Organic planar π-conjugated anions enable structural design of anion-π+ NIR-II phototheranostic agents

Abstract Anion-π + phototheranostic agents (PTAs) have attracted considerable interest for their exceptional luminescence and reactive oxygen species (ROS). However, current development is constrained by limited structural diversity and lack of second near-infrared (NIR-II) emission and photothermal performance, with the role of organic π-conjugated anions remaining unexplored. Here, we propose an organic π-conjugated anion-exchange strategy to construct advanced NIR-II PTAs. DTPAP-2B (with Br - ) and DTPAP-2P (with pentacyanocyclopentadiene anion ((CCN) 5 - )), were synthesized. Upon nanoformulation, DTPAP-2P NPs exhibit pronounced absorption redshift, intense NIR-II emission, a large Stokes shift (340 nm), superior ROS generation, and high photothermal conversion efficiency (72%) compared to DTPAP-2B NPs. Single-crystal and theoretical analyses reveal that the planar (CCN) 5 - anion enhances dual anion-π + interactions, promoting intramolecular charge transfer while suppressing intermolecular π-π stacking. This enables high-resolution NIR-II angiography and effective NIR-II imaging-guided synergistic photodynamic/photothermal therapy in female mice model. This work establishes organic π-conjugated anion exchange as a powerful strategy for developing robust NIR-II PTAs.