title: Substituent Effects in CH Hydrogen Bond Interactions: Linear Free Energy Relationships and Influence of Anions.
abstract: Aryl CH hydrogen bonds (HBs) are now commonly recognized as important factors in a number of fields, including molecular biology, stereoselective catalysis, and anion supramolecular chemistry. As the utility of CH HBs has grown, so to has the need to understand the structure-activity relationship for tuning both their strength and selectivity. Although there has been significant computational effort in this area, an experimental study of the substituent effects on CH HBs has not been previously undertaken. Herein we disclose a systematic study of a single CH HB by using traditional urea donors as directing groups in a supramolecular binding cavity. Experimentally determined association constants are examined by a combination of computational (electrostatic potential) and empirical (σm and σp) values for substituent effects. The dominance of electrostatic parameters, as observed in a computational DFT study, is consistent with current CH HB theory; however, a novel anion dependence of the substituent effects is revealed in solution.
authors.affiliation: Department of Chemistry & Biochemistry and the Materials Science Institute, University of Oregon , Eugene, Oregon 97403-1253, United States.
authors.forename: Blakely W
authors.initials: BW
authors.lastname: Tresca
authors.affiliation: Department of Chemistry & Biochemistry and the Materials Science Institute, University of Oregon , Eugene, Oregon 97403-1253, United States.
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: Hansen
authors.affiliation: Department of Chemistry & Biochemistry and the Materials Science Institute, University of Oregon , Eugene, Oregon 97403-1253, United States.
authors.forename: Calvin V
authors.initials: CV
authors.lastname: Chau
authors.affiliation: Supramolecular Design Institute , 127 Chestnut Hill Road, Oak Ridge, Tennessee 37830-7185, United States.
authors.forename: Benjamin P
authors.initials: BP
authors.lastname: Hay
authors.affiliation: CAMCOR, University of Oregon , 1443 East 13th Avenue, Eugene, Oregon 97403, United States.
authors.forename: Lev N
authors.initials: LN
authors.lastname: Zakharov
authors.affiliation: Department of Chemistry & Biochemistry and the Materials Science Institute, University of Oregon , Eugene, Oregon 97403-1253, United States.
authors.forename: Michael M
authors.initials: MM
authors.lastname: Haley
authors.affiliation: Department of Chemistry & Biochemistry and the Materials Science Institute, University of Oregon , Eugene, Oregon 97403-1253, United States.
authors.forename: Darren W
authors.initials: DW
authors.lastname: Johnson
mesh_terms: D000838:Anions; D002244:Carbon / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006859:Hydrogen / Q000737:chemistry*; D006860:Hydrogen Bonding; D066244:Proton Magnetic Resonance Spectroscopy
chemical_list: D000838:Anions; D002244:Carbon; D006859:Hydrogen