Paululat, Thomas
Preferred name
Paululat, Thomas
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Publication Access status: Metadata only , Bis‐ and Tris‐norbornadienes with High Energy Densities for Efficient Molecular Solar Thermal Energy StorageMolecular solar thermal energy storage (MOST) systems can convert, store and release solar energy in chemical bonds, i.e., as chemical energy. In this work, phenyl‐ and naphthyl‐linked bis‐ and tris‐norbornadienes are presented as promising MOST systems with very high energy densities. The substrates were synthesized by Suzuki–Miyaura coupling reactions and their absorption properties and characteristic parameters for MOST applications were investigated. The norbornadiene derivatives showed absorption onsets of up to 386 nm and photoisomerization quantum yields of 56 % per photoisomerization event. The resulting quadricyclane products have half‐lifes up to 14 d and very high energy densities of up to 734 kJ/kg. Overall, these norbornadienes fulfill necessary criteria for an optimal MOST system and are, therefore, a highly promising basis for the development of materials for efficient solar energy conversion and storage.Source Type:Article3 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Metadata only , Reversible Restrain and Release of the Dynamic Valence Isomerization in a Shape‐shifting Bullvalene by Complex FormationIn search for structural features that enable the control of the valence isomerization of the fluxional bullvalene, a bullvalene‐bis(harmane) conjugate is identified that acts as chelating ligand in complexes with metal ions. Spectrometric titrations show that this ligand forms 1 : 1 complexes with Ag + , Cu + , Cu 2+ , and Zn 2+ . Most importantly, detailed NMR‐spectroscopic analysis at different temperatures reveals that the complexation with Ag + strongly affects the dynamic isomerization of the bullvalene unit of the ligand such that only one predominant valence isomer is formed, even at 5 °C. Detailed 1 H‐NMR‐spectroscopic studies disclose an increased barrier (~11 kJ mol −1 ) of the Cope rearrangement. Furthermore, the addition of hexacyclene displaces the Ag + from the complex, so that the valence isomerization is accelerated and an equilibrium with two predominant isomers is formed. In turn, repeated addition of Ag + regains the complex with the restrained isomerization of the bullvalene unit. This method to control the valence isomerism by straightforward chemical stimuli may be used to simplify structural analysis at elevated temperatures, i. e. a feature not available so far with bullvalenes, and it may be employed as functional element in dynamic supramolecular assemblies.Source Type:Article1
