Synthesis, crystal structures, one/two-photon optical properties and bioimaging application of two organic molecules with D-A and D-π-A models containing 6-phenyl-2,2′-bipyridine

Two novel organic compounds with D-A (L1) and D-pi-A (L2) models containing 4-(N,N-dipropylamino)phenyl [donor group (D)] and 6-phenyl-2,2-bipyridine [acceptor (A)] groups were synthesized and characterized by IR, H-1 NMR, C-13 NMR, MS and single crystal X-ray diffraction. Their photophysical properties were systematically investigated using both experiments and theoretic calculations. It was found that the two-photon action cross-section (phi) of the D-pi-A model molecule (phi(L2) = 119 GM) was approximately three times larger than that of the D-A type molecule (phi(L1) = 43 GM). Furthermore, their cytotoxicity and applications in bioimaging were determined. The results showed that L1 and L2 could be used as cytoplasmic dyes with high stability and low cytotoxicity.