Study Of Supramolecular Inclusion Complexes Of 2'-ethylhexyl-4-(N,N-dimethylamino)-benzoate And Cyclodextrin

Chapter 1:The recent advances in supramolecular inclusion complexes of cyclodextrins have been reviewed.The structure,property and the application of 2'-ethylhexyl 4-(N,N-dimethylamino)-benzoate(PAEHB)in sun-screening products and its molecular recognition and fluorescent sensing based on the TICT mechanism were briefly described.Chapter 2:The photophysical properties of PAEHB in various solvents at room temperature were characterized by the UV-Vis and fluorescence spectra.The results obtained indicate that the absorbance maximum shifts to the red with increasing solvent polarity. Dipole moment in excited state was larger than that in ground state,which is due to twisted intramolecular charge transfer.It was found that with increasing solvent polarity the dual fluorescence occurred and the TICT emission shifted to long wavelength at the same time. And the fluorescence intensity decreased.This finding would provide a theoretic gist based on intramolecular charge transfer for fluorescent sensing.Chapter 3:The mechanism of PAEHB complexed with natural and methylatedβ-CDs was investigated in water by fluorescence,~1H NMR measurements and anti-oxidation experiment.The results show that PAEHB form 2:1 cage-type host-guest inclusion complexes inβ-CD,DM-CD,HDM-CD and HTM-CD solution and all complexes exhibit dual fluorescence.On the one hand,the methyl substitution would increase the geometric resistance.On the other hand,the methyl substitution would decrease the polarity of CD cavity.Effect of number and position of methyl substituents on the geometric resistance was important.As a novel type of TICT fluorescent probe PAEHB would recognize the number and position of the methyl substituent.Chapter 4:The interaction between the PAEHB and unmodified and modifiedβ-CDs by hydroxypropyl was investigated in water by fluorescence and ~1H NMR measurements, n-hexyl alcohol competitive inclusion method and anti-oxidation experiment.The results indicate that PAEHB was stabilized within the 2:1 cage-type host-guest inclusion complexes. The inclusion complexes of PAEHB with unmodified and modifiedβ-CDs by hydroxypropyl exhibit dual fluorescence.The hydroxypropyl substituent would increase the polarity and the hydrophobicity of CD cavity.PAEHB as a novel type of TICT fluorescent probe would recognize the number of the hydroxypropyl group.Inclusion mechanism of PAEHB complexed with HP-CD was Van der Waals force,nonpolar interaction and hydrophobic interaction.Chapter 5:The interactions of PAEHB complexed withα-CD,β-CD andγ-CD were studied by means of fluorescence,n-hexyl alcohol competitive inclusion method and anti-oxidation experiment.It revealed that the 1:1α-CD:PAEHB inclision complex was formed at lower concentration ofα-CD and the addition ofα-CD resulted in the 2:1α-CD:PAEHB inclision complex.The formation of 2:1β-CD:PAEHB and 1:1γ-CD:PAEHB was examined.The 2:1α-CD:PAEHB and 2:1β-CD:PAEHB complexes exhibited dual fluorescence while no TICT fluorescence was observed in aqueousγ-CD solution.The cavity size effect on the TICT emission of PAEHB is very important.Chapter 6:The inclusion of PAEHB into methylatedβ-cyclodextrin(M-CD)and 2-hydroxypropyl-β-cyclodextrin(HP-CD)was examined by molecular spectra.PAEHB was stabilized within the 2:1 cage-type host-guest inclusion complexes.The hydrophobic 2-ethylhexyl tail greatly contributes to the extraordinarily stable complexes.The water solubility of PAEHB was increased by M-CD and HP-CD.The enhanced absorbance of PAEHB was obtained.The photodegradation of PAEHB was markedly reduced in aqueous solution.PAEHB was still stable in alkaline solutions of M-CD and HP-CD.Anti-oxidation and thermal stability were appreciably promoted at the same time.