Beyond Mimicking Enzymes: NewTAML/Peroxide Abstracts sp ³ C–H Bonds to Initiate Biotranscendent Water-Purifying Mineralization of Fluoroquinolone Antibiotics

In neutral aqueous media under ambient temperature, the bis-amido-bis-sulfonamido-ligated [Fe^III{4-NO₂C₆H₃-1,2-(<i>N</i>COCMe₂<i>N</i>SO₂)₂CHMe}(OH₂)]^- NewTAML catalyst (<b>2</b>), activates hydrogen peroxide to mimic and greatly surpass enzymatic activity (biotranscendence) by sweeping fluoroquinolone antibiotics rapidly toward minerals. Stepwise identification of intermediates was paired with mechanistic examination of key steps. For ofloxacin, the <b>2</b>/H₂O₂ activated catalyst (AC) first attacks ofloxacin's piperazine unit in two enzyme-mimicking parallel pathways, cleaving secondary (desaturation) and primary (<i>N</i>-demethylation) sp³ C-H bonds via H atom abstraction to form dehydro- and desmethyl-ofloxacin, respectively; desaturation is a novel expression of TAML peroxidase-like reactivity. Kinetic data obtained with selectively deuterated ofloxacin compounds revealed for desaturation and <i>N</i>-demethylation, respectively, kinetic isotope effects (<i>k</i>_H/<i>k</i>_D) of 8.6 and 3.8; Δ<i>H</i>^‡ and Δ<i>S</i>^‡ are presented. Dehydro- and desmethyl-ofloxacin are further oxidized through several identified intermediates toward minerals; ion chromatography revealed F^-, CH₃COO^-, HCOO^-, NO₂^-, and NO₃^- as final products. <b>2</b>/H₂O₂ similarly oxidizes ciprofloxacin and norfloxacin. Desaturation by <b>2</b>/H₂O₂ of 1-methyl-4-phenylpiperazine delivered a rate that is comprehensibly half that of ofloxacin. DFT calculations provided compelling evidence that the <b>2</b>/H₂O₂ effective AC is oxidized by two-electrons above the ferric state producing ofloxacin desaturation via sequential hydrogen atom abstraction, single electron transfer and hydrolysis events. Iron(IV) compounds, once considered plausible as ACs in TAML/peroxide C-H bond activations, cannot oxidize ofloxacin sp³ C-H bonds. The temporal toxicity profile of ofloxacin's degradation intermediates based on <i>in silico</i> toxicities highlights that <b>2</b>/H₂O₂ can serve as a powerful <i>safe-and-sustainable-by-design</i> (SSbD) fluoroquinolone detoxifying water treatment.