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–π–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, 1H NMR, 13C 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 (δΦ) of the D–π–A model molecule (δΦL2 = 119 GM) was approximately three times larger than that of the D–A type molecule (δΦL1 = 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.