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1. Tri‐ and Hexadentate Poly‐Lewis Acids – Attempts to Unravel the Complex Dynamics of Cage and Capsule Formation in Solution.

Author

Klingsiek, Maximilian J., Franke, Maurice, Walkenhorst, Simon M., Röhr, Tobias, Buth, Julian, Mix, Andreas, Lamm, Jan‐Hendrik, Neumann, Beate, Stammler, Hans‐Georg, and Mitzel, Norbert W.

Subjects
LEWIS bases, ALUMINUM hydride, LEWIS acids, EXCHANGE reactions, NUCLEAR magnetic resonance spectroscopy
Abstract

Two tri‐ and two hexadentate poly‐Lewis acids (PLAs) with calyx‐like structures of C3 symmetry containing aluminum‐ and boron‐containing Lewis acidic functions were prepared by tin‐metal exchange reactions. The triply hydrosilylated [12]annulene served as basic framework. It forms a calyx‐like structure by the stereo‐ and regioselective attachment of three SiMeCl2 groups to the planar [12]annulene. The PLA precursors were generated by attaching three or six trimethylstannylethynyl groups to the silicon atoms. Lewis acid functions were introduced using the reagents bis‐(bis(trimethylsilyl)methyl)aluminium hydride (HAl[CH(SiMe3)2]2) and catecholatochloroborane (ClBCat). The complexation behavior of the PLAs towards different Lewis bases was investigated by NMR. Bases included pyridine, polydentate nitrogen‐ and phosphorus‐containing bases. Additionally, three molecules of a bidentate phosphorus‐containing base were captured with hexadentate PLAs. Diffusion NMR experiments provided insight into the aggregation processes: some of the adducts had a significantly larger volume than expected, indicating the formation of larger adducts than the expected 1 : 1 adduct, including larger 2 : 2 adduct cages. The distances between the Lewis acid units and the steric requirement of the attached substituents determine the complexation behavior of the PLAs. Thus, the weak Lewis acidic BCat units show no (tridentate case) or a strong (hexadentate case) interaction with PMe2‐containing bases, if they can act cooperatively. [ABSTRACT FROM AUTHOR]

Published
2024
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2. Kreislaufwirtschaft nach dem Cradle-to-Cradle-Vorbild: Wie kann ein geschlossener Ressourcenkreislauf erreicht werden?: Eine Untersuchung unternehmerischer Konzepte mit Beispielen aus der Praxis

Author

Röhr, Tobias

Subjects
Circular economy, cradle-to-cradle, design for disassembly, product service systems, take-back, reverse logistics, Kreislaufwirtschaft, Cradle-to-Cradle, Design für Demontage, Produkt-Service-Systeme, Take-back, Reverse Logistics, ddc:330, ddc:300, ddc:658, Kreislaufwirtschaft, Ressourcen, Demontage, Rücknahme, Reverse Logistik
Abstract

Das aktuell vorherrschende lineare Wirtschaftsprinzip ist für viele Umweltprobleme verantwortlich. Neben der immensen Umweltverschmutzung sorgt der stetig wachsende Ressourcenverbrauch für eine zunehmende Verknappung vieler wertvoller Rohstoffe. Ein intelligentes Kreislaufwirtschaftskonzept wie Cradle-to-Cradle kann diesen Problemen entgegenwirken. Für eine erfolgreiche Umsetzung von Cradle-to-Cradle werden unternehmerische Ansätze benötigt. Im Rahmen dieses Artikels werden vier Konzepte untersucht, die in einer Kreislaufwirtschaft implementiert werden können. Diese sind Design für Demontage, Produkt-Service-Systeme, Take-back Strategien und Reverse Logistics. Für jeden dieser vier Ansätze werden die Voraussetzungen sowie Barrieren hinsichtlich der Umsetzung innerhalb eines Kreislaufwirtschaftssystems aufgezeigt. Zudem wird dargelegt, dass sie im Cradle-to-Cradle-System realisierbar sind. Weiterhin werden reale Beispiele in Form von Unternehmen vorgestellt, die die verschiedenen Modelle bereits erfolgreich umgesetzt haben. Alle vier untersuchten Konzepte sind für ein Kreislaufwirtschaftssystem unter Beachtung der Cradle-to-Cradle-Kriterien geeignet. The currently prevailing linear economic principle is responsible for many environmental problems. In addition to the immense environmental pollution, the constantly growing consumption of resources is causing an increasing shortage of many valuable raw materials. An intelligent circular economy concept such as Cradle to Cradle can counteract these problems. Entrepreneurial approaches are needed for a successful implementation of Cradle to Cradle. This article examines four concepts that can be implemented in a circular economy. These are design for disassembly, product service systems, take-back strategies, and reverse logistics. For each of these four approaches, the prerequisites as well as barriers regarding the implementation within a circular economy system are shown. In addition, it is shown that they can be implemented in a cradle-to-cradle system. Furthermore, real examples are presented as companies that have already successfully implemented the various models. All four concepts examined are suitable for a circular economy system in compliance with the Cradle to Cradle criteria.

Published
2021

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