Molecular and supported ruthenium complexes as photoredox oxidation catalysts in water

Abstract

A new bidentate pyridylpyrazole ligand functionalized with the pyrene group, 3-(2-pyridyl)-1-(pyrazolyl)methylpyrene (pypz-pyr), has been synthetized, togheter with a successful homogeneous photoredox catalyst containing the above ligand and the tridentate terpyridine...

Enhancing Photoredox Catalysis in Aqueous Environments: Ruthenium Aqua Complex Derivatization of Graphene Oxide and Graphite Rods for Efficient Visible-Light-Driven Hybrid Catalysts

“…In both compounds, the presence of an alkyl pyrene substituent at the N -tridentate ligand induces an hypsochromic shift of the MLCT absorptions with regard to the analogous complex bearing the bpea ligand, , which is consistent with the lower electron density donation from the ligand to the metal. A similar behavior is observed in other complexes containing the pyrene group …”

“…Nevertheless, the selectivity observed in all cases was consistently >99%. It is worth mentioning the high TON observed with these systems, being among the highest reported for the photooxidation of alcohols in the heterogeneous phase. ,,, We attempted to reuse the aqua ruthenium graphite rod in the photooxidation of 4-methylbenzyl alcohol. However, the GR@trans-fac- 3 photocatalyst exhibited a remarkable decrease in activity after the third run, with conversions of 68% in the first run, 48% in the second run, and 23% in the third run.…”

“…Both systems involve a two-electron two proton-coupled process . Cooperative photoredox catalysis based on ruthenium compounds are the systems most commonly studied in photooxidation of organic substrates, which involve a photocatalyst, acting as the light-harvesting antenna, combined with a transition metal catalyst, which can activate the organic substrate through proton-coupled electron transfer (PCET) mechanisms. − However, in photooxidation catalysis, there are few examples where only one photocatalyst participates in the process − and, specifically, few ruthenium photocatalysts based on polypyridyl ligands acting as both photosensitizers and catalysts have been described in the literature − and scarcely are those based on ruthenium aqua complexes. , …”

Development of a General Procedure To Access Recoverable Solid-Supported Photocatalysts for Use in Organic Synthesis

“…For the development of an organic SSPC, the commercially available and well-precedented (3-aminopropyl)triethoxysilane (APTES) 17−20 was selected as the solid-support system linker due to the ease of synthesis when compared to other forms of solid support. 21 Xanthylium (1) was chosen as a representative photocatalyst due to the markedly high redox potential of its corresponding N-alkyl acridinium product ([ t Bu-Acr-Mes] + BF 4…”

“…In designing recyclable photocatalysts, we set out to synthesize catalysts that incorporated a solid-support system, while retaining the photoredox-active characteristics of their progenitors. For the development of an organic SSPC, the commercially available and well-precedented (3-aminopropyl)­triethoxysilane (APTES) − was selected as the solid-support system linker due to the ease of synthesis when compared to other forms of solid support . Xanthylium ( 1 ) was chosen as a representative photocatalyst due to the markedly high redox potential of its corresponding N -alkyl acridinium product ([ t Bu-Acr-Mes] + BF 4 – , E 0 = 2.07 V vs saturated calomel electrode (SCE)) when compared to other common xanthenes .…”