The photophysics of three benzothiazole derivatives that exhibit excited state intramolecular proton transfer (ESIPT) were investigated in a confined medium afforded by the water soluble supramolecular host octaacid (OA). The dye@(OA)₂ inclusion complexes were probed by UV-Vis absorption, steady-state and time resolved fluorescence emission techniques. Comparison studies of the free dyes in solution were also conducted. All three benzothiazole derivatives free in solution and as OA complexes in water absorb in the UV region. The fluorescence maxima of the OA complexes in water are similar to those in an apolar environment. This is different from the emission behavior of the dyes dissolved alone in water. The observed Stokes shift when confined within OA is related to the intramolecular proton transfer mechanism. Within OA only neutral species are present, indicating that these compounds are shielded from the bulk water. The excited state behavior of the benzothiazole derivatives in a confined medium indicates that supramolecular effects significantly alter the nature of the fluorescence emission.

Singlet oxygen (¹O₂) is the excited state electronic isomer and a reactive form of molecular oxygen, which is most efficiently produced through the photosensitized excitation of ambient triplet oxygen. Photochemical singlet oxygen generation (SOG) has received tremendous attention historically, both for its practical application as well as for the fundamental aspects of its reactivity. Applications of singlet oxygen in medicine, wastewater treatment, microbial disinfection, and synthetic chemistry are the direct results of active past research into this reaction. Such advancements were achieved through design factors focused predominantly on the photosensitizer (PS), whose photoactivity is relegated to self-regulated structure and energetics in ground and excited states. However, the relatively new supramolecular approach of dictating molecular structure through non-bonding interactions has allowed photochemists to render otherwise inactive or less effective PSs as efficient ¹O₂ generators. This concise and first of its kind review aims to compile progress in SOG research achieved through supramolecular photochemistry in an effort to serve as a reference for future research in this direction. The aim of this review is to highlight the value in the supramolecular photochemistry approach to tapping the unexploited technological potential within this historic reaction.

The excited state behavior of two flavone derivatives 3-hydroxyflavone and 4′-N,N-diethylaminoflavonol in a confined medium indicates that supramolecular effects could alter the nature of the fluorescence emission. Within the octa acid host the neutral unionized species of these two dyes are present showing large Stokes shifted emission due to intramolecular proton transfer, a pattern different from that in aqueous medium.