Self-Assembly and Photochemistry of a Pyrene-Methyl Viologen Supramolecular Fiber System

Abstract

This paper reports the self-assembly of a donor−acceptor system into nanoscopic structures and the photo processes taking place within these structures. The donor employed is pyrene linked to two β-cyclodextrin molecules (CD-PY-CD), and adamantane-linked methyl viologen attached to the three arms of mesitylene (Ms-(MV 2+ -AD) 3 ) is the acceptor. CD-PY-CD and Ms-(MV 2+ -AD) 3 when dissolved in water self-assembled into vesicles, which joined together to give long fibers. The self-assembly was studied using spectroscopic and microscopic techniques. Fluorescence of the pyrene chromophore was quenched within the selfassembled system due to efficient photoinduced electron transfer to methyl viologen. Photoinduced electron transfer within the assembly is confirmed through identification of product radical ions in flash photolysis experiments. Steady-state irradiation of the self-assembled system in an optical bench led to the formation of methyl viologen radical cation, which was stable for a few hours. Longevity of the radical cation was attributed to the fast reaction of pyrene radical cation with adjacent pyrene to give an unstable adduct, which slows down the back electron transfer process.

Fluorescence Quenching by Redox Molecular Pumping

“…The same behavior was also observed (Table S1 and Figure S46) in Me 2 CO. This quenching of the fluorescence can be attributed to a photoinduced electron transfer between the PYR unit in the dumbbell and the CBPQT 4+ rings on account of their closeness to each other . In order to confirm that the pumping event results in the quenching of the fluorescence of the PYR unit, control experiments were performed.…”

Confining charge-transfer complex in a metal-organic framework for photocatalytic CO2 reduction in water

“…Furthermore, the D–A interaction can be exploited for channeling the electron flow based on the push-pull effect to the catalytic center to carry out catalytic reactions. Additionally, the charge transfer complex would also result in a low energy absorption band to harvest visible light to generate photo-modulated electron-hole pair with low exciton binding energy 9 , 11 . Recently, MOFs have been extensively studied as a photocatalyst for CO 2 RR due to their promising CO 2 capture ability, high surface area, and textural properties 12 – 18 .…”