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An unprecedented intramolecular [4 + 2] tetrazine-olefin cycloaddition with α,β-unsaturated substrates was discovered. The reaction produces unique coumarin-dihydropyridazine heterocycles that exhibited strong fluorescence with large Stokes shifts and excellent photo- and pH-stability. This property can be used for reaction analysis. The rate of cycloaddition was found to be solvent dependent and was determined using experimental data with a kinetic modeling software (COPASI) as well as DFT calculations ( k 1 = 0.64 ± 0.019 s −1 and 4.1 s −1 , respectively). The effects of steric and electronic properties of both the tetrazine and α,β-unsaturated carbonyl on the reaction were studied and followed the known trends characteristic of the intermolecular reaction. Based on these results, we developed a “release-then-click” strategy for the ROS triggered release of methylselenenic acid (MeSeOH) and a fluorescent tracer. This strategy was demonstrated in HeLa cells via fluorescence imaging.

The preparation of a novel H-bonding DBU-H + BINOLate Rare Earth Metal complex enabled the synthesis of the first copper-Rare Earth Metal BINOLate complex (CuDBU-REMB). CuDBU-REMB was compared to the analogous Li complex using X-ray crystallography and Exchange NMR spectroscopy (EXSY). The results provide insight into the role of the secondary metal cation in the framework's stabilization.

Coupled dinuclear copper oxygen cores (Cu₂O₂) featured in type III copper proteins (hemocyanin, tyrosinase, catechol oxidase) are vital for O₂transport and substrate oxidation in many organisms.μ‐1,2‐cisperoxido dicopper cores (^CP) have been proposed as key structures in the early stages of O₂binding in these proteins; their reversible isomerization to other Cu₂O₂cores are directly relevant to enzyme function. Despite the relevance of such species to type III copper proteins and the broader interest in the properties and reactivity of bimetallic^CPcores in biological and synthetic systems, the properties and reactivity of^CPCu₂O₂species remain largely unexplored. Herein, we report the reversible interconversion ofμ‐1,2‐transperoxido (^TP) and^CPdicopper cores. Ca^IImediates this process by reversible binding at the Cu₂O₂core, highlighting the unique capability for metal‐ion binding events to stabilize novel reactive fragments and control O₂activation in biomimetic systems.

Coupled dinuclear copper oxygen cores (Cu₂O₂) featured in type III copper proteins (hemocyanin, tyrosinase, catechol oxidase) are vital for O₂transport and substrate oxidation in many organisms.μ‐1,2‐cisperoxido dicopper cores (^CP) have been proposed as key structures in the early stages of O₂binding in these proteins; their reversible isomerization to other Cu₂O₂cores are directly relevant to enzyme function. Despite the relevance of such species to type III copper proteins and the broader interest in the properties and reactivity of bimetallic^CPcores in biological and synthetic systems, the properties and reactivity of^CPCu₂O₂species remain largely unexplored. Herein, we report the reversible interconversion ofμ‐1,2‐transperoxido (^TP) and^CPdicopper cores. Ca^IImediates this process by reversible binding at the Cu₂O₂core, highlighting the unique capability for metal‐ion binding events to stabilize novel reactive fragments and control O₂activation in biomimetic systems.