title: Synthesis and anion binding studies of tris(3-aminopropyl)amine-based tripodal urea and thiourea receptors: Proton transfer-induced selectivity for hydrogen sulfate over sulfate.
abstract: Tris(3-aminopropyl)amine-based tripodal urea and thiourea receptors, tris([(4-cyanophenyl)amino]propyl)urea (L1) and tris([(4-cyanophenyl)amino]propyl)thiourea (L2), have been synthesized and their anion binding properties have been investigated for halides and oxoanions. As investigated by1H NMR titrations, each receptor binds an anion with a 1:1 stoichiometryviahydrogen-bonding interactions (NH⋯anion), showing the binding trend in the order of F-> H2PO4-> HCO3-> HSO4-> CH3COO-> SO42-> Cl-> Br-> I in DMSO-d6. The interactions of the receptors were further studied by 2D NOESY, showing the loss of NOESY contacts of two NH resonances for the complexes of F-, H2PO4-, HCO3-, HSO4-or CH3COO-due to the strong NH⋯anion interactions. The observed higher binding affinity for HSO4-than SO42-is attributed to the proton transfer from HSO4-to the central nitrogen ofL1orL2which was also supported by the DFT calculations, leading to the secondary acid-base interactions. The thiourea receptorL2has a general trend to show a higher affinity for an anion as compared to the urea receptorL1for the corresponding anion in DMSO-d6. In addition, the compoundL2has been exploited for its extraction properties for fluoride in water using a liquid-liquid extraction technique, and the results indicate that the receptor effectively extracts fluoride from water showing ca. 99% efficiency (based onL2).
authors.affiliation: Department of Chemistry and Biochemistry, Jackson State University, Jackson, MS 39217, USA.
authors.forename: Maryam Emami
authors.initials: ME
authors.lastname: Khansari
authors.affiliation: Department of Chemistry and Biochemistry, Jackson State University, Jackson, MS 39217, USA.
authors.forename: Corey R
authors.initials: CR
authors.lastname: Johnson
authors.affiliation: Department of Chemistry and Biochemistry, Jackson State University, Jackson, MS 39217, USA; Department of Chemistry, Balikesir University, 10145, Balikesir, Turkey.
authors.forename: Ismet
authors.initials: I
authors.lastname: Basaran
authors.affiliation: Department of Chemistry and Biochemistry, Jackson State University, Jackson, MS 39217, USA.
authors.forename: Aemal
authors.initials: A
authors.lastname: Nafis
authors.affiliation: Department of Chemistry and Biochemistry, Jackson State University, Jackson, MS 39217, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Chemistry and Biochemistry, Jackson State University, Jackson, MS 39217, USA.
authors.forename: Jerzy
authors.initials: J
authors.lastname: Leszczynski
authors.affiliation: Department of Chemistry and Biochemistry, Jackson State University, Jackson, MS 39217, USA.
authors.forename: Md Alamgir
authors.initials: MA
authors.lastname: Hossain