Synthesis and O2-binding properties of tetraphenylporphyrinatoiron(II) derivatives bearing a proximal imidazole covalently bound at the β-pyrrolic position

5,10,15,20-Tetrakis(o-pivalamidophenyl)porphyrins (TPVP) and their iron(II) derivatives bearing a proximal imidazole covalently bound at the 2-(β-pyrrolic) position have been synthesized. The visible absorption maxima (λmax) of the 2-substituted TPVP with an electron withdrawing group attached is shifted toward the red region (7–11 nm) compared with that of the original TPVP. The iron(II) complexes having an imidazolyl group at the β-pyrrolic position were five coordinated species with an intramolecularly bound base under argon and reversibly formed a stable dioxygen adduct in response to O2-pressure in toluene at 25 °C. These molecules act as efficient dioxygen carrying molecules. The kinetics of O2 binding to the 2-substituted Fe(TPVP) complexes are described.