Iron(V)-oxo species have been proposed as key reactive intermediates in the catalysis of oxygen-activating enzymes and synthetic catalysts. Here, we report the synthesis of [Fe(TAML)(O)]- in nearly quantitative yield, where TAML is a macrocyclic tetraamide ligand. Mass spectrometry, Mössbauer, electron paramagnetic resonance, and x-ray absorption spectroscopies, as well as reactivity studies and density functional theory calculations show that this long-lived (hours at -60 degrees C) intermediate is a spin S = 1/2 iron(V)-oxo complex. Iron-TAML systems have proven to be efficient catalysts in the decomposition of numerous pollutants by hydrogen peroxide, and the species we characterized is a likely reactive intermediate in these reactions.

The structurally regular and stable self-assembled capsids derived from viruses can be used as scaffolds for the display of multiple copies of cell- and tissue-targeting molecules and therapeutic agents in a convenient and well-defined manner. The human iron-transfer protein transferrin, a high affinity ligand for receptors upregulated in a variety of cancers, has been arrayed on the exterior surface of the protein capsid of bacteriophage Qβ. Selective oxidation of the sialic acid residues on the glycan chains of transferrin was followed by introduction of a terminal alkyne functionality via an oxime linkage. Attachment of the protein to azide-functionalized Qb capsid particles in an orientation allowing access to the receptor binding site was accomplished by the CuI-catalyzed azide-alkyne cycloaddition (CuAAC) click reaction. Transferrin conjugation to Qβ particles allowed specific recognition by transferrin receptors and cellular internalization via clathrin-mediated endocytosis, as determined by fluorescence microscopy on cells expressing GFP-labeled clathrin light chains. By testing Qβ particles bearing different numbers of transferrin molecules, it was demonstrated that cellular uptake was proportional to ligand density, but that internalization was inhibited by equivalent concentrations of free transferrin. These results suggest that cell targeting with transferrin can be improved by local concentration (avidity) effects.

A Fe-TAML/H2O2 catalytic oxidation process achieves facile in-solution total degradation of fenitrothion and two other organophosphorus (OP) pesticides. Degradation products have been identified and quantified providing evidence for oxidative hydrolysis, oxidative desulfuration, perhydrolysis, and deep oxidation. Degradation pathways can be selected by pH control to completely obviate all toxic residuals. Aquatic toxicity assays support the environmental compatibility of the degradation process.

A view to a kill: Iron(III)‐coordinated tetraamide macrocyclic ligands (see example) activate peroxides in water in the presence of a cationic surfactant to rapidly deactivate spores of the common anthrax surrogate, Bacillus atrophaeus. A 99.99999 % kill can be achieved in 15 min at pH 10 and room temperature with tert‐butyl hydroperoxide (see TEM images).