Synthesis and spectroscopic properties of symmetrically substituted two-photon absorbing molecules with rigid elongated π-conjugation

Facile synthesis of a two-photon fluorescent probe based on pyrimidine 2-isothiocyanate and its application in bioimaging

Two-photon microscopy imaging has been widely applied in biological imaging, but the development of two-photon absorption probes is obviously lagging behind in the development of imaging technology. In this paper, a two-photon fluorescent probe (1) based on pyrimidine 2-isothiocyanate has been designed and synthesized through a simple method for two-photon biological imaging. Probe 1 was able to couple effectively with the amino groups on biomolecules. To verify the reactivity of the isothiocyanate group on probe 1 and the amine groups on the biomolecules, d-glucosamine was chosen as a model biomolecule to conjugate with probe 1. The result showed that probe 1 could effectively conjugate with d-glucosamine to synthesize probe 2, and the yield of probe 2 was 83%. After conjugating with d-glucosamine, linear absorption spectra, single-photon fluorescence spectra, and two-photon fluorescence spectra of probes 1 and 2 did not present significant changes. Probes 1 and 2 exhibited high fluorescence quantum yields (0.71-0.79) in toluene and chloroform. They also exhibited different photo-physical properties in solvents with different polarities. The two-photon absorption cross-section of probe 1 was 953 GM in toluene. In addition, probe 1 could be effectively conjugated with transferrin, and the conjugated probe (Tf-1) could be transported into Hep G2 cells through a receptor-mediated process for biological imaging. These results demonstrate that such probes are expected to have great potential applications in two-photon fluorescence bioimaging.

Experimental and theoretical studies of the spectroscopic properties of simple symmetrically substituted diphenylacetylene derivatives

A series of symmetrically substituted diphenylacetylene derivatives possessing electron-donating or electron-accepting character were prepared and studied with respect to their spectral and photophysical properties.

Acetylene-Substituted Two-Photon Absorbing Molecules With Rigid Elongated Pi-Conjugation: Synthesis, Spectroscopic Properties and Two-Photon Fluorescence Cell Imaging Applications

Two asymmetrical molecules with substituted acetylene as central rigid elongated conjugation are reported as potential chromophores for two-photon microscopic imaging. These molecules consist of a typical D-pi-A structure, have different donors (D), the same pi-conjugated center (pi) and the same acceptor (A). Structural characterization and spectroscopic properties, including single-photon (linear) absorption, quantum yields, single-photon fluorescence, and two-photon absorption spectra, were studied in solvents with different polarity. These acetylene-substituted molecules were found to have high two-photon absorption cross-sections (for example, 690 GM for molecule 1 in toluene), which were determined by a two-photon induced fluorescence method using a femtosecond Ti: sapphire laser as excitation source. Single- and two-photon cellular imaging experiments demonstrate that the substituted acetylene derivatives could be one kind of promising two-photon fluorescence probes for cellular imaging.