Transient spectroscopy sheds light on elusive photoredox process

Researchers have provided spectroscopic evidence for the mechanism of a two-photon photoredox process known as sensitisation-initiated electron transfer, or SenI-ET. They applied transient absorption and emission spectroscopy to an iridium-based photosensitiser–catalyst couple, which allowed them to identify the active catalytic species – a short-lived pyrenyl radical anion – for the first time. The researchers hope their work will inform the design of new photoredox systems based on multi-photon excitation, with potential applications in synthetic organic photochemistry and solar fuel conversion.