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Expanding Thermodynamic and Kinetic Frontiers in Molecular Photocatalysis Extreme redox potentials, solvated electrons, upconversion, ultrafast photo-dissociation, slow uphill reactions and beyond @pubs.acs.org pubs.acs.org/doi/10.1021/...

Visible photons carry significantly more energy than the thermal energies typically used to overcome activation barriers in conventional chemistry. This thermodynamic advantage enables photochemical reactions that are inaccessible from electronic ground states. However, photochemistry also faces a kinetic challenge: excited states are inherently short-lived, necessitating rapid reactivity before their decay. In this Outlook, we explore the unique interplay of thermodynamics and kinetics in molecular photochemistry. We highlight current limits and knowledge gaps and propose directions for advancing the conceptual framework of photocatalysis. Topics include the design of photocatalysts with extreme redox potentials, the use of solvated electrons and visible-to-UV upconversion, and the potential to bypass Kasha’s rule for higher-energy photochemical processes. Our aim is to survey strategies for pushing the boundaries of photocatalysis and to inspire future conceptual innovation in the field.

Excited to share another first-author paper from Pengyue Jin: Beyond the Diffusion Limit: Preassociation Enhanced Photon Upconversion and Photocatalysis Sensitized by Iron Complex | ACS Catalysis Great thanks to the @dfg.de for the funding! pubs.acs.org/doi/full/10....

Finally out! Very happy about this work with Alok Mahata, Biprajit Sarkar et al.!! #chemsky #science #compchem Stimuli-Responsive Thiele’s Hydrocarbon Derivatives: Potential Inversion, Strong Electronic Coupling, and Influence of Brønsted/Lewis Acids and Bases | JACS Au pubs.acs.org/doi/10.1021/...

Happy to share this amazing work from Dilara @univie.ac.at, together with Dwyne Miller‘s group @utoronto.ca, just out at @angewandtechemie.bsky.social 🔥🔥🔥🔥🔥 #SHARC 🦈 SCO dynamics with #RASSCF in a Fe(III) open-shell complex & transient spectroscopy 🧪⌨️💡 onlinelibrary.wiley.com/doi/10.1002/...

2026 marks 90 years of [Ru(bpy)₃]²⁺ which has undoubtedly shaped photochemistry since its inception. Celine Bourgois, @ludotroian.bsky.social and I took this opportunity to examine how this old system continues to fuel innovation in the field. Check it out here: pubs.acs.org/doi/10.1021/...

➡️ Increasing the length of molecular nanographenes leads to higher photoluminescence quantum yields!💡 In this @jacs.acspublications.org paper, we show how molecular length tunes the interplay between dark and bright excited states. 🔗 pubs.acs.org/doi/10.1021/... Many thanks to all coauthors!!

Red-Light Photoredox C–H Alkylation Enabled by Catalytic NADH, now out in @chemrxivbot.bsky.social chemrxiv.org/doi/full/10.... From synthetic application to TAS mechanistic understanding, passing through radical biocompatibility. Awesome collab @ciqus.bsky.social and @cadralab.bsky.social

Ultrafast broadband transient absorption spectroscopy and multireference excited-state nonadiabatic calculations in an open-shell Fe(III) complex unveil the rich electronic and vibrational dynamics d...

Photoactive iron complexes present highly desirable and accessible alternatives to the well-known noble metal complex-based photocatalysts, thanks to iron’s high abundance, low toxicity, and minimal e...

Stimuli-responsive diradicaloid systems often display fascinating and tunable electrochemical, optical, and magnetic properties. Herein, we present the design and synthesis of a series of nitrogen-con...

Nanographenes (NGs) and graphene nanoribbons (GNRs) are molecular-level bridges to bulk-carbon materials. When synthesized with atomic precision via, for example, bottom-up strategies, a direct connection between the structure and properties is demonstrable. This is of key interest, especially considering practical applications. In the current work, we report the synthesis and comprehensive photophysical characterization of a full-benzenoid nanographene (NG-Br) and its covalent conjugate featuring a porphyrin (NG-(Zn)Por). Our synthetic approach relies on a cascade of Suzuki coupling, reduction, and Sandmeyer bromination reactions, starting from halogenated nitrobenzene derivatives. Knowing at which concentration aggregation occurs is important to study either monomers of NG-Br or its aggregates. In organic solvents, the association constant of NG-Br exceeds 1 × 106 M–1. Photophysical and theoretical analyses on the monomer revealed a subtle energy proximity between (S1)/(Lb) and (S2)/(La) that is the basis for strong vibronic coupling via the Herzberg–Teller mechanism, as well as (S1,1) and (S2,0) vibronic mixing. In NG-(Zn)Por, an ultrafast (S1–S1) energy transfer from NG to the porphyrin was observed. Our findings are essential for establishing an unambiguous structure–property relationship for NGs and 9-armchair GNRs, providing a blueprint for their use in optoelectronic devices ranging from single-electron transistors to OLEDs and organic solar cells.

Singlet fission (SF), a photophysical process generating two triplet excitons from one singlet exciton, has the potential to boost efficiency in photovoltaics and organic light-emitting diodes. Previous studies on energy-level control and intermolecular interactions have identified key factors for maximizing the efficiency of the initial SF process. However, in isothermic/endothermic SF systems, such as tetracene derivatives, the subsequent sensitization process becomes less efficient in the presence of a competing Förster resonance energy transfer (FRET) process. Here, we demonstrate that a molybdenum-based near-infrared light-emitting spin-flip emitter serves as a triplet-selective energy acceptor from triplet states of tetracene-based dimers generated by SF. The large energy gap existing between the spin-allowed transitions and the luminescent spin-flip transition of the molybdenum complex allowed efficient exothermic triplet energy transfer (TET) to the spin-flip excited doublet state of the complex while circumventing the FRET from the initially formed tetracene singlet state to the high-energy spin-allowed states of the complex. The quantum yields of the doublet state formation of the molybdenum complex by tetracene-based SF dimers with phenylene, 2,5-methylphenylene, and p-terphenylene bridging units were quantified to be 112 ± 6%, 132 ± 2%, and 128 ± 4%, respectively, in solution. The drop of fluorescence lifetimes of the SF dimers at high concentrations of the molybdenum complex implies energy transfer from exchange-coupled triplet pairs, highlighting the importance of controlling exchange interaction and triplet pair recombination. This work represents a significant step toward developing exciton/photon amplification materials by combining SF materials with transition-metal complexes, advancing the application of SF beyond conventional limitations.

Matthias' paper with a thorough investigation of a Coulombic Dyad has been published in Chem. Phys. Rev. as a part of the "70 Years of Dexter Energy Transfer" collection. Many thanks also to our collaborators from the @labheinze.bsky.social and Diezemann groups). #Photochemistry #EnergyTransfer