双臂型方酰胺多齿配体的合成

Synthesis of Novel Multidentate Ligands with Two Arms Derived from Squaric Acid

自1959年发现方酸以来,已有许多文献报道其可以与多种金属离子,尤其是过渡金属离子形成配合物,但方酰胺多齿配体的研究却不多。在方酰胺内鎓盐中,二氧环丁烯具有电荷分离特性,其上的氧原子带部分负电荷,是理想的配体原子。如果以它为中心,对称地引入具有配位能力的分子片段。

Eight new multidentate ligands(5a～5f,5i,5j)have been synthesized by refluxing squaric acid with amines 4 which were obtained from chlorides 2 or alcohols 1 through nitro-compounds 3(3f,3g and 4f have not been hitherto reported).These chromo-genic ligands showing maximum absorption around 410 nm with lgε≈4.4 contain a dioxocyclo-butene skeleton and two arms of oligoethylene glycol ethers which allow the negatively charg-ed oxygen atoms on the four-membered ring to serve as central coordinating atoms.Veryinterestingly,5c turned out to be a good active constituent for NH_3-selective electrode,inaddition to its coordinations to UO_2^(2+) and ZrO^(2+).This phenomenon is supposed to originatefrom the interaction between the small and highly positively charged squaric ring and ligandNH_3 bearing a pair of unshared electrons.