Stimuli Responsive Confinement of a Molecular Rotor Based BODIPY Dye inside a Cucurbit[7]uril Nanocavity

Present study reports the interaction of a molecular rotor based BODIPY dye, 8-anilino-BODIPY (ABP), with a versatile macrocyclic molecule, cucurbit[7]uril (CB7), investigated through various techniques such as ground-state absorption, steady-state fluorescence, time-resolve emission, proton NMR, and quantum chemical studies. Although BODIPY dyes have widespread applications due to their intriguing photochemical properties, studies on their noncovalent interactions with different macrocyclic hosts, especially regarding their supramolecularly induced modulations in photophysical properties are very limited. The investigated BODIPY dye, especially its protonated ABPH(+)form (pH similar to 1), shows a large fluorescence enhancement on its interaction with the CB7 host, due to large reduction in the structural flexibility for the bound dye, causing a suppression in its nonradiative de-excitation process in the excited state. Unlike ABPH(+), the neutral ABP form (pH similar to 7) shows considerably weaker interaction with CB7. For ABPH(+)-CB7 system, observed photophysical results indicate formation of both 1:1 and 1:2 dye-to-host complexes. Plausible geometries of these complexes are obtained from quantum chemical studies which are substantiated nicely from H-1 NMR results. The response of the ABPH(+)-CB7 system toward changing temperature of the solution have also been investigated elaborately to understand the potential of the system in different stimuli-responsive sensor applications.

Automated summary

The study investigates the interaction between a molecular rotor-based BODIPY dye and a versatile macrocyclic molecule CB7 using various techniques, revealing a significant fluorescence enhancement, reduced structural flexibility, and formation of 1:1 and 1:2 dye-to-host complexes. The potential of the system in different stimuli-responsive sensor applications is also explored by examining its response to changing temperature.