Theoretical Study On Structure And Properties Of Photoswitchable Cage And Cyclic Macromolecules

Photoswitches have been widely used in important fields such as supramolecular self-assembly,information storage,and ion receptors.Due to the unique switching structures of common photoswitches such as azobenzene,acylhydrazone,spiropyran,and diarylethene,they have been favored by academics.Cage or macrocycles are common molecular or ion receptors,which have a wide range of applications in ion recognition and ion trapping.By embedding photoswitches into cages or macrocycles,light-triggered isomerization is expected to alter the affinity of receptor molecules for ions,enabling controllable ion capture and release.However,studies in this area are rarely reported,mainly due to the difficulty of synthesis of macrocycles or cages embedded in photoswitchable,the high cost of direct preparation and experimental research,and the strong blindness.Therefore,the photochemical properties of macrocycles or cage photoswitches and their affinity for ions were first investigated using computational methods,it has important theoretical guiding significance for the development of controllable ion receptors.In this thesis,four cage photoswitches are designed,azobenzene cage,acylhydrazone cage,spiropyran cage and diarylethene cage.Investigated their photochemical properties and potential applications in ion recognition using density functional theory.In addition,four macrocycles containing azobenzenes or acylhydrazones were designed and their ability to adsorb sodium chloride ion pairs was discussed.The main research contents of this thesis are as follows:(1)Design of photoswitchable cages.The cage containing three 4,4’-dimethylamine azobenzene branches reported in the literature is used as the parent molecule in this thesis from a theoretical standpoint.By using different types of photoswitches and modifying the groups at the branched link,four different photoswitches embedded cages were obtained,azobenzene,acylhydrazone,spiropyran and diarylethene.The physicochemical properties of these four cages were studied.First,the differences in the cavity structure of the E/Z isomers of the cages were compared.The results show that from E to Z isomers of azobenzene cage,the overall cage height is reduced by nearly half,and the central cross section is also increased.The acylhydrazone cage changes from E to Z isomers,and the volume in the cavity is greatly reduced.From E to Z isomers of spiropyran cage,there is bond cleavage and new bond generation on the branched chain,and the overall length increases slightly.A ring-closure reaction occurs on the branched chain from E to Z isomers of diarylethene cage.With the formation of new bonds,the atoms on each branched chain are close to coplanar,and the overall length does not change significantly.Second,the UV-vis absorption spectra of E/Z isomers were simulated.The results show that,the azobenzene cage E isomer can be measured at 496.45 nm in the blue-green visible region with an n-π*absorption peak,the absorption peak has an obvious red shift,and the Z isomer can detect the π-π*absorption peak at 319.87 nm in the ultraviolet region.The absorption peak of diarylethene cage E isomer was measured at 357.67 nm,the absorption peak of the Z isomer was measured at 625 nm in the orange visible region,and the absorption peak had a significant red shift.(2)The ability of azobenzene cage to recognize cations.Through molecular topology analysis and absorption spectrum fitting,the recognition properties of azobenzene cage for nine metal cations were investigated inthis thesis.It was found that the Cu2+ ions were non-covalently bound to the azobenzene cage,and caused a red shift of about 89 nm in the absorption wavelength of cage,However,the other tested cations(including Cu+)did not interact with the azobenzene cage,and there is no obvious change in the absorption spectrum of the cage combined with ions.Therefore,the azobenzene cage calculated in this thesis may be used as a specific recognition receptor for Cu2+ ions,which is worthy of further experimental research.(3)Design of photoswitches sodium chloride ion-pair receptors.In this thesis,four kinds of macrocycles were designed with the Cl’ ion or NaCl ion pair receptor reported in the literature as the parent molecule,the photoswitches and the flexible crown ether chain were introduced.The binding ability of these four macrocycles to NaCl ion pairs was investigated.The results show that,there is a macrocycle embedded with an acylhydrazone photoswitchable,and the E/Z isomers have obvious differences in the affinity of the NaCl ion pair,which deserves further research.Based on this,it is expected to develop the photoswitches NaCl ion-pair extractant.