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Urea‐, Squaramide‐, and Sulfonamide‐Based Anion Receptors: A Thermodynamic Study
Author(s) -
Amendola Valeria,
Fabbrizzi Luigi,
Mosca Lorenzo,
Schmidtchen FranzPeter
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201003411
Subject(s) - chemistry , titration , sulfonamide , iodide , isothermal titration calorimetry , hydrogen bond , adduct , inorganic chemistry , binding constant , oxyanion , bromide , medicinal chemistry , stereochemistry , organic chemistry , molecule , binding site , biochemistry , catalysis
In this work, we compare the anion‐binding capabilities of receptors 1 – 5 , characterized by similar structures, but possessing different hydrogen‐bond‐donor moieties (urea, squaramide, and sulfonamide). The presence of chromophoric substituents on the receptor’s skeleton allowed the determination of association constants by performing UV/Vis titrations with the investigated anions on solutions of the receptors in pure acetonitrile. Additional quantitative studies of the anion‐binding properties of receptors 1 – 5 were performed by isothermal titration calorimetry (ITC). The experimental results indicated that 1 and 2 formed 1:1 hydrogen‐bonded complexes with most of the anions investigated. In the case of receptors 3 – 5 , the formation of the 1:1 adduct was observed only with anions of low basicity (i.e., chloride, bromide, iodide, and hydrogen sulfate). With more basic anions (i.e., acetate and dihydrogen phosphate), both spectrophotometric and ITC titrations accounted for the deprotonation of the sulfonamide group, involving the formation of the conjugated base of the receptor.