Ruthenium Imidazophenanthrolinium Complexes with Prolonged Excited‐State Lifetimes

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Detailed investigations of a photocatalytic system capable of producing hydrogen under pre-catalytic aerobic conditions are reported. This system consists of the NHC precursor chromophore [Ru(tbbpy)2 (RR'ip)][PF6 ]3 (abbreviated as Ru(RR'ip)[PF6 ]3 ; tbbpy=4,4'-di-tert-butyl-2,2'-bipyridine, RR'ip=1,3-disubstituted-1H-imidazo[4,5-f][1,10]phenanthrolinium), the reduction catalyst Co(dmgH)2 (dmgH=dimethylglyoximato), and the electron donor ascorbic acid (AA). Screening studies with respect to solvent, cobaloxime catalyst, electron donor, pH, and concentrations of the individual components yielded optimized photocatalytic conditions. The system shows high activity based on Ru, with turnover numbers up to 2000 under oxygen-free and pre-catalytic aerobic conditions. The turnover frequency in the latter case was even higher than that for the oxygen-free catalyst system. The Ru complexes show high photostability and their first excited state is primarily located on the RR'ip ligand. X-ray crystallographic analysis of the rigid cyclophane-type ligand dd(ip)2 (Br)2 (dd(ip)2 =1,1',3,3'-bis(2,3,5,6-tetramethyl-1,4-phenylene)bis(methylene)bis(1H-imidazo[4,5-f][1,10]phenanthrolinium)) and the catalytic activity of its Ru complex [{(tbbpy)2 Ru}2 (μ-dd(ip)2 )][PF6 ]6 (abbreviated as Ru2 (dd(ip)2 )[PF6 ]6 ) suggest an intermolecular catalytic cycle.

Section: Resultsmentioning

confidence: 97%

“…The two characteristic bands appearing at

\overset{ν}{true}

=1483 and 1540 cm −1 correspond to vibrations located on the tbbpy ligand (highlighted in dark‐grey) . Different bands in the region

\overset{ν}{true}

=1400–1470 cm −1 and at

\overset{ν}{true}

≈1573 cm −1 are seen for all of the ip ligands (highlighted in light‐grey) and show different signatures depending on the degree of substitution by methyl groups.…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 3 more Smart Citations

Oxygen‐Dependent Photocatalytic Water Reduction with a Ruthenium(imidazolium) Chromophore and a Cobaloxime Catalyst

Petermann

Staehle

Pfeifer

et al. 2016

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Merging of a Perylene Moiety Enables a Ru^II Photosensitizer with Long‐Lived Excited States and the Efficient Production of Singlet Oxygen

Schmid

Brückmann

Bösking

et al. 2021

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Multichromophoric systems based on a Ru II polypyridine moiety containing an additional organic chromophore are of increasing interest with respect to different lightdriven applications. Here, we present the synthesis and detailed characterization of a novel Ru II photosensitizer, namely [(tbbpy) 2 Ru((2-(perylen-3-yl)-1H-imidazo[4,5-f][1,10]phenanthrolline))](PF 6 ) 2 RuipPer, that includes a merged perylene dye in the back of the ip ligand. This complex features two emissive excited states as well as a long-lived (8 μs) dark state in acetonitrile solution. Compared to prototype [(bpy) 3 Ru] 2 + -like complexes, a strongly altered absorption (ɛ = 50.3 × 10 3 M À 1 cm À 1 at 467 nm) and emission behavior caused by the introduction of the perylene unit is found. A combination of spectro-electrochemistry and timeresolved spectroscopy was used to elucidate the nature of the excited states. Finally, this photosensitizer was successfully used for the efficient formation of reactive singlet oxygen.

Stereoconvergent Synthesis of Z‐1,3‐Disubstituted‐1,3‐Dienes by Uphill Photocatalysis

Diver

Glickert

Rohde

et al. 2022

A variety of 1-aryl-1,3-dienes were isomerized from E to Z isomers by photocatalysis using Ru(bpy) 3 [PF 6 ] 2 and blue LED light. Enrichment of the Z-isomer is thought to occur by selective triplet energy transfer from the photocatalyst to the stereoisomeric mixture. The 1,3-diene starting materials are easily made by catalytic ene-yne metathesis (EYM). To access 1,3-diene Z-stereoisomers directly, a one pot procedure was developed. Additional 1,3-dienes were investigated for both isomerization and Z-enrichment. The combination of cross EYM with photocatalysis allows for the stereoconvergent synthesis of Z-1,3-dienes.