Potentiometric and spectrophotometric studies of the equilibria between silver(I) ion and crown ethers containing chromophore substituents in propylene carbonate
作者:Tadeusz Ossowski、Jaromir Kira、Dorota Rogowska、Hanna Warmke、Janusz Młodzianowski
DOI:10.1039/a908585h
日期:——
Potentiometric and UV-spectrophotometric methods have been used to study the coordination properties of crown ethers and their derivatives containing 9,10-dioxo-1-anthryl, 8-hydroxy-9,10-dioxo-1-anthryl and 8-tosyloxy-9,10-dioxo-1-anthryl substituents with respect to the silver(I) ion in propylene carbonate. It was found that unsubstituted crown ligands were capable of forming two types of complex ion. The silver(I) ion can enter the macrocycle cavity forming 1∶1 complexes or can coordinate externally to the nitrogen atom of a ligand as occurs for typical complexes of silver(I) with nitrogen ligands. This results in Ag(crown)2+ complexes. Introduction of chromophore groups allows investigation of the mechanism of AgL+ and AgL2+ complex formation by spectrophotometric methods. Attaching a bulky chromophore to the nitrogen atom of the aza-crown makes the formation of the AgL2+ complexes for monoaza-crown-15 strongly restricted or impossible. For 13-(9,10-dioxo-1-anthryl)-1,4,7,10-tetraoxa-13-azacyclopentadecane (A215C5AQN) the presence of only one substituent leads to an increase in the stability of the external complex (AgL2) and the formation of other complex structures Ag2L32+ and Ag3L23+.
采用电位计法和紫外分光光度法研究了含有 9,10-二氧代-1-蒽基、8-羟基-9,10-二氧代-1-蒽基和 8-三羟基-9,10-二氧代-1-蒽基取代基的冠醚及其衍生物与碳酸丙烯酯中银(I)离子的配位特性。研究发现,未取代的冠配体能够形成两种类型的络离子。银(I)离子可以进入大环空腔形成 1∶1 复合物,也可以从外部与配体的氮原子配位,如银(I)与氮配体的典型复合物。这就形成了 Ag(crown)2+ 复合物。引入发色团可以通过分光光度法研究 AgL+ 和 AgL2+ 复合物的形成机理。在氮杂皇冠的氮原子上连接一个大的发色团,会使单氮杂皇冠-15 的 AgL2+ 复合物的形成受到很大限制,甚至不可能形成。对于 13-(9,10-二氧代-1-蒽基)-1,4,7,10-四氧杂-13-氮杂环十五烷(A215C5AQN),只有一个取代基的存在会导致外部络合物(AgL2)的稳定性增加,并形成其他络合物结构 Ag2L32+ 和 Ag3L23+。