Synthesis of Gold(I)−Trifluoromethyl Complexes and their Role in Generating Spectroscopic Evidence for a Gold(I)−Difluorocarbene Species

Readily prepared and bench-stable [Au(CF₃)(NHC)] compounds were synthesized by using new methods, starting from [Au(OH)(NHC)], [Au(Cl)(NHC)] or [Au(L)(NHC)]HF₂ precursors (NHC=N-heterocyclic carbene). The mechanism of formation of these species was investigated. Consequently, a new and straightforward strategy for the mild and selective cleavage of a single carbon/fluorine bond from [Au(CF₃)(NHC)] complexes was attempted and found to be reversible in the presence of an additional nucleophilic fluoride source. This straightforward technique has led to the unprecedented spectroscopic observation of a gold(I)−NHC difluorocarbene species.     

Ions generated from uranyl nitrate solutions by electrospray ionization (ESI) and detected with fourier transform ion-cyclotron resonance (FT-ICR) mass spectrometry

Electrospray ionization (ESI) of uranyl nitrate solutions generates a wide variety of positively and negatively charged ions, including complex adducts of uranyl ions with methoxy, hydroxy, and nitrate ligands. In the positive ion mode, ions detected by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry are sensitive to instrumental tuning parameters such as quadrupole operating frequency and trapping time. Positive ions correspond to oligomeric uranyl nitrate species that can be characterized as having a general formula of [(UO(2))(n)(A)(m)(CH(3)OH)(s)](+) or [(UO(2))(n)(O)(A)(m)(CH(3)OH)(s)](+) with n = 1-4, m = 1-7, s = 0 or 1, and A = OH, NO(3), CH(3)O or a combination of these, although the formation of NO(3)-containing species is preferred. In the negative ion mode, complexes of the form [(UO(2))(NO(3))(m)](-) (m = 1-3) are detected, although the formation of the oxo-containing ions [(UO(2))(O)(n)(NO(3))(m)](-) (n = 1-2, m = 1-2) and the hydroxy-containing ions [(UO(2))(OH)(n)(NO(3))(m)](-) (n = 1-2, m = 0-1) are also observed. The extent of coordinative unsaturation of both positive and negative ions can be determined by ligand association/exchange and H/D exchange experiments using D(2)O and CD(3)OD as neutral reaction partners in the gas-phase. Positive ions are of varying stability and reactivity and may fragment extensively upon collision with D(2)O, CD(3)OD and N(2) in sustained off-resonance irradiation/collision-induced dissociation (SORI-CID) experiments. Electron-transfer reactions, presumably occurring during electrospray ionization but also in SORI-CID, can result in reduction of U(VI) to U(V) and perhaps even U(IV).     

An Evolutionary Algorithm and discrete event simulation for optimizing inspection strategies for multi-stage processes

The problem of determining the optimal inspection strategy for a given multi-stage production process, i.e. the inspection strategy that results in the lowest total inspection cost, while still assuring a required output quality, is modelled as a joint optimization of inspection location, type and inspection limits. A fusion between a discrete event simulation to model the multi-stage process subject to inspection and to calculate the resulting inspection costs, and an Evolutionary Algorithm (EA) to optimize the inspection strategies, is suggested.     

A Highly Asymmetric Gold(III) η3‐Allyl Complex

A highly asymmetric Au^III η³‐allyl complex has been generated by treating Au(η¹‐allyl)Br(tpy) (tpy=2‐(p‐tolyl)pyridine) with AgNTf₂. The resulting η³‐allyl complex has been characterized by NMR spectroscopy and X‐ray crystallography. DFT calculations and variable temperature ¹H NMR suggest that the allyl ligand is highly fluxional.     

Tyrosine Side-Chain Functionalities at Distinct Positions Determine the Chirooptical Properties and Supramolecular Structures of Pentameric Oligothiophenes

Control over the photophysical properties and molecular organization of π-conjugated oligothiophenes is essential to their use in organic electronics. Herein we synthesized and characterized a variety of anionic pentameric oligothiophenes with different substitution patterns of L- or D-tyrosine at distinct positions along the thiophene backbone. Spectroscopic, microscopic, and theoretical studies of L- or D-tyrosine substituted pentameric oligothiophene conjugates revealed the formation of optically active π-stacked self-assembled aggregates under acid conditions. The distinct photophysical characteristics, as well as the supramolecular structures of the assemblies, were highly influenced by the positioning of the L- or D-tyrosine moieties along the thiophene backbone. Overall, the obtained results clearly demonstrate how fundamental changes in the position of the enantiomeric side-chain functionalities greatly affect the optical properties as well as the architecture of the self-assembled supramolecular structures.     

Acute Ultraviolet Radiation Perturbs Epithelialization but not the Biomechanical Strength of Full‐thickness Cutaneous Wounds

We hypothesized that priming of the skin with ultraviolet radiation (UVR) before being injured would enhance wound healing. Four groups, each comprising 20 immunocompetent hairless mice, were exposed to simulated solar irradiation in escalating UVR doses; 0 standard erythema dose (SED) = control, 1 SED, 3 SED and 5 SED. Twenty‐four hours after UV irradiation, inflammation was quantified by skin reflectance (erythema) and myeloperoxidase (MPO) tissue levels, and two 6 mm full‐thickness excisional wounds and one 3 cm incisional wound were inflicted. Epidermal hyperplasia was assessed by quantitative histology. Five days after wounding, wound coverage by neoepithelium and wound width of the excisional wounds was quantified in hematoxylin–eosin sections, and breaking strength was measured in strips from incisional wounds. Erythema (P < 0.001), MPO levels (P < 0.0005) and epidermal cell layers (P < 0.001) increased dose‐dependently by UV exposure of dorsal skin. In the excisional wounds, epithelial coverage decreased (P = 0.024) by increasing the UVR dose, whereas there was no significant difference (P = 0.765) in wound MPO levels. Neither wound width (P = 0.850) nor breaking strength (P = 0.320) differed among the groups. Solar‐simulated UVR 24 h before wounding impaired epithelialization but was not detrimental for surgical incisional wound healing.     

Solutions to the Quantum QSPR problem in molecular spaces

The molecular quantum similarity framework is used to present a new set of Quantum Quantitative Structure– Properties Relationship (QQSPR) procedures. The theoretical basis consists of the so-called fundamental QQSPR equation, deducible from quantum mechanical first principles, associated with the quantum mechanical expectation values computation. Approximate solutions of the fundamental QQSPR equation within direct and reciprocal spaces, containing molecular density functions, are studied in a common framework. Contribution to the Serafín Fraga Memorial Issue. This paper is dedicated to Serafín Fraga and Xavier Gironès, in memoriam. They have formed part of my life as a scientist: I had been an apprentice with the first and I tried to be a teacher with the second. I learned from both, though. They will be like stars in my mind, until we can walk together the endless path of nothingness.     

Comments on Chiral p-Forms

Two issues regarding chiral p-forms areaddressed. First, we investigate the topologicalconditions on spacetime under which the action for anonchiral p-form can be split as the sum of the actionsfor two chiral p-forms, one of each chirality. Whenthese conditions are not met, we exhibit explicitly theextra topological degrees of freedom and their couplingsto the chiral modes. Second, we study the problem of constructing Lorentz-invariantself-couplings of a chiral p-form in the light of theDirac-Schwinger condition on the energy-momentum tensorcommutation relations. We show how the Perry-Schwarz condition follows from the Dirac-Schwingercriterion and point out that consistency of thegravitational coupling is automatic.