Polyaza and azaoxa macrocyclic receptors functionalised with fluorescent subunits; Hg2+ selective signalling
作者:Youseff Al Shihadeh、Angel Benito、José Manuel Lloris、Ramón Martínez-Máñez、Teresa Pardo、Juan Soto、M. Dolores Marcos
DOI:10.1039/a908762a
日期:——
A polyazacycloalkane containing naphthyl groups, 1,4,8,11-tetrakis(naphthylmethyl)-1,4,8,11-tetraazacyclotetradecane (L1), and the azaoxa cycloalkane receptors containing anthracenyl groups, 7,13-bis(anthracenylmethyl)-1,4,10-trioxa-7,13-diazacyclopentadecane (L2) and 10-anthracenylmethyl-1,4,7-trioxa-10-azacyclododecane (L3), have been synthesized and their activity as fluorescent chemosensors studied towards the metal cations Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ in THF–water (70∶30 v/v, 0.1 mol dm−3 tetrabutylammonium perchlorate, 25 °C) for L1 and 1,4-dioxane–water (70∶30 v/v, 0.1 mol dm−3 potassium nitrate, 25 °C) for L2 and L3. The crystal structure of the complex [Cd(L1)(Cl)][PF6] has been determined by X-ray single crystal procedures. The co-ordination geometry about the cadmium atom is near square pyramidal with the ligand showing a conformation with the four naphthylmethyl groups pointing above the N4 plane. Potentiometric experiments in THF–water for L1 in the presence of Cu2+, Hg2+ and Pb2+ and in 1,4-dioxane–water for L2 in the presence of Cu2+, Zn2+, Cd2+, Hg2+, Pb2+, and L3 with Cd2+ and Pb2+ have also been carried out. All metals form stable complexes with L1, L2 and L3 with stability constants for the formation of the [M(L1)]2+, [M(L2)]2+ and [M(L3)]2+ species in the sequence Pb2+ < Hg2+ < Cu2+; Zn2+ < Cd2+ < Pb2+ < Cu2+ ≪ Hg2+ and Cd2+ < Pb2+, respectively. The fluorescent behaviour of L1, L2 and L3 in the presence of the Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ has been studied as a function of the pH: Cu2+ and Hg2+ selectively quench the fluorescence emission intensity of L1 at neutral and acid pH. The emission intensity of L2 is selectively enhanced in the presence of Hg2+ at basic pH. In contrast, the fluorescence intensity of the free receptor L3 at a certain pH is not modified upon addition of any metal ion. The emission sensing behaviour of L1, L2 and L3 towards metal ions is compared with the electrochemical sensing ability of analogous ferrocene-functionalised ligands.
含有
萘基的多氮杂环
烷烃,1,4,8,11-四(
萘基甲基)-
1,4,8,11-四氮杂环十四烷(L1),和含有
蒽基的氮杂恶环
烷烃受体,7,13-双(
蒽基甲基)- 1,4,10-三氧杂-7,13-二氮杂
环十五烷(
L2) 和 10-
蒽基甲基-1,4,7-三氧杂-10-
氮杂环十二烷 (L3) 已合成,并研究了它们作为荧光
化学传感器对 THF-
水中
金属阳离子 Cu2+、Zn2+、Cd2+、Hg2+ 和 Pb2+ 的活性(70∶30 v/v,0.1 mol dm−3
高氯酸四丁基
铵, L1 为 25 °C,
L2 和 L3 为 1,4-
二恶烷-
水(70∶30 v/v,0.1 mol dm−3
硝酸钾,25 °C)。络合物[Cd(L1)(Cl)][PF6]的晶体结构已通过X射线单晶程序确定。
镉原子的配位几何形状接近方锥体,
配体显示出四个
萘甲基指向N4平面上方的构象。在存在 Cu2+、Hg2+ 和 Pb2+ 的情况下,在 THF-
水中进行了 L1 的电位实验;在存在 Cu2+、Zn2+、Cd2+、Hg2+、Pb2+ 和 L3 的情况下,在 1,4-二氧杂
环己烷-
水中进行了
L2 的电位实验,并与 Cd2+ 和 Pb2+ 进行了电位实验。已进行。所有
金属均与 L1、
L2 和 L3 形成稳定的络合物,其稳定常数可形成 Pb2+ 序列中的 [M(L1)]2+、[M(
L2)]2+ 和 [M(L3)]2+ 物质< Hg2+ < Cu2+;分别为 Zn2+ < Cd2+ < Pb2+ < Cu2+ ≪ Hg2+ 和 Cd2+ < Pb2+。研究了存在 Cu2+、Zn2+、Cd2+、Hg2+ 和 Pb2+ 时 L1、L2 和 L3 的荧光行为与 pH 的函数关系:Cu2+ 和 Hg2+ 在中性和酸性 pH 下选择性猝灭 L1 的荧光发射强度。在碱性 pH 值下,当 Hg2+ 存在时,L2 的发射强度会选择性增强。相反,游离受体L3在一定pH下的荧光强度不会因添加任何金属离子而改变。将 L1、L2 和 L3 对金属离子的发射传感行为与类似的二茂铁官能化配体的电
化学传感能力进行了比较。