Study of the Calix[4]resorcinarene-Dopamine Interactions in Monolayers by Measurement of Pressure-Area Isotherms and Maxwell Displacement Currents
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- 作者：Martin Weis ; Radoslav Janí ;
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- 刊名：Journal of Physical Chemistry B
- 出版年：2007
- 出版时间：September 6, 2007
- 年：2007
- 卷：111
- 期：35
- 页码：10626 - 10631
- 全文大小：130K
- 年卷期：v.111,no.35(September 6, 2007)
- ISSN：1520-5207
文摘
The mechanisms of interactions between calix[4]resorcinarene and dopamine in monolayers formed at theair-water interface were studied by analyzing their mechanical, thermodynamic, and electrical propertiesevaluated from measurements of pressure-area isotherms and Maxwell displacement currents (MDCs). Anincreased concentration of dopamine in the water subphase resulted in an increase in the area per calix[4]resorcinarene molecule, an increase in the collapse pressure, and a shift in the monolayer phase transitionsfrom the gaseous to the liquid state and from the liquid to the solid state toward higher molecular areas. Acontactless method of recording MDCs enabled the monitoring of changes in the charge state of the monolayer-constituting molecules and the determination of a relationship between the phase state of the monolayer andthe structural transitions of calix[4]resorcinarene. The changes of the MDC recordings started already in thegaseous state of the monolayer. On the basis of MDC values, we determined the normal component of thedipole moment of calix[4]resorcinarene, as well as that of its complex with dopamine. The dipole momentreached a maximum value of 1040 mD in the region of the phase transition from the liquid to the solid stateof the monolayer. The results obtained suggest that the binding of dopamine with calix[4]resorcinarene dependson the orientation of the calixarene molecules in the monolayer. The calix[4]resorcinarene-dopamineinteractions were also quantified in terms of the excess of Gibbs free energy, thereby allowing the evaluationof the energy of the calix [4]resorcinarene-dopamine bond, which was in the range from 1.95 to 8.54 kJ/moldepending on the surface pressure. This value implies weak interactions between these molecules.