Design,Synthesis And Properties Of Novel Photochromic[2]Rotaxanes With Dual Spectral Variation

This dissertation is focused on the design and synthesis of two novel photochromic[2]rotaxanes,and their dual spectral variation properties upon UV/Visible light irradiation are systematically investigated.It mainly includes the following two parts:In the first section,a threading-followed-by-stoppering approach is employed to synthesize the target photochromic[2]rotaxanes of R1 and R2,whose structures consist of a dumbbell component interlocked with a tetracationic CBPQT4+ as macrocyclic component.Their axles are incorporated with photochromic azobezene(AB)moity and electrorich 1,5-naphthalenediol(DNP)(for Rl)or difluorobenzidine(DFBZ)(for R2)units as two recognition sites,respectively.Both R1 and R2 have been fully characterized by 1H NMR,13C NMR and high-resolution mass spectroscopies.In the second part,the photochromic behaviors of Rl and R2 in acetonitrile are detailly studied with 1H NMR and UV-Vis spectroscopic experiments.It is revealed that the shuttling of CBPQT4+ ring on the dumbbell can be trigged by the E/Z photoisomerization of AB units upon the UV/Visible light irradiation.The ring is preferred to sit on the AB recognition site in the E-isomer photostationary state(PSSE),whereas in PSSz it tends to complex the DNP or DFBZ units.This makes R1 and R2 exhibit dual spectral change properties:one is caused by the E/Z photoisomerism of the AB moieties;and the other is due to the enhancement of the charge-transfer(CT)absorption bands corresponding to the DNP(?)CBPQT4+ or DFBZ(?)CBPQT4+ complexes after UV light irradiation.Since the CT bands are out of the photochromically active absorption region of R1 or R2,non-destructive readout of optical information could be achieved by employing the CT bond region as output signal.