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A microcalorimetric study on molecular recognition of p-sulfonatocalix[4]arene derivatives at selfassembled interface in comparison with in bulk water was performed,inspired by the dramatic change in physicochemical characteristics from bulk water to interface.A total of six cationic molecules were screened as model guests,including ammonium(NH_4~+),guanidinium(Gdm~+).N,N’-dimethyl-1,4-diazabicyclo[2.2.2]octane(DMDABCO~(2+)),tropylium(Tpm~+),N-methyl pyridinium(N-mPY*) and methyl viologen(MV~(2+)).The complexation with NH_4~+.Gdm~+ and DMDABCO2* is pronouncedly enhanced when the recognition process moved from bulk water to interface,whereas the complexation stabilities with Tpm~+,N-mPY~+ and MV2* increase slightly or even decrease to some extent.A more interesting phenomenon arises from the NH_4~+/Gdm~+ pair that the thermodynamic origin at interface differs definitely from each other although with similar association constants.The results were discussed in terms of differential driving forces,electrostatic,hydrogen bond as well as π-stacking interactions,originating from the unique physicochemical features of interfaces,mainly the polarity and dielectric constant.
A microcalorimetric study on molecular recognition of p-sulfonatocalix [4] arene derivatives at comparison with bulk water was performed, inspired by the dramatic change in physicochemical characteristics from bulk water to interface. A total of six cationic molecules were screened as model guests, including ammonium (NH 4 ~ +) and guanidinium (Gdm ~ +). N, N’-dimethyl-1,4- diazabicyclo [2.2.2] octane (DMDABCO ~ ), N-methyl pyridinium (N-mPY *) and methyl viologen (MV ~ (2 +)). The complexation with NH_4 ~ + .Gdm ~ + and DMDABCO2 * is pronouncedly enhanced when the recognition process moved from bulk water to interface , while the complexation stabilities with Tpm ~ +, N-mPY ~ + and MV2 * increase slightly or even decrease to some extent. A more interesting phenomenon arises from the NH_4 ~ + / Gdm ~ + pair that the thermodynamic origin at a different concept from each other although with similar association constants. The results were discussed in terms of differential drivin g forces, electrostatic, hydrogen bond as well as π-stacking interactions, originating from the unique physicochemical features of interfaces, mainly the polarity and dielectric constant.