Extraordinary Control of Photosensitized Singlet Oxygen Generation by Acyclic Cucurbituril-like Containers

Abstract

Supramolecular control of singlet oxygen generation is incredibly valuable for several fields with broad applications and thus still challenging. However, macrocyclic inclusion complexes inherently restrict the interaction of photosensitizers with surrounding oxygen in the media. To circumvent this issue, we turned our attention in this work to acyclic cucurbituril-like containers and uncover their properties as supramolecular hosts for photosensitizers with extraordinary control of their photophysics, including singlet oxygen generation. Thermodynamic and photophysical studies were carried out showing that these acyclic containers compare very favorably to benchmark macrocycles such as cucurbiturils and cyclodextrins in terms of their binding affinities and supramolecular control of singlet oxygen generation. Acyclic container with terminal naphthalene walls offers a similar cavity to cucurbit[7]­uril and the same carbonyl-lined portals for a tight binding of phenothiazinium dye methylene blue and stabilizing its singlet and triplet excited states. Thus, generation of singlet oxygen for this container is higher than for other macrocycles and even higher than the free photosensitizer. While the acyclic container with smaller terminal benzene walls, stacks over the dye through sulfur−π and π–π interactions deactivating the singlet and triplet excited states, thus showing the lowest generation of singlet oxygen out of all of the studied systems. Due to the great water solubility and biocompatibility of these systems, they possess great potential for novel applications in photocatalysis, synthesis, and biomedical fields, among others.

Efficient Energy and Electron Transfer Photocatalysis with a Coulombic Dyad

“…For a meaningful comparison with the molecular dyad, PTS was used for the Coulombic dyad at the same concentration as Ruphen (60 µM), resulting in 92% including oxygen, do not yield any product formation. For comparison, traditional organic photocatalysts for singlet oxygen generation, such as rose bengal, methylene blue, and eosin Y, [118][119][120][121][122][123][124][125] were employed in the experiments. However, their performance was notably lower, with yields below 20% following irradiation under our standardized conditions (yellow, pink and pale blue traces in Figure 5 (b)), despite their considerably higher extinction coefficients in the green spectral region compared to the employed ruthenium complexes.…”