Synthesis, Biomacromolecular Interactions, Photodynamic NO Releasing and Cellular Imaging of Two [RuCl(qn)(Lbpy)(NO)]X Complexes

Two light-activated NO donors [RuCl(qn)(Lbpy)(NO)]X with 8-hydroxyquinoline (qn) and 2,2′-bipyridine derivatives (Lbpy) as co-ligands were synthesized (Lbpy(1) = 4,4′-dicarboxyl-2,2′-dipyridine, X = Cl(−) and Lbpy(2) = 4,4′-dimethoxycarbonyl-2,2′-dipyridine, X = NO(3)(−)), and characterized using ultraviolet–visible (UV-vis) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance ((1)H NMR), elemental analysis and electrospray ionization mass spectrometry (ESI-MS) spectra. The [RuCl(qn)(Lbpy(2))(NO)]NO(3) complex was crystallized and exhibited distorted octahedral geometry, in which the Ru–N(O) bond length was 1.752(6) Å and the Ru–N–O angle was 177.6(6)°. Time-resolved FT-IR and electron paramagnetic resonance (EPR) spectra were used to confirm the photoactivated NO release of the complexes. The binding constant (K(b)) of two complexes with human serum albumin (HSA) and DNA were quantitatively evaluated using fluorescence spectroscopy, Ru-Lbpy(1) (K(b)~10(6) with HSA and ~10(4) with DNA) had higher affinity than Ru-Lbpy(2). The interactions between the complexes and HSA were investigated using matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS) and EPR spectra. HSA can be used as a carrier to facilitate the release of NO from the complexes upon photoirradiation. The confocal imaging of photo-induced NO release in living cells was successfully observed with a fluorescent NO probe. Moreover, the photocleavage of pBR322 DNA for the complexes and the effect of different Lbpy substituted groups in the complexes on their reactivity were analyzed.