Preventing the Photodegradation of Anthracene-Based Photosensitizers through the Formation of Zn(II) Molecular Tweezers.

Abstract

We report the preparation and photophysical investigations of molecular tweezers incorporating photosensitizing anthracene units and a central terpyridine moiety. In its W-shaped open form, the ligand L1 (R = -C≡CPh) can both generate and trap singlet oxygen upon blue light illumination, ultimately leading to photodegradation. A different behavior is observed upon zinc coordination in the presence of 2,2':6',2″-terpyridine, where the formed heteroleptic complex adopts a U-shaped closed form. This geometry renders the complex more resistant toward oxidation by singlet oxygen than the parent ligand L1. Furthermore, the heteroleptic complex efficiently produces singlet oxygen under blue light illumination with the best photostability and singlet oxygen quantum yield obtained in 1,2-dichloroethane. The ability of the complex to generate singlet oxygen was successfully applied in a photooxygenation reaction.