Complexation of 1,4-Bis(pyridinium)butanes by Negatively Charged Carboxylatopillar[5]arene
作者:Chunju Li、Xiaoyan Shu、Jian Li、Songhui Chen、Kang Han、Min Xu、Bingjie Hu、Yihua Yu、Xueshun Jia
DOI:10.1021/jo201185e
日期:2011.10.21
and binding modes. 3- and 4-Substituted guests (12+, 32+, 42+, 62+, 72+) form [2]pseudorotaxane geometries with CP5A host, giving very large association constants (>105 M–1), while 2,6-dimethyl-substituted 52+ forms external complex with relatively small Ka values [(2.4 ± 0.3) × 103 M–1] because the 2,6-dimethylpyridinium unit is too bulky to thread the host cavity. Both of the binding geometries mentioned
取代的1,4-双(吡啶)丁烷衍生物(X-Py(CH 2)4 Py-X,X = H,2-甲基,3-甲基,4-甲基,2,6-二甲基,通过1 H NMR和2D ROESY以及在磷酸盐缓冲水溶液中的UV吸收和荧光光谱,对4-带吡啶基和4-COOEthyl)1 2+ – 7 2+带负电荷的羧基吡咯烷酮[5]芳烃(CP5A)进行了全面研究。(pH 7.2)。结果表明,吡啶环上连接的取代基的位置显着影响缔合常数和结合方式。3位和4位代客(1 2 +,3 2 +,4 2+,6 2 +,7 2+)与CP5A主体形成[2]伪轮烷形状,给出非常大的缔合常数(> 10 5 M –1),而2,6-二甲基取代的5 2+形成外部复合物,其缔合常数相对较小K a的值为[(2.4±0.3)×10 3 M –1 ],因为2,6-二甲基吡啶单元体积太大,无法穿通主体腔。对于吡啶2的2-位具有一个甲基的2 2+,观察到上述两种结合几何形状。通常,[2]假轮烷1