Fluorous effects in amide-based receptors for anions.
Hybrid receptors designed to recognize both the sulfonate headgroup and the fluorous tail of perfluorooctanesulfonate (CF(3)(CF(2))(7)SO(3)(-), "PFOS") were prepared by coupling fluorinated carboxylic acids onto poly(aminomethyl)benzene scaffolds. Binding to PFOS, CF(3)SO(3)(-), p-TsO(-), and Cl(-) was monitored by (1)H NMR and isothermal titration calorimetry (ITC). In chloroform solvent, hydrogen-bonding to anions is accompanied by downfield shifts in the amide NH protons of the fluorinated receptors and by evolution of heat. Association constants for 1:1 complexation (K(assoc)) are >1000 M(-1). An analogous hydrocarbon receptor binds weakly to anionic guests (K(assoc) < 50 M(-1)). Ab initio calculations indicate that the differences in 1:1 binding strengths between fluorous and nonfluorous hosts cannot be ascribed to differences in NH donor acidities.
Gavette
Jesse V
JV
Department of Chemistry, Science and Technology Building, East Carolina University, Greenville, North Carolina 27858-4353, USA.
McGrath
Jacqueline M
JM
Spuches
Anne M
AM
Sargent
Andrew L
AL
Allen
William E
WE
D017738:Alkanesulfonic Acids / Q000737:chemistry; D000577:Amides / Q000737:chemistry*; D005466:Fluorocarbons / Q000737:chemistry*; D007525:Isoelectric Focusing; D013379:Substrate Specificity; D013816:Thermodynamics
D017738:Alkanesulfonic Acids; D000577:Amides; D005466:Fluorocarbons; C076994:perfluorooctane sulfonic acid