Self-Assembled Pd₁₂ Coordination Cage as Photoregulated Oxidase-Like Nanozyme

Abstract

Designing supramolecular architectures with uncommon geometries embedded with functional building units is of immense importance in contemporary research. In this report, we present a new water-soluble Pd₁₂L₆ supramolecular coordination nanocage (<b>1</b>) that was synthesized via self-assembly of a tetradentate donor (<b>L</b>) with ditopic acceptor <i>cis</i>-[(en)Pd(NO₃)₂] [en = ethylenediamine]. Self-assembly of a tetratopic donor with a cis-blocked 90° acceptor commonly produces tri/tetra- or hexagonal barrel-type structures. However, the resulting cage <b>1</b> has an uncommon geometry consisting of two triangular cupolas conjoined through an irregular common hexagonal base. Incorporation of the benzothiadiazole unit in the structure helped in the photogeneration of reactive oxygen species (ROS) in water. Many nanomaterials have shown to have the ability to mimic the catalytic activity of natural enzymes (nanozymes). Majority of such nanozymes are water insoluble metal/metal-oxide nanoparticles or extended metal organic frameworks (MOFs)/metal-carbon composites, etc. The present water-soluble Pd₁₂ nanocage <b>1</b> has shown excellent oxidase-like activity upon irradiation with white light. The enzymatic activity of <b>1</b> is photoregulated which offers other obvious advantages, such as external control of enzymatic activity and noninvasiveness. The oxidase-like activity and exogenous ROS generation have been further exploited in photocatalytic antibacterial activity against methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) bacterial strain.