Advancements in organic fluorescent materials: unveiling the potential of peripheral group modification in dithienyl-diketopyrrolopyrrole derivatives for one- and two-photon bioimaging†

The quest for novel organic fluorescent materials capable of two-photon absorption (2PA) has intensified in recent years due to their promising applications in biological imaging. Two-photon fluorescence microscopy (2PFM) offers high spatial-temporal resolution, reduced photodamage, and deeper tissue penetration compared to conventional techniques. However, the development of bright two-photon molecular markers remains a challenge, necessitating compounds with high fluorescence quantum yield and 2PA cross-section (σ^2PA). Strategies such as increasing π-conjugation have shown promise but are hindered by synthesis complexities and limited biocompatibility. Alternatively, incorporating electron-donating (ED) or electron-withdrawing (EW) peripheral groups in a main structure has emerged as a viable approach, leading to significant enhancements in σ^2PA. This study highlights the advantages and challenges of these strategies, emphasizing the importance of exploring new organic compounds and evaluating the efficacy of peripheral groups for advanced two-photon bioimaging applications.