Metal-containing ionic liquids (MCILs) composed of a cobalt(II) Schiff base complex and ionic-liquid-based axial ligands (ligand ILs) are potential O₂ absorbents. To determine the design criteria of MCILs with both highly selective O₂ absorbability and low viscosity, the relationship between the physicochemical properties and chemical structure of the MCILs was investigated. The measurement of the amount of O₂ absorbed in MCILs with various ligand ILs indicated that O₂ reactivity is determined by the electron density of the Co atom of the MCILs. The electron density of the Co atom could be controlled by the σ electron donation ability of the ligand ILs. Moreover, the viscosity of the MCILs was strongly affected by the interaction among the MCIL molecules caused by the π electron system. This interaction was weakened by the equatorially coordinating Schiff base and the ligand ILs within the chemical structure. Therefore, to develop MCILs with both high O₂ reactivity and low viscosity, suppression of the interaction caused by the π electron system without decreasing the electron density of the Co atom is important.

由钴（II）席夫碱配合物和基于离子液体的轴向配体（配体IL）组成的含金属离子液体（MCIL）是潜在的O ₂吸收剂。为了确定具有高选择性O ₂吸收性和低粘度的MCIL的设计标准，研究了MCIL的理化性质与化学结构之间的关系。对具有各种配体IL的MCIL中吸收的O ₂量的测量表明，O ₂反应性由MCIL的Co原子的电子密度决定。Co原子的电子密度可以通过配体IL的σ电子给定能力来控制。此外，由π电子系统引起的MCIL分子之间的相互作用强烈影响MCIL的粘度。赤道配位的席夫碱和化学结构内的配体IL削弱了这种相互作用。因此，为了开发具有高O ₂反应性和低粘度的MCIL，重要的是在不降低Co原子的电子密度的情况下抑制由π电子系统引起的相互作用。