Emerging Near‐Infrared Optical Materials Based on Supramolecular Charge Transfer Complexes

ABSTRACT

Organic charge transfer complexes (CTCs), formed by donor–acceptor (D–A) coassembly, have emerged as a supramolecular platform for programmable near‐infrared (NIR) optics. In their D–A assemblies, packing‐dependent electronic coupling and delocalization generate tunable charge transfer (CT) states and typically yield redshifted absorption and emission relative to the constituent molecules. This review establishes a structure‐function framework that links D–A energetics, noncovalent interactions, and packing geometry to emergent NIR optical states. Recent progress is summarized across practical material forms, including cocrystals, nanoparticles, confined assemblies, thin films, and soft matrices. We outline design principles that relate molecular selection and supramolecular organization to (i) broadband and NIR absorption, (ii) NIR emission, and (iii) polarization activity and reconfigurable optics across different material forms. In this context, low‐energy CT states formed upon photoexcitation often favor nonradiative relaxation and photothermal conversion. Efficient NIR emission, by contrast, requires preserving radiative CT pathways while suppressing nonradiative loss in low‐energy assembled states. Polarization‐active and reconfigurable responses further arise from chiral or oriented D–A organization and stimulus‐responsive CT structural changes. Overall, this review provides structure‐function guidelines for the rational engineering of organic CTCs toward programmable NIR functional optics and adaptive infrared photonic systems.