Unusual Cross-Conjugation in Cyclic Dipeptide-Based Building Blocks for Donor-Acceptor Semiconducting Conjugated Polymers.

Cross conjugation, though prevalent in many organic compounds, is typically considered less effective for electron delocalization compared to linear conjugation. Consequently, it is rarely used as the backbone structure for semiconducting conjugated polymers. In this study, we designed and synthesized a novel building block, TIDP, which features a central cyclic dipeptide with cross conjugation characteristics. Strong intramolecular hydrogen bonding interactions confer TIDP with a highly rigid and coplanar conformation. Importantly, theoretical calculations reveal that π electrons are well delocalized across the entire structure, despite its low aromaticity. Conjugated polymers incorporating TIDP exhibit high charge carrier mobilities, demonstrating the effective π electrons delocalization of this innovative building block. Our findings show that with rational design, cross conjugation can achieve effective π electrons delocalization, providing a valuable approach for developing high-performance conjugated polymers for organic electronic materials.

Multivalent Phthalocyanine-Based Cationic Polymers with Enhanced Photodynamic Activity for the Bacterial Capture and Bacteria-Infected Wound Healing.

The solubility and photosensitive activity of phthalocyanine are crucial to photodynamic antibacterial performance. However, highly conjugated phthalocyanine with high singlet oxygen generation efficiency tends to aggregate in aqueous environments, leading to poor solubility and photodynamic antibacterial activity. Herein, we propose a novel photodynamic antibacterial therapeutic platform by a phthalocyanine-based polymeric photosensitizer for the efficient healing of a bacteria-infected wound. A prepared phthalocyanine-based chain-transfer agent and a tertiary amino group-containing monomer are applied in the reversible addition-fragmentation chain-transfer polymerization for the preparation of the polymeric photosensitizer, which is subsequently quaternized to obtain a positively charged surface. This water-soluble phthalocyanine-based polymer can strongly concentrate on bacterial membranes via electrostatic interaction. The formed singlet oxygen by the phthalocyanine-based polymer after 680 nm light irradiation plays an essential role in killing the Gram-positive and Gram-negative bacteria. The study of antibacterial action indicates that this nanocomposite can cause irreversible damage to the bacterial membranes, which can cause cytoplasm leakage and bacterial death. Moreover, this therapeutic platform has excellent biocompatibility and the capacity to heal the wounds of bacterial infections. Experimental results indicate that the design strategy of this phthalocyanine-based polymer can extend the application of the hydrophobic photosensitizer in the biomedical field.