High turnover photocatalytic hydrogen formation with an Fe(iii) N-heterocyclic carbene photosensitiser

Abstract

The first high turnover photocatalytic hydrogen formation reaction using an earth-abundant iron photosensitiser is presented.

Simultaneous non-invasive gas analysis in artificial photosynthesis reactions using rotational Raman spectroscopy

“…This can primarily be attributed to two of its inherent advantages, as was shown in the recent development of an HER using an iron PS in combination with different proton reduction catalysts. 24 There, a measurement time of 25 s was used and three replicates were recorded, resulting in a total measurement time of less than 1.5 min per sample, while obtaining reliable data for each measurement (RSD ¼ 1%). As a result of the short analysis time, the main factor limiting the number of reactions performed and tracked in parallel when choosing not to trace in situ is the irradiation set-up itself, wherein only a certain number of reaction vials can be irradiated simultaneously, and not the analysis method.…”

Photoredox catalysis via consecutive 2LMCT- and 3MLCT-excitation of an Fe(iii/ii)–N-heterocyclic carbene complex

“…Transient absorption spectroscopy furthermore confirmed that the quenching occurs by reductive electron transfer producing stable 2 (Figure 4) with a quantum yield hqhce of about 9 % (Table S16). Notably, the lower yield of quenching implied by the short lifetime is balanced by a cage escape yield hce > 20 % that largely exceeds the very moderate values previously found for the quenching of the 2 LMCT state of [Fe(III)(phtmeimb)2] + in acetonitrile 30,37 . PS (t0 /ps)…”

“…Notably, the lower yield of quenching implied by the short lifetime is balanced by a cage escape yield η ce > 20% that largely exceeds the very moderate values previously found for the quenching of the 2 LMCT state of [Fe( iii )(phtmeimb) 2 ] + in acetonitrile. 30,37…”

“…Notably, the lower yield of quenching implied by the short lifetime is balanced by a cage escape yield h ce > 20% that largely exceeds the very moderate values previously found for the quenching of the 2 LMCT state of [Fe(III)(phtmeimb) 2 ] + in acetonitrile. 30,37 In case of conventional single-photon excitation-based photoredox catalysis, the reduction of C 8 F 17 I by 2 would constitute the next step in the mechanism, regenerating the GS of 1 and initiating the ATRA reaction. In our case, the reduced PC 2 is evidently not sufficiently reducing (À0.58 V vs. Fc) 36 state of 1 (À1.0 V vs. Fc).…”

“…32,33 These photocatalytic reactions were enabled by the emergence of Fe-NHC-complexes 29,[34][35][36] (NHC ¼ N-heterocyclic carbene) with excited state lifetimes approaching and exceeding the nanosecond threshold, which has brought forth the rst examples of intermolecular ES quenching of CT states in an iron PS, [Fe(phtmeimb) 2 ]PF 6 (phtmeimb ¼ tris(3-methylimidazolin-2-ylidene)(phenyl)borate). 29,30,37 The possibility for their application was recently further explored by Aydogan et al, 32,33 where sizeable cage escape yields (CEYs) and corresponding quantum efficiencies with common trialkylamine donors were observed. However, these comparatively high CEYs were dependant on the use of halogenated solvents, thereby potentially restricting the scope of possible applications.…”