Arshad Khan

The ability to precisely control fluorescence variations holds significant promise for applications in advanced display technologies, bioimaging, and optical sensors. However, achieving solid-state emission enhancement within a single system remains a challenge. In this study, we have developed two-component charge transfer (CT) aggregates composed of carbazole-derived donor (9-phenyl-9H-carbazole (PC) and 9-(p-tolyl)-9H-carbazole (TC)) and acceptor (2,3,5,6-tetrafluoroterephthalonitrile (TFN)) molecules exhibiting distinct enhancement in solid-state emission properties. Structural analysis reveals that the PC–TFN (4 : 1) cocrystal adopts a DAD⋯DAD configuration, while the TC–TFN (1 : 1) cocrystal forms a DADA arrangement, indicating strong CT interactions. The cocrystals exhibit a pronounced redshift in both UV absorption and fluorescence emission along with enhanced fluorescence quantum yields of 74.70% for PC–TFN and 54.07% for TC–TFN, and extended lifetime attributed to the CT interactions facilitated by π⋯π stacking between donor and acceptor molecules. Furthermore, quantum chemical calculations offer detailed insights into the modulation of luminescence properties, providing a more profound understanding of CT interactions and presenting a new strategy for designing materials with tunable fluorescence behavior.

The field of molecular charge transfer cocrystals (CTCs) has advanced rapidly in recent years, with much work focused on their use in optoelectronic devices, photoacoustic imaging, photothermal therapy (PTT), optical waveguides, seawater desalination, and more. Organic photothermal CTCs are of particular interest because of their unique phototherapeutic effects in phototherapy and their remarkable imaging capabilities in fluorescence, magnetic resonance, and photoacoustic imaging, further enhancing their significance in medical applications. However, the use of photothermal CTCs in biomedicine has been limited, with few reported biological applications. Hence, there is a growing interest in CT‐derived functional photothermal cocrystals potential contenders for targeted and controlled biomedical applications such as bacteria inhibition, cancer eradication, and tissue regeneration. This review offers insight into the recent advancements in crafting and producing CT‐based materials with biomedical attributes. In addition, it outlines the current obstacles and future prospects in this burgeoning research domain, aiming to propel the continued advancement of CT‐based biomaterials toward enhanced biomedical utilities. Overall, cocrystal‐based near‐infrared (NIR) photothermal materials have the potential to revolutionize a wide range of medical and technological applications and are an active area of research in chemistry, materials science, and nanotechnology.

C₂₅H₂₉BN₂O₂, monoclinic, P2₁/c (no. 14), a = 13.1591(3) Å, b = 13.9362(3) Å, c = 13.0463(3) Å, β = 112.066(3)°, V = 2217.29(10) ų, Z = 4, R _gt (F) = 0.0419, wR _ref (F ²) = 0.1068, T = 150 K.

C₂₆H₂₇BN₄, monoclinic, C2/c (no. 15), a = 38.716(3) Å, b = 9.2723(6) Å, c = 27.3977(18) Å, β = 113.4790(10)°, V = 9021.1(11) ų, Z = 16, R_gt(F) = 0.0520, wR_ref(F²) = 0.1440, T = 100 K.