Rationally designed two-photon absorption compounds based on benzoxazole derivatives: structure–property relationships and bio-imaging applications

Abstract

A new series of benzoxazole-based two-photon absorption (2PA) chromophores (T1–5) were synthesized and fully characterized. Among them, T1–3 are linear donor (D)–π–acceptor (A) type fluorophores with various electron-donating groups, while T4 and T5 are multi-branched compounds stemming from T3. Their photophysical properties have been systematically investigated, and the two-photon absorption properties indicate that the highest 2PA cross-section (σ_2PA) is 2702 GM for T5 (in DMF). Structure–property relationships of the chromophores are comprehensively discussed based on their optical properties, crystal structures and density functional theory (DFT) calculations. In addition, a two-photon fluorescence cell imaging experiment demonstrates the potential bio-application of T1–5 with good photostability and low cytotoxicity.