Construction Of Orthogonal Photoresponsive Tristable [3]Rotaxane With Nondestructive Readout

The unique multiple-states controllability enables multi-stable rotaxanes to be potentially applicable in the construction of more sophisticated molecular systems with advanced functions.It is of fundamental important to choose appropriate orthogonal stimuli for the construction of multi-stable rotaxanes,among which the distinct class of orthogonal photoresponsive multi-stable rotaxanes are extremely attractive for the clean and spatiotemporal resolution of using different light sources as external stimuli.However,owing to the lack of applicable orthogonal photoswitchable photochromophores that can be used as recognition sites,so far,it still remains a grand challenge to construct a multi-stable rotaxane featuring with unique orthogonal photoresponsiveness.In this thesis,a novel orthogonal photoresponsive tristable[3]rotaxane（R1）is rationally designed and synthesized,which contains two CBPQT⁴⁺macrocycles interlocked by a thread with three recognition sites including photoswitchable naphthalene-derived azobenzene（NP-AB）and azobenzene（AB）units separated by a 1,5-dioxynaphthalene（DNP）unit.The two CBPQT⁴⁺macrocycles are found to prefer to encapsulated with two azo units in the pristine state of R1.While upon UV（365 nm）/yellow（>550 nm）lights irradiation can trigger the reversible Z/E photoisomerization of AB unit and drive the CBPQT⁴⁺macrocycle shuttling between AB and DNP units,the irradiation with blue（420-430 nm）/yellow（>550 nm）lights can trigger the Z/E photoisomerization of NP-AB unit and drive the CBPQT⁴⁺macrocycle shuttling between NP-AB and DNP units.Furthermore,the charge transfer（CT）absorption band of R1 was able to exhibit reversible spectral changes during the orthogonal light irradiation cycles,resulting from the content variation of the NP（?）CBPQT⁴⁺encapsulation complexes of R1 driven by the alternating phototriggered Z/E photoisomerization of the NP-AB and AB units.In addition,the UV light-irradiated AB-contained[2]rotaxane or the blue light irradiated NP-AB embedded[2]rotaxane analogues are found to be insensitive to the red light（620nm）irradiation,based on which the obtained R1 is expected to be endowed with novel non-destructive readout feature when its CT absorption variation at 620nm is applied as the output signals.