-aminoacridine (9-AA) chromophore. In the presence of DNA, the relative quenching order is reversed, and I and IV are quenched more strongly than II and III. From linear dichroism experiments, it is concluded that I binds by bis-intercalation of the pyrene and acridine moieties, III and IV undergo intercalation of the acridine chromophore and II binds by partial bis-intercalation at two contiguous sites.     

Synthesis, characterization, and structure of a new N-nitrosamine of cyclam (1,4,8,11-tetraazacyclotetradecane)

A novel N-nitrosamine of cyclam has been synthesized. The N-N bond lengths values, as determined from the X-ray crystal structure, fall in the 1.318(2) and 1.320(2) Å range, smaller than the ones expected for the N-N single bond. The N-NO bond angles are in the 115.0(1)° and 114.8(1)° range. The νNO, νNN, and δN-NO vibrational modes were observed in the infrared spectrum at 1454, 1139, and 555 cm⁻¹, respectively. The photolysis of the cyclam(NO)₄ compound gives rise to the nitrosyl release through an heterolytic cleavage of the N-NO bonds, as indicated by the appearance of the νNO⁺ band at 2228 cm⁻¹ at the expense of decreasing the νNO, νNN, and δN-NO bands.     

Hopf Categories

We introduce Hopf categories enriched over braided monoidal categories. The notion is linked to several recently developed notions in Hopf algebra theory, such as Hopf group (co)algebras, weak Hopf algebras and duoidal categories. We generalize the fundamental theorem for Hopf modules and some of its applications to Hopf categories.     

Mononuclear and heterodinuclear phenanthrolinedione complexes of <Emphasis Type="Italic">d</Emphasis>- and <Emphasis Type="Italic">f</Emphasis>-block elements

1,10-Phenanthroline-5,6-dione (Phd) complexes of group 3 and lanthanide elements having formulae Ln(hfac)₃(Phd) (Ln = Y, Eu, Yb; hfac = hexafluoroacetylacetonate) were synthesised and characterised. Complexes of d-block elements of the type [MCl(Phd)(p-cymene)]⁺ (M = Ru, Os) were also prepared. In all these species, coordination of the polydentate ligand occurs by the N-donor moieties, as indicated by DFT calculations. The novel compounds were tested, together with fac-ReBr(Phd)(CO)₃, as precursors for the preparation of heterobimetallic d/f derivatives. The reaction of the rhenium complex with yttrium or lanthanide anhydrous triflate salts led to the formation of the complexes ReBr(CO)₃(N,N′-Phd-O,O′)Ln(OTf)₃(THF) (Ln = Y, Eu, Yb), where the trivalent ions interacted with the quinonoid moiety. The redox properties of the rhenium centre were strongly affected by the coordination of Ln(OTf)₃, as observed by comparing the cyclic voltammetry measurements carried out on fac-ReBr(Phd)(CO)₃ and on ReBr(CO)₃(N,N′-Phd-O,O′)Y(OTf)₃.     

Sintering and electrical conductivity of gadolinia-doped ceria

Bulk specimens of Ce_0.9Gd_0.1O_2-δ prepared with powders within a range of specific surface area were sintered in oxidizing, inert, and reducing atmospheres. The aim of this work is to investigate the effects of the sintering atmosphere on the microstructure and grain and grain boundary conductivities of the solid electrolyte. The lattice parameter determined by Rietveld refinement is 0.5420(1) nm, and the microstrain was found negligible in the powder materials. Specimens sintered in the Ar/4 % H₂ mixture display larger average grain sizes independent on the particle size of the starting powders. The grain and grain boundary conductivities of specimens sintered under reducing atmosphere are remarkably lower than those sintered under oxidizing and inert atmospheres. The activation energy (～0.90 eV) for total electrical conductivity remains unchanged with both the initial particle size and the sintering atmosphere.