Beta-cyclodextrin And Its Derivatives Supramolecular Inclusion Complexes

A inclusion complex of 2,3,5,6-tetrachlorobenzoquinone(TCBQ) with -cyclodextrin (p-CD) has been synthesized and studied by FT-IR, powder X-ray diffractometry, UV-vis absorption spectroscopy and the electrochemical method. The results indicate that the ratio of P-CD to TCBQ in inclusion complex is 1:1 and TCBQ molecule was included in the hydrophobia cavity. When P-CD added to the TCBQ aqueous solution at 25 , the dissociated constant of the inclusion complex is 2.7 10-3mol-L-1. The inclusion complex can be reduced on glassy carbon electrode directly. The electrochemical cathodic peak potential 102mV (vs SCE) for the inclusion complex has a little shift in positive direction comparing to that for TCBQ. On the other hand, the diffusion coefficient of the inclusion complex is bigger than that of TCBQ. However, when synthesized inclusion complex dissolved in water, the dissociation occurred. At 25 ,the dissociation constant of inclusion complex is 3.8 10-7mol-L-1, which shows the inclusion complex is stable in water. The diffusion coefficient of inclusion complex is 8.03 10-5cm2-s-1 and its electrochemical cathodic peak potential is evaluated as 102mV (vs SCE).In this chapter, inclusion complex of TCBQ with hydroxypropyl- -cyclodextrin (HP-P-CD) were prepared based on the coprecipitation method. The interaction of TCBQ with HP-P-CD has been studied by several analytical techniques, including FT-IR, powder X-ray diffractometry, UV-vis absorption spectroscopy and the electrochemical method. The experimental results confirmed the existence of a 1:1 inclusion complex of TCBQ with HP- -CD. When HP- -CD added to the TCBQ aqueous solution at 25 , the dissociated constant of the inclusion complex is 6.9 10-4 mol-L-1. The inclusion complex can be reduced on glassy carbon electrode directly. The electrochemical cathodic peak potential for the inclusion complex has a little shift in positive direction comparing to that for TCBQ. Its cathodic peak potential is evaluatedas 108mV (vs SCE). The diffusion coefficient of the inclusion complex is 5.86 10-5cm2-s-1. However, when synthesized inclusion complex dissolved in water, the dissociation occurred. At 25 ,the dissociation constant of inclusion complex is 2.03 10-7mol-L-1, which shows the inclusion complex is stable in water. The diffusion coefficient of inclusion complex is 5.98 10-5cm2s-1 and its electrochemical cathodic peak potential is evaluated as 108mV (vs SCE).The stability constants of inclusion complexes of tetrachlorobenzoquinone, benzoquinone with cyclodextrins( -CD and HP- -CD) in aqueous solution were studied by UV-vis absorption spectroscopy at 10 , 15 , 20 , 25 and 30 , respectively. The influences of temperature on the inclusion actions were investigated. The apparent thermodynamic parameters were also obtained. The results demonstrated that van der Waals force( H <0, S<0, governed by AH ) is the major driving force of inclusion systems of tetrachlorobenzoquinone, benzoquinone with cyclodextrins(-CD and HP- -CD).