Self-Assembled Pt^II₈ Metallosupramolecular Tubular Cage as Dual Warhead Antibacterial Agent in Water

Abstract

Development of photosensitizer-based self-assembled metallosupramolecular architectures with important applications is an emerging trend in supramolecular chemistry. In this study, we report a new benzothiadiazole-based tetra-pyridyl ligand (<b>L</b>), which upon self-assembly with a <i>cis-</i>block 90° Pt(II) acceptor generated an unprecedented tetrafacial Pt(II)₈ photoactive tubular molecular cage (<b>PMB1</b>). This cage could bring an extraordinary photosensitizer, benzothiadiazole, into water which is otherwise insoluble. <b>PMB1</b> is fluorescent and shows photogeneration of singlet oxygen in an aqueous medium. These features make <b>PMB1</b> a potent antimicrobial agent in water in both the presence and absence of light. In comparison to its building blocks and water-soluble alkylated charged ligand (<b>[L</b>_<b>Me4</b><b>][4NO</b>_<b>3</b><b>]</b>), the cage shows much enhanced photoinduced antibacterial activity against methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) as a representative of Gram-positive bacteria and <i>Pseudomonas aeruginosa</i> (PA) as a representative of Gram-negative bacteria. <b>PMB1</b> is successful at inactivating the bacterial growth via both photoactivation of molecular oxygen and membrane depolarization mechanisms, thus proving to be a dual warhead. Inactivation of bacteria in water using such a supramolecular architecture is noteworthy and can shed light on the generation of new antimicrobial supramolecular systems.