Dicationic Acridinium/Carbene Hybrids as Strongly Oxidizing Photocatalysts

14 November 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


A new design concept for organic, strongly oxidizing photocatalysts is described based upon dicationic acridinium/carbene hybrids. A highly modular synthesis of such hybrids is presented and the dications are utilized as novel, tailor-made photoredox catalysts in the direct oxidative C−N coupling. Under optimized conditions, benzene and even electron-deficient arenes can be oxidized and coupled with a range of N-heterocycles in high to excellent yields with a single low-energy photon per catalytic turnover, while commonly used acridinium photocatalysts are not able to perform the challenging oxidation step. In contrast to traditional photocatalysts, the here reported hybrid photocatalysts feature a reversible two-electron redox system with regular or inverted redox potentials for the two-electron transfer. The different oxidation states could be isolated and structurally characterized supported by NMR, EPR and X-ray analysis. Mechanistic experiments employing time-resolved emission and transient absorption spectroscopy unambiguously reveal the outstanding excited-state oxidation potential of our best-performing catalyst (+2.5 V vs. SCE) and they provide evidence for mechanistic key steps and intermediates.


Oxidative photocatalysis
arene oxidation
organic redox-systems

Supplementary materials

Supporting Information
Contains Supporting Information


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