A combined photokinetical approach helped develop and optimize a green-light driven photoredox catalytic system that generates a “super-reductant” with simple instrumentation, consumes only a bioavailable donor, and provides very high turnover numbers.

We present the first working system for accessing and utilizing laboratory-scale concentrations of hydrated electrons by photoredox catalysis with a green light-emitting diode (LED). Decisive are micellar compartmentalization and photon pooling in an intermediate that decays with second-order kinetics. The only consumable is the nontoxic and bioavailable vitamin C. A turnover number of 1380 shows the LED method to be on par with electron generation by high-power pulsed lasers, but at a fraction of the cost. The extreme reducing power of the electron and its long unquenched life as a ground-state species are synergistic. We demonstrate the applicability to the dechlorination, defluorination, and hydrogenation of compounds that are inert towards all other visible-light photoredox catalysts known to date. A comprehensive mechanistic investigation from microseconds to hours yields results of general validity for photoredox catalysis with photon pooling, allowing optimization and upscaling.

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Hydrated electrons are highly aggressive species that can force chemical transformations of otherwise unreactive molecules such as the reductive detoxification of halogenated organic compounds. We present the first example of the sustainable production of hydrated electrons through a homogeneous catalytic cycle driven entirely by green light (532 nm, coinciding with the maximum of the terrestrial solar spectrum). The catalyst is a metal complex serving as a "container" for a radical anion. This active center is generated from a ligand through quenching by a sacrificial electron donor, is shielded by the complex such that it stores the energy of the photon for much longer than a free radical anion could, and is finally ionized by another photon to regenerate the ligand and recover the starting complex quantitatively. The sacrificial donor can be a bioavailable reagent such as ascorbic acid.

Incidental predation occurs when secondary prey items are encountered and subsequently consumed, not through directed search for such prey, but through their consequential encounter by a predator engaged in search for primary prey. We developed a mathematical model that examines the relationships between the abundance of primary prey, patch exploitation (i.e., quitting harvest rates), and the rate of incidental predation on secondary prey items. The model's predictions are dependent upon the spatial scale over which a forager integrates foraging costs and thus determines its quitting harvest rate (QHR). At local (i.e., foraging) spatial scales, we predicted that incidental predation should increase with local food abundance. Also at the foraging scale, local food abundance should not influence QHRs, but local predation risk (from higher trophic levels) should increase QHRs. Therefore, we predicted that incidental predation rates should be negatively correlated with QHRs. Over large (i.e., landscape) spatial scales, greater food abundance and predation risk increase QHRs, and we predicted that predation rates should vary inversely with QHR through two complementary mechanisms: foragers use a greater proportion of space and spend more time foraging as quitting harvest rates decrease.We experimentally tested the qualitative predictions of the theory in the field using artificial Veery (Catharus fuscescens) nests depredated by white-footed mice, Peromyscus leucopus, across three spatial scales. We used the technique of giving-up densities to measure QHRs and to determine the scale at which mice integrate different foraging costs. In accord with our predictions, nest predation was positively influenced by the local abundance of food at the foraging scale, and local predation risk to mice and perhaps interference competition from chipmunks resulted in higher giving-up densities and lower nest predation. At the landscape scale, there was an inverse relationship between giving-up densities and nest predation, which was probably the result of large-scale differences in resource abundance between plots. Our study demonstrates how linking theoretical development to the use of empirical behavioral indicators can help determine the relevant ecological scales and processes necessary for understanding predator-prey interactions.

The discovery of the highly NIR-luminescent Molecular Ruby [Cr(ddpd)2]3+ 13+ (ddpd = N,N’-dimethyl-N,N’-dipyridine-2-ylpyridine-2,6-diamine) has been a milestone in the development of earth-abundant luminophors and has led to important new impulses...

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The hydrated electron represents a "super-reductant" in water, providing 2.9 eV of reductive power, which suffices to decompose nonactivated aliphatic halides. We show that 3-amino-perylene in SDS micelles, when combined with the bioavailable ascorbate as an extramicellar sacrificial donor, sustainably produces hydrated electrons through photoredox catalysis with green light, from a metal-free system, and at near-physiological pH. Photoionization of the amine with a 532 nm laser yields an extremely long-lived radical cation as the by-product, and a subsequent reaction of the latter with the sacrificial donor across the micelle/water interface regenerates the catalyst. The regeneration step involves parallel reactions between differently protonated forms, causing a bell-shaped pH dependence in basic medium. We have separated these processes kinetically. Employing this catalytic cycle for the laboratory-scale decomposition of chloroacetate, an accepted model compound for toxic and persistent halo-organic waste, gave turnover numbers of about 170. Even though both the substrate and the sacrificial donor compete for the hydrated electron, their consumption ratio is practically independent of the initial concentration ratio because the formal radical anion of the ascorbate undergoes secondary scavenging by the chloroacetate. In the course of the reaction, the initial hydrophobic catalyst is converted into a secondary species that is hydrophilic and still exhibits catalytic activity.