Efficient Photoinduced Energy and Electron Transfers in a Tetraphenylethene-Based Octacationic Cage Through Host-Guest Complexation.

Artificial photofunctional systems with energy and electron transfer functions, inspired from photosynthesis in nature, have been developed for many promising applications including solar cell, biolabeling, photoelectric materials, and photodriven catalysis. Supramolecular hosts including macrocycles and cages have been explored for simulating photosynthesis based on a host-guest strategy. Herein, we report a host-guest approach by using a tetraphenylethene-based octacationic cage and fluorescent dyes to construct artificial photofunctional systems with energy and electron transfer functions. The cage traps various dyes within its hydrophobic cavity to form 1:1 host-guest complexes via CH-π, π-π, and/or electrostatic interactions in solution. The efficient energy transfer and ultrafast photoinduced electron transfer between the cage and dyes are competitive processes with each other in artificial photofunctional systems. Spectroscopic techniques that confirm energy transfer from the fluorescent cage to dyes (e.g., NiR, R700, and R800) are efficient, which induce the red shift of fluorescence. On the other hand, ultrafast photoinduced electron transfer from dyes (e.g., ICG, AG, and AV) to the fluorescent cage can induce fluorescence quenching. This study provides an insight into the construction of artificial photofunctional systems with energy and electron transfer functions via a host-guest approach in solution.