Intervalence (Charge-Resonance) Transitions in Organic Mixed-Valence Systems. Through-Space versus Through-Bond Electron Transfer between Bridged Aromatic (Redox) Centers

Intervalence absorption bands appearing in the diagnostic near-IR region are consistently observed in the electronic spectra of mixed-valence systems containing a pair of aromatic redox centers (Ar•+/Ar) that are connected by two basically different types of molecular bridges. The through-space pathway for intramolecular electron transfer is dictated by an o-xylylene bridge in the mixed-valence cation radical 3•+ with Ar = 2,5-dimethoxy-p-tolyl (T), in which conformational mobility allows the proximal syn disposition of planar T•+/T redox centers. Four independent experimental probes indicate the large through-space electronic interaction between such cofacial Ar•+/Ar redox centers from the measurements of (a) sizable potential splitting in the cyclic voltammogram, (b) quinonoidal distortion of T•+/T centers by X-ray crystallography, (c) “doubling” of the ESR hyperfine splittings, and (d) a pronounced intervalence charge-resonance band. The through (br)-bond pathway for intramolecular electron transfer is enforced in the mixed-valence cation radical 2a•+ by the p-phenylene bridge which provides the structurally inflexible and linear connection between Ar•+/Ar redox centers. The direct comparison of intramolecular rates of electron transfer (kET) between identical T•+/T centers in 3•+ and 2a•+indicates that through-space and through-bond mechanisms are equally effective, despite widely different separations between their redox centers. The same picture obtains for 3•+ and 2a•+from theoretical computations of the first-order rate constants for intramolecular electron transfer from Marcus−Hush theory using the electronic coupling elements evaluated from the diagnostic intervalence (charge-transfer) transitions. Such a strong coherence between theory and experiment also applies to the mixed-valence cation radical 7•+, in which the aromatic redox S center is sterically encumbered by annulation

A Thallium Mediated Route to \u3cem\u3eσ\u3c/em\u3e-Arylalkynyl Complexes of Bipyridyltricarbonylrhenium(I)

A simple, one-pot preparation of rhenium(I) σ-arylalkynyl complexes is reported using thallium(I) hexafluorophosphate as a halogen abstraction agent. This new route to rhenium σ-alkynyls enjoys higher yields compared to analogous preparations using silver salts by eliminating potential electrochemical degradation pathways

Structure of 5-nitro-2-tosylaminobenzaldehyde di(morpholin-4-yl)aminal Complex with Carbon Tetrachloride

The 5-nitro-2-tosylaminobenzaldehyde di(morpholin-4-yl)aminal forms a stable complex with carbon tetrachloride in the crystal phase. X-ray structural study of this complex indicates an essentially shortened intermolecular contact of 2.89 Å between the oxygen atom of the nitro group and one of the chlorine atom of the CCI4 molecule. Quantum-chemical calculations by semiempirical AMI method showed that the formation of such complex did not cause considerable decrease of system energy or change of charge distribution in molecules. It was supposed that this associate has van der Waals character

Structural Classification of Metal Complexes with Three-Coordinate Centres

Attempts to describe the geometry about three-coordinate silver(I) complexes have proven difficult because interatomic angles generally vary wildly and there is no adequate or readily available classification system found in the literature. A search of the Cambridge Structural Database shows that complexes formed between any metal centre and three non-metal donors (18001 examples) usually adopt geometries that are quite different than ideal ‘textbook’ extremes of either trigonal planar (∼4% with α = β = γ = 120 ± 2°), T-shaped (∼0.05% with α = 180 ± 2°, β = γ = 90 ± 2°), or trigonal pyramidal (∼0.3% with α = β = γ = 110 ± 2°). Moreover, there are multiple variations of “Y-type” and “other” shapes that require elaboration. Thus, to assist in future structural descriptions, we developed a classification system that spans all known and yet-to-be-discovered three-coordinate geometries. A spreadsheet has also been constructed that utilizes the “shape-space” approach to extract the structural description from a user input of three angles about a tri-coordinate centre and the number of atoms in a plane. The structures of two silver(I) complexes of new N-donor ligands p-NH2C6H4C6H4CH(pz = pyrazol-1-yl)2, L1, and 2-ferrocenyl-4,5-di(2-pyridyl)imidazole, L2, illustrate the utility of this classification system

Assessing the antibiotic potential of essential oils against Haemophilus ducreyi

BACKGROUND: Haemophilus ducreyi is the bacterium responsible for the genital ulcer disease chancroid, a cofactor for the transmission of HIV, and it is resistant to many antibiotics. With the goal of exploring possible alternative treatments, we tested essential oils (EOs) for their efficacy as antimicrobial agents against H. ducreyi. METHODS: We determine the minimum inhibitory concentration (MIC) of Cinnamomum verum (cinnamon), Eugenia caryophyllus (clove) and Thymus satureioides (thyme) oil against 9 strains of H. ducreyi using the agar dilution method. We also determined the minimum lethal concentration for each oil by subculturing from the MIC plates onto fresh agar without essential oil. For both tests, we used a 2-way ANOVA to evaluate whether antibiotic-resistant strains had a different sensitivity to the oils relative to non-resistant strains. RESULTS: All 3 oils demonstrated excellent activity against H. ducreyi, with MICs of 0.05 to 0.52 mg/mL and MLCs of 0.1-0.5 mg/mL. Antibiotic-resistant strains of H. ducreyi were equally susceptible to these 3 essential oils relative to non-resistant strains (p = 0.409). CONCLUSION: E. caryophyllus, C. verum and T. satureioides oils are promising alternatives to antibiotic treatment for chancroid

GeoBoids: A Mobile AR Application for Exergaming

“© © 2012 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.”We have designed a mobile Augmented Reality (AR) game which incorporates video see-through and spatialized audio AR techniques and encourages player movement in the real world. In the game, called GeoBoids, the player is surrounded by flocks of virtual creatures that are visible and audible through mobile AR application. The goal is for the player to run to the location of a GeoBoid swarm in the real world, capture all the creatures there, then run to the next swarm and repeat, before time runs out, encouraging the player to exercise during game play. The most novel elements of the game are the use of audio input and output for interacting with the creatures. The interface design of the game includes AR visualization, spatialized audio, touch gestures and whistle interaction. Feedback from users in a preliminary user study was mostly positive on overall game play and the design of the UI, while the results also revealed improvements were needed for whistle interaction and the visual design of the GeoBoids

Advancing the business and human rights agenda: Dialogue, empowerment, and constructive engagement

As corporations are going global, they are increasingly confronted with human rights challenges. As such, new ways to deal with human rights challenges in corporate operations must be developed as traditional governance mechanisms are not always able to tackle them. This article presents five different views on innovative solutions for the relationships between business and human rights that all build on empowerment, dialogue and constructive engagement. The different approaches highlight an emerging trend toward a more active role for corporations in the protection of human rights. The first examines the need for enhanced dialogue between corporations and their stakeholders. The next three each examine a different facet of empowerment, a critical factor for the respect and protection of human rights: empowerment of the poor, of communities, and of consumers. The final one presents a case study of constructive corporate engagement in Myanmar (Burma). Altogether, these research projects provide insight into the complex relationships between corporate operations and human rights, by highlighting the importance of stakeholder dialogue and empowerment. All the five projects were presented during the Second Swiss Master Class in Corporate Social Responsibility, held in Lausanne, Switzerland on December 12, 2008. The audience for this conference, which examined business and human rights, was composed of researchers, governmental representatives, and business and non-governmental organization practitioners