Liquid−Liquid Extraction of Alkali Metal Ions with Photochromic Crowned Spirobenzopyrans
作者:Hidefumi Sakamoto、Takashi Yokohata、Tsuyoshi Yamamura、Keiichi Kimura
DOI:10.1021/ac020003p
日期:2002.6.1
On the liquid−liquid extraction using 1,2-dichloroethane as an organic solvent, the crowned spirobenzopyrans exhibited textractability in the following order: Li+ ≫ Na+ > K+ ≥ tetramethylammonium ion (TMA+), Li+ > Na+ ≫ K+ > TMA+, and Na+ > K+ ≫ Li+ > TMA+ for spirobenzopyran derivatives bearing monoaza-12-crown-4, 1; monoaza-15-crown-5, 2; and monoaza-18-crown-6, 3; respectively, under dark conditions. The ion selectivity of 1 depends on the metal-ion complexing ability of monoaza-12-crown-4. Even 2, which carries a 15-crown-5 moiety, showed Li+ selectivity because of the much stronger interaction of Li+ with the phenolate ion of the merocyanine form of 2 than that of Na+. The Na+ selectivity of 3 is also attributed to the ionic interaction with the phenolate ion of the merocyanine form, since the ionic interaction prefers Na+ to K+ regardless of the higher affinity of the 18-crown-6 ring itself to the latter ion. The Li+ extraction into the organic phase with 1 was enhanced by UV irradiation (300−400 nm), while some depression in the extraction was found by visible irradiation (>500 nm). The effect of visible irradiation on the Li+ complexing ability of 1 was also examined with electrospray ionization mass spectrometry.
以 1,2-二氯乙烷为有机溶剂进行液-液萃取时,冠螺苯并吡喃按以下顺序表现出质地可萃取性:在黑暗条件下,单氮杂-12-冠-4(1)、单氮杂-15-冠-5(2)和单氮杂-18-冠-6(3)的螺苯并吡喃衍生物分别表现出 Li+ ≫ Na+ ≫ K+ ≥ 四甲基铵离子(TMA+)、Li+ ≫ Na+ ≫ K+ ≫ TMA+,以及 Na+ ≫ K+ ≫ Li+ ≫ TMA+。1 的离子选择性取决于单aza-12-冠-4 的金属离子络合能力。即使是含有 15-冠醚-5 分子的 2,也显示出 Li+ 的选择性,这是因为 Li+ 与 2 的经花青素形式的苯酚离子的相互作用要比 Na+ 强得多。3 的 Na+ 选择性也归因于与美拉德花青形式的苯酚离子之间的离子相互作用,因为离子相互作用更倾向于 Na+ 而不是 K+,尽管 18-crown-6 环本身对 K+离子的亲和力更高。紫外线照射(300-400 纳米)增强了 1 对有机相中 Li+ 的萃取,而可见光照射(>500 纳米)则抑制了萃取。此外,还利用电喷雾电离质谱法研究了可见光辐照对 1 的 Li+ 络合能力的影响。