Visible Light and Microwave-Mediated Rapid Trapping and Release of Singlet Oxygen Using a Coordination Polymer

Abstract

Due to its high reactivity and oxidative strength, singlet oxygen (¹ O₂ ) is used in a variety of fields including organic synthesis, biomedicine, photodynamic therapy and materials science. Despite its importance, the controlled trapping and release of ¹ O₂ is extremely challenging. Herein, we describe a one-dimensional coordination polymer, CP1, which upon irradiation with visible light, transforms ³ O₂ (triplet oxygen) to ¹ O₂ . CP1 consists of Cd^II centers bridged by 9,10-bis((E)-2-(pyridin-4-yl)vinyl)anthracene ligands which undergo a [4+2] cycloaddition reaction with ¹ O₂ , resulting in the generation of CP1-¹ O₂ . Using microwave irradiation, CP1-¹ O₂ displays efficient release of ¹ O₂ , over a period of 30 s. In addition, CP1 exhibits enhanced fluorescence and has an oxygen detection limit of 97.4 ppm. Theoretical calculations reveal that the fluorescence behaviour is dominated by unique through-space conjugation. In addition to describing a highly efficient approach for the trapping and controlled release of ¹ O₂ , using coordination polymers, this work also provides encouragement for the development of efficient fluorescent oxygen sensors.

Keywords: Coordination Polymers; Fluorescent Sensing; Singlet Oxygen; Trap and Release; [4+2] Photocycloaddition Reaction.