Controlling Excited-State Reactivity of Iron(III) photosensitizers

Due to its high abundance, low cost and low toxicity, photosensitizers based on iron have long been considered as the holy grail for photochemical applications. Unfortunately, with a few exceptions,[1-3] these photosensitizers suffer from extremely short, sub-nanosecond, excited-state lifetimes that limit diffusional reactivity. We have determined key parameters that have allowed to circumvent these limitations and achieve efficient excited-state electron transfer with large cage-escape yields using green light irradiation.[4,5] Dehalogenation reactions operated with large yields and a clear view of the mechanistic pathway with the associated rate constants was obtained by a combination of time-resolved spectroscopic methods, such as femtosecond and nanosecond transient absorption or infrared spectroscopy (TRIR)

Layer-by-Layer Assembly of Molecular Photoelectrodes on Conductive Metal Oxide for Water Splitting

Layer-by-Layer Assembly of Molecular Photoelectrodes on Conductive Metal Oxide for Water Splittin

Photocatalyzed Dehalogenation Using Iron(III) Photosensitizers

Due to its high abundance, low cost and low toxicity, photosensitizers based on iron have long been considered as the holy grail for photochemical applications. Unfortunately, with a few exceptions, these photosensitizers suffer from extremely short, sub-nanosecond, excited-state lifetimes that limit diffusional reactivity. We have determined key parameters that have allowed to circumvent these limitations and achieve efficient excited-state electron transfer with large cage-escape yields using green light irradiation. Dehalogenation reactions operated with large yields and a clear view of the mechanistic pathway with the associated rate constants was obtained by a combination of time-resolved spectroscopic methods, such as femtosecond and nanosecond transient absorption or infrared spectroscopy (TRIR)

Homogeneous Photocatalytic Systems – Photocatalytic Hydrogen Production

Homogeneous Photocatalytic Systems – Photocatalytic Hydrogen Productio

Four-Membered Rings With Two Heteroatoms Including Silicon to Lead

The field of four-membered rings that contain two heteroatoms of group 14 including silicon to lead has experienced a drastic evolution in the past decade. This was made possible, in particular through the stabilization of heavier alkyne analogs, Ar–Etriple bondE–Ar (E = Ge, Sn or Pb) that served as synthetic precursors for the corresponding four-membered rings. Synthetic progresses, mechanisms, structural properties and theoretical considerations are presented in this article that covers the breakthroughs published between 2007 and 2019, while also including some relevant prior literature

Controlling Excited-State Reactivity Towards More Efficient Energy Conversion

Solar energy represents a promising renewable energy source. In natural and artificial photosynthesis, light absorption and catalysis are separate processes linked together by exergonic electron transfer. There is a plethora of organic transformations that can be sensitized to visible light, but the corresponding reaction mechanisms are not always straightforward. Here, we will present recent advances in the field of mechanistic photoredox catalysis by means of steady-state and time-resolved spectroscopies. A special emphasis will be placed on cage-escape yields, i.e. the efficiency with which the radicals formed after excited-state electron transfer separate and escape the solvent cage. To do that, we have used a series of rare earth and earth abundant photosensitizers that were engaged in either oxidative or reductive excited-state electron transfer processes. Cage-escape could be modulated and is some case were shown to increase when the driving force for photo-induced electron transfer increased

Visible-Light Mediated Reactivity in Solution and at the Metal Oxide Interface for Solar Fuels Production and Catalysis

Visible-Light Mediated Reactivity in Solution and at the Metal Oxide Interface for Solar Fuels Production and Catalysi

Photo-CIDNP reveals two different photo-induced electron/proton transfer processes for protonatable ruthenium(II) polyazaaromatic complexes

Photo-CIDNP reveals two different photo-induced electron/proton transfer processes for protonatable ruthenium(II) polyazaaromatic complexe

Synthesis of polyazaaromatic ligands with extended aromaticity for the development of novel transition metal complexes

Synthesis of polyazaaromatic ligands with extended aromaticity for the development of novel transition metal complexe

Electron photo-accumulation in Ir(III) photosensitizers for proton and CO2 reduction

In view of developing novel sustainable energy supply as an alternative or complement to fossil fuels, different technologies have been explored for the conversion of sunlight into useful energy sources. Among them, the sunlight-triggered hydrogen evolution reaction (HER) represents a promising solution to worldwide consumption of fossil fuels as hydrogen is an energy-dense and carbon-free fuel. This HER usually operates via a photoinduced electron transfer (PET) from a photosensitizer (PS) to a catalytic centre, where hydrogen is produced. Current challenges in the field are related to the development of more robust hydrogen evolving catalysts and photosensitizers that absorb a wider range of the solar spectrum as well as a deeper engagement of researchers towards the development of active repair strategies. In here, we focused on the development of novel Ir(III) photosensitizers that are capable of storing multiple electrons on one ligand for catalysis applications. These novel photosensitizers were evaluated for proton reduction and CO2 reduction using well-established catalysts and compared our results to prototypical iridium(III) photosensitizers unable to photo-accumulate electrons. These results were complemented by nanosecond transient absorption experiments as well as pump-pump-probe experiments