Analytical Sciences

Complex Formation of p-Nitrocalix[6]arene with Rare Earth Metal Ions

Makiko KAJIWARA, Masayoshi KOGA, Masashi NISHIDA, and Isao YOSHIDA

Department of Applied Chemistry, Faculty of Engineering, Sojo University, 4-22-1 Ikeda, Kumamoto 860-0082, Japan

p-Nitrocalix[6]arene (CALX-N6, L) formed a 1:1 metal complex, ML, with light rare earth metal ions (M³⁺), such as La³⁺, Pr³⁺ and Nd³⁺ except Ce³⁺, but formed a 1:2 (M³⁺:L) complex, ML₂ (the charge of the complex is omitted) with heavy rare earth metal ions, such as Sm³⁺-Lu³⁺ including Y³⁺. The conditional stability constants of these 1:1 and 1:2 complexes, K_ML and K_ML2, were measured by a ligand displacement method using absorption spectrophotometry in 4% (v/v) acetone aqueous solution at pH 9.65 ± 0.15 and 25°C.

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