A tris(pyrazolyl)-based model for the aminocyclopropane carboxylic acid oxidase and its behavior towards oxidants.

A low-molecular-weight analog of the 1-aminocyclopropane carboxylic acid oxidase (ACCO), [TpFeACC], 1, where the (His₂Asp)iron(II) moiety is mimicked by a hydrotris(3-mesitylpyrazol-1-yl)borato iron(II) unit, to which the natural substrate aminocyclopropane carboxylate is coordinated, has been accessed and structurally characterized. It was found to react slowly with O to yield the biological product ethylene. To create models of the intermediates proposed as part of the catalytic cycle of the ACCO 1 was treated with tBuOOH and mCPBA at low temperatures, which generated the respective FeOOtBu and Fe=O intermediates as shown by spectroscopic analysis. Studies on their behavior upon annealing reveal a non-biomimetic reactivity.