The Construction And Properties Of Red-Light Responsive Host-Guest System In Aqueous Phase

The development of water-soluble host-guest systems with long-wavelength light responsiveness is of great significance for the construction of drug delivery and controlled release systems,as well as bio-compatible dynamic functional materials.The research of this thesis mainly focuses on the construction of novel long wavelength(in particular,red-light within the biological window)responsive host-guest systems in water,and the systematically studies of their light-regulated guest encapsulation properties,which includes the following two parts:In the first part,two water-soluble photochromic guest molecules containing difluoro-substituted(1)or tetrachloro-substituted(2)azobenzene moieties have been synthesized,whose photo-regulated encapsulation behaviors with CB[8] macrocycles in aqueous solution were then investigated in detail by 1H NMR and UV/Vis spectroscopic techniques.The results showed that 1E and 2E can be encapsulated by CB[8] macrocycles to form 1:1 host-guest complexes of CB[8]· 1E and CB[8]·2E,respectively.Upon the irradiation with yellow light(? > 500 nm)(for CB[8]·1E)or red light(? = 650 nm)(for CB[8]·2E),the E?Z photoisomerization of the encapsulated 1E and 2E could be triggered,converting these complexes to CB[8]·1Z(Z/E > 92%)and CB[8]·2Z(Z/E > 93%)in a high isomerization ratio.Furthermore,the remaining host cavities of CB[8]·1E and CB[8]·2E could encapsulate a non-photoactive second guest(SG),respectively,leading to the generation of heteroternary host-guest complexes of CB[8]·1E·SG and CB[8]·2E·SG.The irradiation of yellow or red lights could trigger the E?Z photoisomerization of the encapsulated 1E and 2E in these heteroternary complexes,which resulted in the formation of CB[8]·1Z and CB[8]·2Z complexes accompanied by the release of the SG molecules owning to strong steric repulsion.We envision that such unique long wavelength(specially the red-light)activated photochromic host-guest systems will serve as promising tools in the fabrication of new bio-compatible drug delivery systems,as well as photoresponsive functional dynamic materials.In the second part,a novel water-soluble tetracationic macrocyclic host molecule incorporated with two tetra-chloro-azobenzene units has been synthesized,whose chemical structure was unquestionably confirmed by 1H NMR,13 C NMR and HR-MS characterizations.The preliminary results have showed that the tetra-chloro-azobenzene units in this macrocycle could undergo E?Z photo-isomerization under red light irradiation.Further studies of the photo-controlled host-guest complexation behaviors are currently underway.