title: Tuning and dissecting electronic and steric effects in ammonium receptors: nonactin vs artificial receptors.
abstract: Ion selective electrodes (ISE) based on three different tripodal receptors (5, 6, and 7) have been investigated for sensing ammonium ion. Each receptor is based on three pyrazole groups that can accept three H-bonds from the bound ammonium ion. The receptor based on 4-bromo-3,5-dimethylpyrazole (6) is the most sensitive with a detection limit for ammonium ion of 2.5 x 10(-5) M at pH 8. The detection limits for the receptors based on 2,3-dimethylpyrazole (5) and unsubstitued pyrazole (7) are 1.0 x 10(-4) and 2.0 x 10(-4) M, respectively. The selectivities of the receptors 5, 6, and 7 for sensing ammonium ion over potassium ion (logK(NH)4+(/K)+) are -2.8, -2.3, and -1.7, respectively. In contrast, the detection limit and the selectivity of a nonactin-based ISE are 2.2 x 10(-5) M and -1.3, respectively. Crystallographic studies reveal that 6 accepts three H-bonds from the bound ammonium and singly protonated receptor 5 forms three H-bonds with the bound water molecule.
authors: Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada. jchin@chem.utoronto.ca
authors: Jik
authors: J
authors: Chin
authors: Jinho
authors: J
authors: Oh
authors: Sang Yong
authors: SY
authors: Jon
authors: Sang Hyun
authors: SH
authors: Park
authors: Christian
authors: C
authors: Walsdorff
authors: Brent
authors: B
authors: Stranix
authors: Assaad
authors: A
authors: Ghoussoub
authors: Seok Jong
authors: SJ
authors: Lee
authors: Hyun Jei
authors: HJ
authors: Chung
authors: Su-Moon
authors: SM
authors: Park
authors: Kimoon
authors: K
authors: Kim
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004566:Electrodes; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D018942:Macrolides / Q000737:chemistry*; D015394:Molecular Structure; D011720:Pyrazoles / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D011955:Receptors, Drug / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000900:Anti-Bacterial Agents; D018942:Macrolides; D011720:Pyrazoles; D000644:Quaternary Ammonium Compounds; D011955:Receptors, Drug; C050476:nonactin