Proton Driven Vase-to-Kite Conformational Change in Cavitands at an Air−Water Interface Monitored by Surface SHG

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 el...

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Bibliographic Details
Published in:Langmuir 2005-08, Vol.21 (16), p.7066-7070
Main Authors: Lagugné-Labarthet, François, An, Yong Q, Yu, Tao, Shen, Yuen R, Dalcanale, Enrico, Shenoy, Devanand K
Format: Article
Language:English
Subjects:
Air
Biocompatible Materials - chemistry
Chemistry
Ethers, Cyclic - chemistry
Exact sciences and technology
Gas-liquid interface and liquid-liquid interface
General and physical chemistry
Hydrogen-Ion Concentration
Materials Testing
Molecular Conformation
Pressure
Protons
Quinoxalines - chemistry
Resorcinols - chemistry
Surface physical chemistry
Surface Properties
Tensile Strength
Water
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Summary: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.
ISSN:0743-7463
1520-5827
DOI:10.1021/la050821n