Correlation of the Chemical Reactivity of Some Tetrazine Derivatives with Their Reactivity toward Ortho-positronium Atoms and Their LUMO Energies, András Kotschy, Zoltán Novák, Béla Lévay, J. Phys. Chem. A 2004, 108, 1753-1756. DOI: 10.1021/jp0373649 | [Full Text Link]
Chemical reaction rate constants of the nucleophilic ortho-positronium (o-Ps) atom with a series of tetrazine derivatives were determined in dimethylformamide (DMF) solutions by positron annihilation lifetime spectroscopy. The observed rate constants are in the range that corresponds to that of the diffusion-controlled reactions. It was shown that this pronounced reactivity of tetrazines toward o-Ps stems from the electron-deficient tetrazine core. The introduction of electron-donating substituents onto the tetrazine ring, as expected, decreases the reactivity of the molecule toward o-Ps. The measured reaction rate constants of o-Ps resulted in a good linear correlation with the calculated LUMO energies of the tetrazines. The reactivity of tetrazines toward o-Ps correlated well also with their reactivity toward classical nucleophiles.