Peripheral ligands as electron storage reservoirs and their role in enhancement of photocatalytic hydrogen generation

Abstract

The contrasting early-time photodynamics of two related Ru/Pt photocatalysts with very different photocatalytic H2 generation capabilities are reported. Ultrafast equilibration (535 ± 17 fs) creates an electron reservoir on the peripheral ligands of the ester substituted complex, allowing a dramatic increase in photocatalytic performance. This insight opens the way towards a novel design strategy for H2 generating molecular photocatalysts.

Enhancing Photocatalytic Hydrogen Generation: the Impact of the Peripheral Ligands in Ru/Pd and Ru/Pt Complexes

“…However, emission data indicate that the emission decays are different for palladium‐ and platinum‐containing complexes, and hence the electron flows in those complexes are also different. In an earlier study, transient‐absorption measurements indicated that the dceb ligands most likely act as an electron store, which is contrary to the traditional assumption that electron density is stored on the bridging ligand . The present contribution supports this perception, based on the obtained experimental and DFT data.…”

“…The complexes reported in this contribution are part of a larger investigation of Ru/Pd and Ru/Pt dyads with various bridging (see Figure ) and peripheral ligands performed by our group under the same experimental conditions . As was observed for the compounds investigated in this contribution, the catalytic activity of these dyads in hydrogen evolution was dependent on changes to the bridging or the peripheral ligands.…”

“…We report the synthesis and characterisation of novel intramolecular Ru/Pd and Ru/Pt complexes tethered by a bisbpy bridging ligand. This work is part of a series of systematic studies to investigate the influence of the bridging ligand, peripheral ligands and nature of the catalytic centres on light‐driven hydrogen generation . The most‐striking observation from the present investigation is that greatly increased TON are obtained when peripheral dceb ligands are introduced, irrespective of the nature of the bridging ligand or catalytic centre.…”

“…Recently we studied photocatalysts that contained the 2,5‐bpp ligand . In this contribution we extended our studies to include the bisbpy bridging ligand.…”

A Heterobimetallic AuIII‐PtII Photocatalyst for Water Reduction to Hydrogen

“…However, complex 1 exhibited rather low TON compared to many other supramolecule catalysts, probably due to its shorter emission lifetime. According to the relative reports, the excited state lifetimes of reported bimetallic complexes are usually multiples even ten times of that of 1 , enabling the proceeding of the slow photochemical processes . Additionally, the quenching constant ( k q ) of 1 is about one or two orders of magnitude lower than other systems, indicating some of the difficulties of electron transfer between 1 and sacrificial agent.…”