RESUMEN
A bis-branched [3]rotaxane, with two [2]rotaxane arms separated by an oligo(para-phenylenevinylene) (OPV) fluorophore, was designed and investigated. Each [2]rotaxane arm employed a difluoroboradiaza-s-indacene (BODIPY) dye-functionalized dibenzo[24]crown-8 macrocycle interlocked onto a dibenzylammonium in the rod part. The chemical structure of the [3]rotaxane was confirmed and characterized by (1)H and (13)C NMR spectroscopy and high-resolution ESI mass spectrometry. The photophysical properties of [3]rotaxane and its reference systems were investigated through UV/Vis absorption, fluorescence, and time-resolved fluorescence spectroscopy. An efficient energy-transfer process in [3]rotaxane occurred from the OPV donor to the BODIPY acceptor because of the large overlap between the absorption spectrum of the BODIPY moiety and the emission spectrum of the OPV fluorophore; this shows the important potential of this system for designing functional molecular systems.
Asunto(s)
Transferencia de Energía , Colorantes Fluorescentes/química , Polivinilos/química , Rotaxanos/química , Estructura Molecular , Espectrometría de FluorescenciaRESUMEN
A prototype, based on light-active fluorescent rotor grafted to beta-cyclodextrin, shows a good solvent viscosity-sensitive behavior due to the environment-dependent nonradiative decay. With the reversible photoisomerization of the cyanostilbene unit, the viscosity sensitivity of the molecular rotor could be locked and activated, and the two switchable states can be distinguished by fluorescent signals. This cyclodextrin derivative was threaded to form a novel polypseudorotaxane. Such supramolecular assembly displays a lockable ratiometric fluorescent viscosity sensitivity with two emission channels: one aroused by fluorophore's intramolecular excimer without influenced by viscosity is used to gauge the concentration of the compound, while the other corresponding to the monomer's rotor fluorescence acts as a viscosity-sensitive signal and it can be shut off by UV irradiation.