Development Of Fluorescent Probes Based On Spirocyclic Rhodamines And Their Applications In Fluorescence Imaging

Fluorescence analysis have received great attention owing to their simplicity of implementation,good selectivity and high sensitivity.In recent years,fluorescent probes have developed rapidly based on specific recognition.It has been widely used to detect biologically reactive small molecules,especially for monitoring their production and elucidating biological roles.Rhodamine B is one of the most commonly as molecular probes that extensively employed in the study of develop probes and chemosensors,because it has excellent light stability,high absorption coefficients,high fluorescence quantum yield,long absorption and emission wavelengths.The spirocyclic forms of rhodamine are generally colorless and non-fluorescent.A prominent solution color change from colorless to pink suggests that the ?-conjugation system of rhodamine fluorophore is largely restored with the target molecular mediated probe recognition reaction.This rhodamine spirolactam scaffold has been exploited by different groups to develop probes and chemosensors for analytes based on the ring-opening mechanism.We present the design,synthesis and application of two kinds of new rhodamine-based chemodosimeter: spirohydrazine rhodamine,nitro-rhodamine B derivatives.The target molecular mediated probe recognition reaction would leads to the ring opening of the spirocycle grouping and thus affords a dual chromogenic and fluorogenic response.These probe of detection performance and mechanism can be analyzed in this paper,and successful be able to fluorescence imaging in live cells.In chapter 1,several fluorescent probes based on spiroring-opening of xanthenes derivatives were summarized.Based on the relevant research,and the objective of this paper were presented.In chapter 2,We have developed a probe by using spirohydrazine rhodamine as a fluorescent chemodosimeter for the selective detection of Cu(II)ions.A rhodamine-based fluorescent chemdosimeter SHR for Cu2+ has been developed based on the spirocyclic ring-opening mechanism.SHR is colorless and nonfluorescent due to intramolecular spirocyclization.Upon incubation with Cu2+ in aqueous media,a highly efficient ring opening of SHR occurs via Cu2+-promoted phenylhydrazine oxidation,causing a dual chromogenic and fluorogenic response.The fluorescent intensity at 580 nm increases linearly with Cu2+ concentration and as low as 10 n M of Cu2+ can be readily detected.The detection limit was calculated to be 2.6 n M(3?).The proposed chemodosimeter shows high selectivity and sensitivity toward Cu2+ over other metal ions and proves to be able to image Cu2+ levels in live cells.In chapter 3,a fluorogenic probe for detection of H2S2 was constructed using nitro group as the recognition unit.We designed and synthesized that replacement of the N,N-diethyl group at the 3 position of rhodamine B by a nitro group afforded a new turn-on rhodamine dye(NC),a desirable compound for the recognition of H2S2.Probe is colorless and nonfluorescent due to the interruption of the ?-conjugation system of rhodamine fluorophore.The nitro group of probe can be reduced by H2S2 to hydroxylamine group,and the ?-conjugation system of rhodamine fluorophore is largely restored with the increase of H2S2 concentration.The fluorescence intensity at 563 nm as a function of H2S2 concentration was recorded,and the observed fluorescence intensity was nearly proportional to H2S2 concentration over the range of 1-20 ?M.The detection limit was calculated to be 0.32 ?M.This is the first example of combined spirocyclic ring-opening reaction with the reduction of the nitro group by H2S2.We observed that the reduction of NC by H2S2 could be proceed under much milder conditions with fast kinetics than other nitro compound,which might be due to the unique spirocyclic structure of NC.These results demonstrate that NC can detect H2S2 with high sensitivity,high selectivity and rapid detection.