We systematically investigated the reversibility, time lapse, and oxygenation-deoxygenation properties of 15 naturalα-amino acid–Co(II) complexes through UV-vis spectrophotometer, polarographic oxygen electrode, and DFT calculations, respectively, to explore the relationship between the coordinating structure and reversible oxygenation ofα-amino acid–Co(II) complexes. Results revealed that theα-amino acid structure plays a key role in the reversible oxygenation properties of these complexes. The specific configuration of theα-amino acid group affects theeg1electron of Co(II) transfer to theπ⁎orbit of O 2 ; this phenomenon also favors the reversible formation and dissociation of Co–O 2 bond when O 2 coordinates with Co(II) complexes. Therefore, the co-coordination of amino and carboxyl groups is a determinant of Co complexes to absorb O 2 reversibly. The group adjacent to theα-amino acid unit evidently influences the dioxygen affinity and antioxidation ability of the complexes. The presence of amino (or imino) and hydroxy groups adjacent to theα-amino acid group increases the oxygenation-deoxygenation rate and the number of reversible cycles. Our findings demonstrate a new mechanism to develop reversible oxygenation complexes and to reveal the oxygenation of oxygen carriers.

Xincun Zhang

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