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Synthesis And Photophysical Study Of Viscosity Molecular And Thiol Fluorescent Probes Based On Tuning Singlet Effect Of Fluorophores

Posted on:2012-10-07Degree:MasterType:Thesis
Country:ChinaCandidate:J Y ShaoFull Text:PDF
GTID:2131330335454323Subject:Fine chemicals
Abstract/Summary:PDF Full Text Request
Singlet excited state regulation is very important for the regulation of the fluorescence emission. Photophysical properties of molecules, such as the absorption wavelength, emission wavelength, Stokes shift can be regulated by reducing or increasing the energy levels of the singlet excited state. Viscosity of fluids is an indicator of liquidity, its'change is related to many diseases; Thiol compound is an important component of the organism, intracellular thiol concentration changes is also related to a number of diseases. It is very important to design viscosity probes and thiol compound probes with high sensitivity and excellent photophysical properties through single-state regulation in the study and prevention of disease.The molecular rotors are a class of viscosity-sensitive fluorescent molecules. The reported fluorescent molecular rotors suffer from some disadvantages:(1) molecular structures are very limited and rare derivatization has been reported; (2) shorter emission wavelength and small stokes shift. In order to address these drawbacks, firstly we designed two viscosity probe c-1 and c-2 based on the fluorophore of coumarin. These two rotors are following in the classical rotor model:electron withdrawing is directly connected to the fluorophore, which causes strong intramolecular charge transfer effect. Red-shifted emission wavelength was observed for the rotors, and at the same time the absorption wavelength was extended to the red-end of the spectrum, but the Stokes shift is not increased. Based on the classical rotor model, we designed r-3 to r-9 that insert thiophene between fluorophore and electron withdrawing part. Because thiophene takes planar toward the molecular backbone, so it can increase the level of the conjugation of the rotor molecules, thus the introduced thiophene can not only increase the absorption wavelength and emission wavelength, but it can also enlarge Stokes Shift. We also explain the effect of the introduction of thiophene in increasing absorption wavelength, emission wavelength, Stokes shift effect, the Stokes shift by the use of Gaussian 09, the increase of the Stokes shift is a result of adjustment of excited state configuration. Finally, we successfully use our probe in the application of indicating liquid crystal from a liquid to liquid crystal phase transitions. Thiols compounds, such as cysteine, glutathione and peptides/proteins, are found in more complex in vivo environment. Molecular probes for selective detection of thiol compounds have attracted much attention. However, the excitation/emission wavelength of the thiol probes is usually short. Short excitation wavelength will cause damage to biological tissues, so it is necessary to devise thiol probes that show strong absorption in visible region, long-wavelength emission and large Stokes shift. Boron-dipyrromethene (BODIPY) shows strong absorption of visible light and it is easy to de modified, so we designed a fluorescent thiol probe t-1 based on BODIPY. The probe shows red emission in the presence of thiols such as cysteine. But it has a small Stokes Shift, so we designed fluorescent probe t-2 based on fluorescence resonance energy transfer (FRET). The two probes have a very good selectivity to cysteine. We rationalized the off-on switching effect of the probe by theoretical calculations (DFT), and we also investigated the FRET mechanism by the use of DFT/TDDFT.
Keywords/Search Tags:Singlet excited state, viscosity, thiols compounds, molecular probe, thiophene, BODIPY
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