title: Proton driven vase-to-kite conformational change in cavitands at an air-water interface monitored by surface SHG.
abstract: The conformational changes of quinoxaline-bridged cavitands deposited as Langmuir films were monitored at different pH values of the subphase using surface second harmonic generation during the compression of the monolayer at the water surface. A quantitative analysis of the susceptibility tensor elements was performed for methylene (MeCav)- and quinoxaline (QxCav)-bridged cavitands for pH values varying between 5.7 and 0.1. For MeCav (reference compound), no significant changes were observed for different pHs, confirming that the cavity does not undergo protonation or a drastic conformational change. For the QxCav, however, the results suggest a partial opening of the cavity on the basis of analysis of the compression curves.
authors.affiliation: Department of Physics, University of California Berkeley, 366 Leconte Hall, Berkeley, California 94720, USA.
authors.forename: François
authors.initials: F
authors.lastname: Lagugné-Labarthet
authors.forename: Yong Q
authors.initials: YQ
authors.lastname: An
authors.forename: Tao
authors.initials: T
authors.lastname: Yu
authors.forename: Yuen R
authors.initials: YR
authors.lastname: Shen
authors.forename: Enrico
authors.initials: E
authors.lastname: Dalcanale
authors.forename: Devanand K
authors.initials: DK
authors.lastname: Shenoy
mesh_terms: D000388:Air; D001672:Biocompatible Materials / Q000737:chemistry*; D004988:Ethers, Cyclic / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008422:Materials Testing; D008968:Molecular Conformation; D011312:Pressure; D011522:Protons; D011810:Quinoxalines / Q000737:chemistry; D012118:Resorcinols / Q000737:chemistry; D013499:Surface Properties; D013718:Tensile Strength; D014867:Water
chemical_list: D001672:Biocompatible Materials; D004988:Ethers, Cyclic; D011522:Protons; D011810:Quinoxalines; D012118:Resorcinols; C442939:cavitand; D014867:Water