Synthesis and equilibrium study of nickel(II), copper(II), and zinc(II) complexes with N,N¡ä,N¡å,N¡å¡ä,N¡å¡å,N¡å¡å¡ä-hexakis(2-aminoethyl)-1,4,7,10,13,16-hexaazacyclooctadecane in an aqueous solution

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• 作者：Tsutomu Kurisaki ; Yuichi Matsuki ; Hisanobu Wakita
• 关键词：Macrocyclic polyamines ; Formation constant ; Transition metals ; Trinuclear copper complexes ; Dinuclear metal complex
• 刊名：Polyhedron
• 出版年：2013
• 出版时间：28 November, 2013
• 年：2013
• 卷：65
• 期：Complete
• 页码：200-205
• 全文大小：883 K

文摘

Macrocyclic N,N¡ä,N¡å,N¡å¡ä,N¡å¡å,N¡å¡å¡ä-hexakis(2-aminoethyl)-1,4,7,10,13,16-hexaazacyclooctadecane (haeh) and its complexes with Ni²⁺ and Cu²⁺ were synthesized. The protonation and formation constants with Ni²⁺, Cu²⁺, and Zn²⁺ were determined by pH-metry at 25 ¡ãC in a 0.5 mol dm^?3 KNO₃ aqueous solution. The macrocycle haeh forms stable di- and trinuclear species with Cu²⁺; log K(Cu₂(haeh)) = 38.84 ¡À 0.04 and log K(Cu₃(haeh)) = 49.08 ¡À 0.05. For Ni²⁺ and Zn²⁺, the macrocycle forms only a dinuclear complex; log K(Ni₂(haeh)) = 29.00 ¡À 0.02 and log K(Zn₂(haeh)) = 26.38 ¡À 0.02. These metal complexes show a significant tendency to form protonated and hydroxo species. The formation constants obtained are discussed on the basis of electrostatic repulsion and the flexibility of the macrocycles. The formation constants of the metal complexes were also determined at 15 and 35 ¡ãC in a 0.5 mol dm^?3 aqueous KNO₃ solution to obtain the thermodynamic parameters ¦¤H and ¦¤S. The results obtained showed that the stability of the copper complexes is dominated by ¦¤S.