title: Control of hydrogen bond strengths through push-pull effects triggered by a remote reaction center: a theoretical study.
abstract: In an effort to manipulate the bond strengths of hydrogen bonds, we have studied a three-component chemical system consisting of a reaction center, a conjugated bridge, and a hydrogen-bonding site. Protonation of the reaction center triggers intramolecular charge transfer from the hydrogen-bonding site, altering its affinity to bind to an acceptor. Previously, we had found that this communication (signal transduction) between the reaction center and the hydrogen-bonding site does not necessarily die out with increasing length of the conjugated bridge. In certain cases, this signal transduction is maintained-and even amplified-over long distances (I. Chao, T.-S. Hwang, Angew. Chem. 2001, 113, 2775-2777; Angew. Chem. Int. Ed. 2001, 40, 2703-2705). In this study we report the results of an extensive theoretical investigation of this problem to provide insights into this intriguing phenomenon. In the systems we investigated it was found that the push-pull process between the hydrogen-bonding site and the protonatable reaction center was mediated with the greatest facility by conjugated bridges with low-lying pi and pi* orbitals.
authors.affiliation: Institute of Chemistry, Academia Sinica, Taipei 11529, Taiwan.
authors.forename: Tsong-Song
authors.initials: TS
authors.lastname: Hwang
authors.forename: Ning
authors.initials: N
authors.lastname: Juan
authors.forename: Hsing-Yin
authors.initials: HY
authors.lastname: Chen
authors.forename: Cheng-Chung
authors.initials: CC
authors.lastname: Chen
authors.forename: Shih-Jung
authors.initials: SJ
authors.lastname: Lo
authors.forename: Ito
authors.initials: I
authors.lastname: Chao
mesh_terms: D000641:Ammonia / Q000737:chemistry; D001665:Binding Sites; D006576:Heterocyclic Compounds, 4 or More Rings / Q000737:chemistry; D006860:Hydrogen Bonding; D008956:Models, Chemical; D008962:Models, Theoretical; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry; D011758:Pyrroles / Q000737:chemistry
chemical_list: D006576:Heterocyclic Compounds, 4 or More Rings; D009942:Organometallic Compounds; D011758:Pyrroles; D000641:Ammonia