The Research On New Functional Fluorescent Dyes Based On Naphthalimdes And Rhodamines

The naphthalimides and rhodamines have had great attention because of their good photochemical and photophysical properties.Naphthalimides had large potential application market in various fields,so it was a chance and a challenge for us to develop more functional derivatives of naphthalimide with better properties.Since the extentisively appilication of rhodamines in bioliogical environment,it was necessary and urgent to develop more kinds of such long wavelength rhodamine derivatives to meet the increasing demands.In this work, three kinds of fluorescent sensors based on naphthaiimdes and one kind of silicon-substituted rhodamine dyes with long absorption and emission wavelength had been synthsized.1.The new PET fluorescent proton sponges-A1,A2 and A3 had synthesized based on naphthalimides.DMAN was proved a good proton receptor unit to develop sensitive fluorescent switches triggered by lower-concentration proton.A3 exhibited significant fluorescence enhancement upon protonation in high pH(pH=12.9) aqueous solutions,the pKa of which was 11.The lowest detection concentrition was 1.25×10^-13 mol/L.2.Based on the approach of switching off FRET by wrecking the acceptor part, cassette-type sensors(SN-1,SN-2 and SN-3) for fluoride anion containing naphthalimide and squaraine units has been developed.These sensors show sensitive response to fluoride anion through both naked-eye detectable colour changes and ratiometric fluorescence changes.The detection process was realized by the combination of the reactive recognition and FRET mechanism.SN-2 and SN-3 showed excellent ratiometric fluorescence changes which made the quantitive measurement to be avaliable.The detection limit and equilibrium concentrion of F^- for SN-2 was 2μM and 1.2 mM with short reaction time(3min).The detection limit and equilibrium concentrion of F^- for SN-3 was 1μM and 50μM with the reaction time about 30min.3.Two chiral fluorephores NNH and NNM had been synthesized by introducing the chiral center into 4-position of the naphthalimide.NNH can be used as the mandelic acid sensor.The absorption and emission of NNH blue shifted 12 nm with the addition of the D-mandelic acid,as same time the emission increased to 1.2 flod.The absorption and emission of NNH had no changes with the addition of L-mandelic acid.The NNM can be used as pH sensor by fluorescent emission and circular dichroism properties,the pKa caculated by the two menthods were 8.5 and 8.8 respectively,which machted very well.It proved that circular dichroism could be used as a reasonable method for NNM to detect the recognition of pH.4.Two new strong fluorescence silicon-substituted rhodamine dyes TMDHS and TMDPS,in the red region had been developed through substitution of rhodamine's oxygen bridge atom by silicon.Such a small structural change resulted in a 90 nm red shift.The absorption wavelength of the two compounds was at 641 nm and 628 nm respectively.The emission wavelength of which was at 659nm and 664nm respectively.As we known,this was the first case that silicon atom was adopted as the functional element into the key position of a conventional excellent dye to successfully modulate the spectral properties.The electrochemical and the theoretical computational studies indicated that the smaller energy gap of TMDHS resulted from both energy decrease of LUMO attributed to specialδ^*-π^* and energy increase of HOMO attributed to the electron donating ability of silicon atom.