Syntheses And Bioimaging Applications Of Novel Ruthenium Complex-based Phosphorescence Probes

Different from singlet state emitters,such as conventional fluorescent molecules,luminescent Ru(?)complexes are triplet emitters with long emission lifetimes.Ruthenium(?)complexes are considered to be the most extensively useful transition metal complexes as molecular reporters owing to their desirable features including the intense visible absorption and emission;large Stokes shift;long luminescence lifetime;high photo,thermal,and chemical stabilities;and very low cytotoxicity.In this doctoral dissertation,several ruthenium(?)complex-based phosphorescence probes for small bioactive molecules were designed and synthesized.After the phosphorescence properties of the probes were systematically investigated,the probes were successfully used for the luminescent imaging detection of biological samples.A unique ruthenium(?)complex,[Ru(bpy)2(DNS-bpy)](PF6),that can act as a probe for the recognition and luminescence sensing of biothiols was designed and synthesized.Due to the presence of effective photo-induced electron transfer(PET)from the potent electron donor(Ru-bpy centre)to the strong electron acceptor(2,4-dinitrophenyl moiety),the Ru(?)complex itself is weakly luminescent.Reaction of[Ru(bpy)2(DNS-bpy)](PF6)with biothiols leads to the replacement of the 2,4-dinitrophenyl moiety by biothiols,which results in the loss of PET within the complex,to allow recovery of the MLCT-based emission of the Ru(?)complex with an 80-fold increase in luminescence intensity.After the luminescence properties of[Ru(bpy)2(DNS-bpy)](PF6)were characterized,it was successfully used for the luminescence imaging of biothiols in living cells and Daphnia magna.Three heterobimetallic ruthenium(?)-nickel(?)complexes,Ru1-Ni,Ru2-Ni and Ru3-Ni,were designed and synthesized as phosphorescence probes for the detection of histidine.Because the phosphorescence of the Ru(?)complex can be strongly quenched by the paramagnetic Ni2+ ion,the probes exhibited weak emission.While Ni2+ has high binding affinity to histidine,in the presence of histidine,Ni2+ could be released from the complex Rul-Ni,which results in a remarkable phosphorescence enhancement of the Ru(?)complex.The detection limit for histidine is 265 nM.After the luminescence properties of Rul-Ni were well characterized,this probe was successfully used for the luminescence imaging of biothiols in living cells,zebrafish and Daphnia magna.Using the method that a lysosomal targeting group and a biothiol recognition group were introduced into the ligands of a ruthenium(?)complex,a novel ruthenium(?)complex,Ru-?,was designed and synthesized as a probe for the phosphorescence and time-gated luminescence detection of biothiols.Ru-? showed high selectivity and sensitivity for the detection of biothiols under physiological conditions,with detection limits of 62 nM,146 nM,and 115 nM for GSH,Cys,and Hcy,respectively.The introduction of a lysosomal targeting group(morpholine moiety)ensures Ru-? molecules to be driven into lysosomes of live cells after the incubation,to enable lysosomal biothiols to be imaged.After the possibility of time-gated luminescence detection of biothiols using Ru-? as a probe was confirmed,the probe was successfully used for the quantification of biothiols in human serum samples,as well as the luminescence imaging of biothiols in living cells and Daphnia magna.The results of this probe provide a useful strategy for the design and time-gated luminescence bioassay application of organelle targetable phosphorescence probes of Ru(?)complexes.