Two functional [2]rotaxanes featuring efficient intercomponent interactions between chromophores

• Two functional [2]rotaxanes with two fluorophores were synthesized by “click” reaction in a moderate yield.
• Efficient energy transfer between two fluorophores happened in two [2]rotaxanes.
• The emission intensity of [2]rotaxane 1 had a significant increase upon addition of excess DBU because of less efficient PET process.

Two functional [2]rotaxanes, with a 4-morpholin-naphthalimide fluorophore as one of the two stoppers and a difluoroboradiaza-s-indacene functionalized dibenzo[24]crown-8 as macrocycle, were designed, synthesized and well characterized. [2]Rotaxane 1 and 2 had almost the same structural skeleton, and a ferrocene unit was introduced in [2]rotaxane 1 as the other stopper, while a 3,5-dimethoxybenzene stopper in [2]rotaxane 2. It has shown that efficient energy transfer process in both two [2]rotaxanes occurred from the 4-morpholin-naphthalimide donor to the difluoroboradiaza-s-indacene acceptor. Moreover, [2]rotaxane 1 exhibited a remarkable fluorescence increase in response to the addition of base that can drive the shuttling motion because of the introduction of ferrocene electron donor. This work can pave the way for the design and construction of complex and functional molecular systems based on the mechanically interlocked molecules.

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