Consequences of the One‐Electron Reduction and Photoexcitation of Unsymmetric Bis‐imidazolium Salts

Coupling of uronium salts with in situ generated N‐heterocyclic carbenes provides straightforward access to symmetrical [ 4 ]²⁺ and unsymmetrical bis‐imidazolium salts [ 6 ]²⁺ and [ 9 ]²⁺. As indicated by cyclic and square‐wave voltammetry, [ 6 ]²⁺ and [ 9 ]²⁺ can be (irreversibly) reduced by one electron. The initially formed radicals [ 6 ]^.+ and [ 9 ]^.+ undergo further reactions, which were probed by EPR spectroscopy and density functional calculations. The final products of the two‐electron reduction are the two carbenes. Upon irradiation with UV light both [ 6 ]²⁺ and [ 9 ]²⁺ emit at room temperature in solution but with dramatically different characteristics. The different fluorescence behavior is analyzed by emission spectroscopy and interpreted by using time‐dependent density functional calculations as largely due to different excited‐state dynamics of [ 6 ]²⁺ and [ 9 ]²⁺. The geometries of both radicals [ 6 ]^.+ and [ 9 ]^.+ and excited states {[ 6 ]²⁺} * and {[ 9 ]²⁺}* are substantially different from those of the parent ground‐state molecules.     

Sustainable management of an alpine national park: handling the two-edged effect of tourism

Attracting visitors to an alpine national park can open up additional sources of funding for species conservation. However, tourism also brings ecologically negative impacts to the park and, in particular, to endangered species. In this paper, we discuss the handling of this two-edged effect of nature-based tourism within the context of a national park’s management decision. We develop a stylized model which frames the interaction of a representative largely unknown species, its habitat, and park visitors in an alpine ecosystem. In applying this to the protection of a rock partridge population in the Hohe Tauern National Park (Austria), we illustrate that a combined visitor and species protection policy can maximize steady state net benefits from tourism and conservation, while ensuring that the endangered species reaches its conservation target in the long run. Thus, even for a small, largely unknown species such as the rock partridge, and not only for popular species like the golden eagle, it is possible to endogenously generate a conservation budget by attracting visitors.     

Adsorber Particles with Magnetically-Supported Improved Electrochemical Conversion Behavior for Waste Water Treatment Processes

Micron-sized supraparticles, consisting of a plurality of discrete nano- and microscale functional units, are assembled and fused by means of a droplet extrusion process. By combining nano magnetite, activated carbon, and conductive carbon with a polymeric binder matrix, particles are obtained which unite good magnetic properties, electrical conductivity, and adsorber activity through the high accessible surface area of the incorporated activated carbon of about 570 m² g⁻¹, thereby enabling a new approach toward sustainable water treatment processes. Due to the interplay of the components, it is possible to adsorb target substances, dissolved in the water which is demonstrated by the adsorption of the model dye methylene blue. A very fast adsorption kinetic and an adsorption capacity of about 400 mg g⁻¹ is determined. By using the developed composite particles, it is also possible to electrochemically alter substances flowing through a magnetically-stabilized fluidized-bed reactor by electrochemically charging/discharging, significantly supported by the magnetic field enabling alternatingly optimum mobility/adsorption phases with contact/charging intervals. The electrochemical conversion can be increased up to 151% depending on the applied flow-rate and electrical voltage. By applying an external magnetic field, a further increase of electrochemical conversion of up to 70% can be observed.