The synthesis of calix[4](aza)crowns capped by one ‘tren’ or doubly capped by two azacrowns is described. The crystal structure of the tripodal ‘tren’ is given. Complexing properties towards Co2+, Ni2+, Zn2+ and Cu2+ are described. Conclusions are drawn on the role of functional groups and molecular topology in the complexation behavior of calix[4](aza)crowns.
Calix[4]azacrowns as Novel Molecular Scaffolds for the Generation of Visible and Near-Infrared Lanthanide Luminescence
作者:Issam Oueslati、Rute A. Sá Ferreira、Luís D. Carlos、Carlos Baleizão、Mário N. Berberan-Santos、Baltazar de Castro、Jacques Vicens、Uwe Pischel
DOI:10.1021/ic051159l
日期:2006.3.1
bridges, were used as ligands for the complexation of lanthanide ions [Eu(III), Tb(III), Nd(III), Er(III), La(III)]. The formation of 1:2 and 1:1 complexes was observed, and stability constants, determined by UV absorption and fluorescence spectroscopy, were found to be generally on the order of log beta(11) approximately 5-6 and log beta(12) approximately 10. The structural changes of the ligands upon La(III)
两个杯盖[4] azazrowns,两个氨基聚酰胺桥封顶,用作配体镧系元素离子[Eu(III),Tb(III),Nd(III),Er(III),La(III)]的络合。观察到了1:2和1:1配合物的形成,并且通过紫外线吸收和荧光光谱确定的稳定性常数通常约为log beta(11)约5-6和log beta(12)通过1 H NMR光谱探测到La(III)络合后配体的结构变化。观察到两个配体具有相反的荧光行为,即金属离子络合时荧光增强(通过阻止胺基的光致电子转移)或猝灭(通过镧系元素与发色团相互作用)。长寿命镧系元素的发光被pi中的激发所敏化,配体的芳族部分的π带。通过Tb(III)淬灭配体磷光证明了天线三重态的直接参与。通常,Eu(III)发光较弱(Phi(lum)