Visible light-harvesting tricarbonyl Re(I) complex: synthesis and application in intracellular photodynamic effect and luminescence imaging

Abstract

Re(I) tricarbonyl rhenium(I) complexes attracted much attention owing to the good cellular uptake ability and rich photophysical properties. However, normally Re(I) complexes show short triplet state lifetime and weak absorption in the visible spectra region, and the absorption wavelength usually is shorter than 450 nm. These features are detrimental to the applications of Re(I) complexes in the areas such as photodynamic therapy (PDT) and luminescence bioimaging. Herein, a novel tricarbonyl rhenium(I) complex Re-1 with strong visible light-absorbing ability (624 nm, e=5.69×104 L/(mol cm)), long-lived triplet excited state (τ T=448.9 μs) and moderate fluorescence quantum yield (Φ F=41.6%) was prepared. The photophysical properties of Re-1 were studied with steady state UV-Vis absorption and luminescence spectroscopies, nanosecond transient absorption spectroscopy, as well as DFT/TDDFT calculations. Re-1 was used for intracellular PDT and luminescence imaging studies. The results indicate that Re-1 shows low dark toxicity, but it is able to kill cancer cells on illumination with 635 nm LED.