Switching Reactivity With Light: C─P Bonding Controls Singlet Oxygen Generation and Reactivity in Dimethyldihydropyrene-Cyclophanediene (DHP-CPD) Photoswitches.

The dimethyldihydropyrene photochromic system is a 14π-electronic framework that switches to a less-aromatic, nonplanar system under visible light. In this work, we unravel a neutral phosphorus heteroatom-appended dimethyldihydropyrene (DHP) photoswitchable system that acts as a self-sensitizer, enabling precise, wavelength-selective control over singlet oxygen capture with dual reactivity. The attachment of the phosphorus directly to the DHP scaffold allowed red light (640 nm) to selectively generate a phosphinate intermediate (DHP-2), while green light (525 nm) triggers further transformation into an endoperoxide. The dual reactivity can thus be selected easily by choosing the appropriate wavelength of light. The formation of the photoproducts also displayed dependence on the phosphine (DHP-1) concentration. Thus, this work establishes a unified approach to engineering singlet oxygen generation, wavelength-selective fixation, and release of singlet oxygen within a single molecular scaffold.