Bis-amidocarbazolyl urea receptor for short-chain dicarboxylate anions

Urea receptor 1 based on two (1-amino-8-amido-3,6-dichloro)carbazole units shows a strong association with dicarboxylate anions such as oxalate, malonate and succinate guests through multiple hydrogen bonds from the carbazole, urea and amide NH groups. (1)H NMR complexation studies exhibit high values of association constants in DMSO-d(6). X-ray structures of the 1?:?1 complexes of 1 with oxalate and malonate as their ditetrabutylammonium salts were obtained. A modelling study of the complex of receptor 1 with succinate (as its diTBA salt) showed a more reduced geometric complementarity than its homologue malonate.