The structure of the monomeric oxygen adduct of vitamin B12r: A single crystal ESR study

From ESR single crystal spectra of B_12rO₂ substituted in B_12b the structure of the CoOO fragment was determined at ?190°C. The g and A^Co tensors were found to be non-coaxial with the following principal values: g₁ = 1.994,g₂ = 2.012, g₃ = 2.079; A^Co₁ = ?21 MHz, A^Co₂ = ?27 MHz, A^Co₃ = ?63 MHz. The CoOO bond angle is 111°.