Thiophene-based pyridine derivatives: synthesis, crystal structures, two-photon absorption properties and bio-imaging applications in the near-IR region

Abstract

Two novel D–π–A structural thiophene-based pyridine (N^N^N or N^N^C) chromophores have been designed and synthesized. Then they were characterized by ¹H NMR, ¹³C NMR, IR, MALDI-TOF-MS and single crystal X-ray diffraction analyses. Photophysical properties including UV-vis absorption, fluorescence, and two-photon absorption (2PA) spectra were systematically investigated using both theoretical and experimental methods. The results indicated that the thiophene-based chromophores displayed high fluorescence quantum yields and large active 2PA cross-sections in the near infrared region. Due to their excellent 2PA properties, low toxicity and low molecular weight, two-photon fluorescence microscopy (2PFM) images of HepG2 cells were captured, which suggested their potential applications in biological studies.