Schade, Dustin
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Schade, Dustin
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Publication Access status: Metadata only , Extension of the π-system of monoaryl-substituted norbornadienes with acetylene bridges: influence on the photochemical conversion and storage of light energyThe photochromic norbornadiene/quadricyclane pair is a promising system for molecular solar thermal (MOST) energy storage, with which solar energy may be converted, stored, and released as heat in one integral molecular system. Herein, we present the synthesis of mono-, bis-, and tris-norbornadiene derivatives with alkynylbenzene and alkynylnaphthalene core units, along with studies of their photochemical properties. The target compounds were synthesized by Sonogashira–Hagihara coupling reactions of 2-bromonorbornadiene and the corresponding arylacetylenes. The norbornadienes showed absorption maxima in the range of 310–345 nm and long-wavelength zero onsets of up to 420 nm. The photoisomerization quantum yields were as high as 59% per photoisomerization event and the resulting quadricyclanes showed half-lives of up to 8 h at room temperature. Furthermore, the norbornadienes were transformed quantitatively into their quadricyclane photoproducts by irradiation with green light (520 nm) in the presence of a photosensitizer.Source Type:Article1 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Metadata only , Gilding the Lily: Studies on the Effects of Successive Loading of Light Energy‐Storing Molecules with Norbornadiene UnitsThe photochromic norbornadiene‐quadricyclane cycle has emerged as a promising basis for molecular solar thermal (MOST) energy storage. In this context, it has been established that multifunctional photoswitches with several norbornadiene units at one central aromatic core have favorable photochemical properties and storage capacities. Nevertheless, a maximum number of three norbornadiene units has been combined in one molecule, so far. In this work, scope and limits of this approach should be further assessed. Thus, exemplary polyfunctionalized derivatives have been synthesized by Suzuki‐Miyaura reactions, and their suitability for MOST applications was investigated. These compounds were converted into the corresponding quadricyclanes by direct UV irradiation ( λ ex =315 nm) with moderate quantum yields, whereas the reaction is more efficient upon irradiation with λ ex =520 nm in the presence of photosensitizers. But these molecules showed low stabilities and short half‐lives of 1 to 2 days. Moreover, the photochemical reaction is hampered by the close vicinity of photoactive units. Therefore, it appears that in such assemblies, a maximum number of three norbornadiene units is the limit to keep the optimal balance of photochemical properties required for MOST applications.Source Type:Article3
