| Among the numerous classes of highly fluorescent dyes,the set based Aza-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene(aza-BODIPYs)dyes shows perhaps the highest potential.The many excellent features of aza-BODIPY can explain its ever-growing success,such as,the robustness against light and chemicals,the relatively high molar absorption coefficients ?(?)and fluorescence quantum yields?F,narrow emission bandwidths with high peak intensities,excitation/emission wavelengths in the near-infrared region(>650 nm).The wide versatility of synthetic pathways to the aza-BODIPY class of fluorophores allows the creation of a perfect fit between the structure of the dye and its desired spectroscopic and photophysical characteristics.So the possible uses of aza-BODIPY-based dyes for fluorescence indicators for detection of heavy-metal ions,biological labeling and photodynamic therapy were fully recognized.Different from organic fluorescent dyes,Quantum Dot(QD)properties of interest to biologists include symmetric photoluminescence(PL)spectra spanning tuned from the UV to the infrared(IR)region of the spectrum by changing their size and composition has led to promising applications in diagnostic(cellular labelling,deep-tissue imaging,assay labelling).However,the organic/inorganic fluorescent dyes all have their own limitations in the performance.Heavy-atom-functionalized BODIPY dyes have been reported which exhibit enhanced rates of intersystem crossing(ISC)and hence higher singlet oxygen quantum yields.However,this represent a bottleneck that the BODIPY can not be used for both the fluorescence imaging and the photodynamic therapy(PDT)at the same time since the efficient ISC will quenched the highly fluorescent.But the therapeutic modalities of bare/simple metal-based QDs so far been fundamentally limited due to their toxic effect in live cells and the low selectivity for tumor,which was used for neither photodanamic therapy nor hyperthermia treatment effect.Hence,a theranostic strategy that permits the concurrent imaging and photodanamic therapy would also be complemented though FRET by the use of QDs high quantum yield and size-control fluorescence emission,a combination of aza-BODIPY's photodynamic therapy effect.Azobenzene(1,2-diaryldiazenes)has been focused of intense research since it was first reported by Alfred Nobel in 1856,which have a unique place in the field of photoresponsive conjugated molecules as their reversible E/Z photoisomerization.However the absorption wavelength of azobenzene in the UV/visible light regions,most of the research reported the structural modification azobenzene molecules,which can produce light induced isomerization under visible light irradiation.But without absorption in near infrared region,the application of the biomedical field is limited.We will try to conjugate the azobenzene and other molecules to form complexes,in order that it has a larger increase in performance.Porphyrin,as a highly conjugated photoelectricity functional molecules with?-electronic structure,determines it can obtain the supramolecular structure by use of?-? stacking interactions,hydrogen bond,coordination bond,electrostatic interaction,hydrophobic interaction and intermolecular forces.Numerous azobenzene-linked porphyrin compounds within the xy-plane of the porphyrin ?-system have been reported,in this type of compounds,the azo group behaves as an electron attracting group and affects the electronic environment of the porphyrin ring,which causes the change in the absorption spectra of the original porphyrins.These intramolecular electronic communication between azobenzene group and porphyrin units,however,may cause loss of the ordinal feature of azobenzen,such as isomerization property.So the purpose of employing novel conjugates comprised of azobenzene and porphyrin as an axial ligand through an sp3 hybridized linker unit is to study the isomerization.This kind of rigid ?-plane conjugates,with the unique controled structure,photoelectric properties and self-assembly behavior,as the basis of molecular materials and molecular devices,will promote the development of organic functional materials.The major results are summarized as follows:1.We successfully design and synthesize a series of thiophene-substituted boratriazaindacenes(aza-Bodipy's)A1 and A2 with long wavelength absorption and emission due to the extension of the ?-system.In addition,the "turn-off'fluorescence responses and solution color changes selectively toward mercury ion would be allow ratiometric sensing based on PET mechanism.2.QDs-aza-BODIPY@FA-DSPE-PEG2000 congjugate was synthesized using novel self-assembly conjugation strategies.A2 bind to the surface of the tailored QDs,which appears that the value of the smallest center-to-center separation distance in combaination with the large the spectral overlap value lead to the high FRET efficiency(Eff=90%),resulted in a large decline of the QDs fluorescence emission accompanied by stimulated fluorescence emission of A2 at low concentration with 10-7 M.The conjugates with relatively efficient FRET processes could be tailored for different applications in theranositics strategy.By excitating the QDs at 635 nm because of the high absorption cross sections of QDs,For instance,the increase fluorscence emission of aza-BODIPY may be used for cell fluorscence imaging.Moreover,the PDT efficacy may increase significantly observied by confocal fluorescence imaging and MTT date identifying apoptotic cells.3.A facile synthetic of unilateral and bilateral of novel orthogonally arranged conjugates comprised of rhodium(?)tetrakis-4-tolyporphyrin and paraiodoanilinelinked by a covalent Rh-C(aryl)bond is described.The unique azobenzene structure facilitates N=N bond protonated in the presence of trifluoroacetic acid(TFA)in toluene,leading to the azobenzene moiety transformation from trans to cis form.Simultaneously,the Rh?(ttp)-azobenzene radical is labile to form ?-?conjugated dimer to get the more stable configuration,resulting in sharp color change from orange-yellow to modena.This chromogenic process can be reversed by adding trace amount of base or proton-accepting solvents.1H-NMR study,as well as IM-MS and EPR date suggest that TFA-induced N=N bond cleavage and protonated may forming the whole ?-conjugation of the porphyrin dimer,resulting in significant configration transfer and colorimetric behavior. |
PDF Full Text Request