Inversion of selectivity in anion recognition with conformationally blocked calix[4]pyrroles
作者:Raúl Gotor、Ana M. Costero、Salvador Gil、Margarita Parra、Luis E. Ochando、Katherine Chulvi
DOI:10.1039/c2ob26309b
日期:——
Two calixpyrrole derivatives were synthesised. A p-dimethylaminobenzoyl group was electronically attached to a pyrrole ring, establishing an intramolecular hydrogen bond in a 1,3-alternate conformation. The formation of the H-bond was corroborated by IR, NMR, and X-ray measurements. NMR titration studies reveal that the H-bond is strong enough to block the conversion to a cone conformation, allowing them to only acquire a partial cone conformation. Affinity constants for several anions were calculated, and a noticeable increase was observed for tridentate tetrahedral anions, while the Ka of spheric or bidentate anions decreased. In the presence of several acids, the synthesised compounds can act as chemosensors by a double process: protonation of the amino group and coordination of the generated anion. In addition, a displacement approach gives rise to a proof of concept for sulphonate recognition.
合成了两种杯吡咯衍生物。对二甲氨基苯甲酰基以电子方式连接到吡咯环上,以 1,3-交替构象建立分子内氢键。通过红外、核磁共振和 X 射线测量证实了氢键的形成。核磁共振滴定研究表明,氢键足够强,足以阻止向锥体构象的转化,从而使它们只能获得部分锥体构象。计算了几种阴离子的亲和常数,并且观察到三齿四面体阴离子的Ka显着增加,而球形或二齿阴离子的Ka下降。在几种酸存在的情况下,合成的化合物可以通过双重过程充当化学传感器:氨基的质子化和生成的阴离子的配位。此外,置换方法还提供了磺酸盐识别的概念验证。