Identification of Derivatives of Cobalt-binding BLM-A2 by NMR

Abstract

Three different derivatives were obtained in the synthesis of cobalt- binding BLM-A2 and characterized by NMR and Mass spectrometry. It was found that Component 1 is Co(II)(2H2O)(BLM-A2), component 2 is Co(III)(OOH-)(BLM- A2) and component 3 is Co(III)(H2O)(OH-)(BLM-A2), respectively. Component 2 and 3 were interestingly dominated when CoBLM-A2 complex was synthesized under basic condition. In this experiment, it was revealed newly that the brown form (component 1) was 6-oordinated structure composed with not 5 ligands but 4 ligands from BLM-A2 and with 2H2O as the axial ligands. The component 3 exhibiting a novel ligand configuration is found, and the structure of component 3 was observed to be very similar to that of component 1 in the kind of their ligands but one of the axial ligand is OHinstead of H2O. These ligand configurations are different from the green form (component 2) exhibiting 6-coordinate structure composed of 5 ligands from BLM-A2 and one ligand of OOH- , being consistent with former studies.