Iron TAML activators of peroxides are functional catalase-peroxidase mimics. Switching from hydrogen peroxide (H2O2) to dioxygen (O2) as the primary oxidant was achieved by using a system of reverse micelles of Aerosol OT (AOT) in n-octane. Hydrophilic TAML activators are localized in the aqueous microreactors of reverse micelles where water is present in much lower abundance than in bulk water. n-Octane serves as a proximate reservoir supplying O2 to result in partial oxidation of FeIII to FeIV-containing species, mostly the FeIIIFeIV (major) and FeIVFeIV (minor) dimers which coexist with the FeIII TAML monomeric species. The speciation depends on the pH and the degree of hydration w0, viz., the amount of water in the reverse micelles. The previously unknown FeIIIFeIV dimer has been characterized by UV–vis, EPR, and Mössbauer spectroscopies. Reactive electron donors such as NADH, pinacyanol chloride, and hydroquinone undergo the TAML-catalyzed oxidation by O2. The oxidation of NADH, studied in most detail, is much faster at the lowest degree of hydration w0 (in “drier micelles”) and is accelerated by light through NADH photochemistry. Dyes that are more resistant to oxidation than pinacyanol chloride (Orange II, Safranine O) are not oxidized in the reverse micellar media. Despite the limitation of low reactivity, the new systems highlight an encouraging step in replacing TAML peroxidase-like chemistry with more attractive dioxygen-activation chemistry.

TAML activators enable unprecedented, rapid, ultradilute oxidation catalysis where substrate inhibitions might seem improbable. Nevertheless, while TAML/HO rapidly degrades the drug propranolol, a micropollutant (MP) of broad concern, propranolol is shown to inhibit its own destruction under concentration conditions amenable to kinetics studies ([propranolol] = 50 μM). Substrate inhibition manifests as a decrease in the second-order rate constant k for HO oxidation of the resting Fe-TAML (RC) to the activated catalyst (AC), while the second-order rate constant k for attack of AC on propranolol is unaffected. This kinetics signature has been utilized to develop a general approach for quantifying substrate inhibitions. Fragile adducts [propranolol, TAML] have been isolated and subjected to ESI-MS, florescence, UV-vis, FTIR, H NMR, and IC examination and DFT calculations. Propranolol binds to Fe-TAMLs via combinations of noncovalent hydrophobic, coordinative, hydrogen bonding, and Coulombic interactions. Across four studied TAMLs under like conditions, propranolol reduced k 4-32-fold (pH 7, 25 °C) indicating that substrate inhibition is controllable by TAML design. However, based on the measured k and calculated equilibrium constant K for propranolol-TAML binding, it is possible to project the impact on k of reducing [propranolol] from 50 μM to the ultradilute regime typical of MP contaminated waters (≤2 ppb, ≤7 nM for propranolol) where inhibition nearly vanishes. Projecting from 50 μM to higher concentrations, propranolol completely inhibits its own oxidation before reaching mM concentrations. This study is consistent with prior experimental findings that substrate inhibition does not impede TAML/HO destruction of propranolol in London wastewater while giving a substrate inhibition assessment tool for use in the new field of ultradilute oxidation catalysis.

The extremely persistent molluscicide, metaldehyde, widely used on farms and gardens, is often detected in drinking water sources of various countries at concentrations of regulatory concern. Metaldehyde contamination restricts treatment options. Conventional technologies for remediating dilute organics in drinking water, activated carbon, and ozone, are insufficiently effective against metaldehyde. Some treatment plants have resorted to effective, but more costly UV/H2O2. Here we have examined if TAML/H2O2 can decompose metaldehyde under laboratory conditions to guide development of a better real world option. TAML/H2O2 slowly degrades metaldehyde to acetaldehyde and acetic acid. Nuclear magnetic resonance spectroscopy ((1)H NMR) was used to monitor the degradation-the technique requires a high metaldehyde concentration (60 ppm). Within the pH range of 6.5-9, the reaction rate is greatest at pH 7. Under optimum conditions, one aliquot of TAML 1a (400 nM) catalyzed 5% degradation over 10 h with a turnover number of 40. Five sequential TAML aliquots (2 μM overall) effected a 31% removal over 60 h. TAML/H2O2 degraded metaldehyde steadily over many hours, highlighting an important long-service property. The observation of metaldehyde decomposition under mild conditions provides a further indication that TAML catalysis holds promise for advancing water treatment. These results have turned our attention to more aggressive TAML activators in development, which we expect will advance the observed technical performance.

The efficacy of the iron(III) TAML activator [Fe{C 6 H 4 -1,2-(N 1 COCMe 2 N 2 CO) 2 CMe 2 (Fe−N 1 )(Fe−N 2 )}(OH 2 )] − (1) for the catalytic activation of dioxygen in reverse micelles of Aerosol OT (AOT) in n-octane has been studied. Kinetic evidence is presented for the existence of unusual second-order catalytic pathways in the oxidation of NADH to NAD + and the bleaching of blue pinacyanol chloride (PNC) dye. Depending on the substrate and reaction conditions, a second-order pathway in [1] either dominates or proceeds in obvious combination with a first-order pathway in [1]. Detailed kinetic analysis of the experimental data supports the previously made hypothesis that the reactive intermediate is associated with the mixedvalent dimer system [LFe III OFe IV L] 3− /[LFe III (OH)Fe IV L] 2− .

An electrochemically oxidative domino cyclization reaction of methyl azaarenes/ketones with pyrazol-5-amines and 6-amino-pyrimidine-2,4-diones was developed, providing a variety of dipyrazolo[3,4-b:4',3'-e]pyridines and dipyrimidine-fused pyridines with moderate to good yields. The reaction...