Tuning The Spectroscopy Of Stilbene Derivatives Dyes Based On The Intramolecular Charge Separation

Novel organic dyes have recently been investigated extensively due to their broad applications such as in biomedical, photoelectronic material. Hence, to study the effect of chemical structure of organic dyes on absorption and emission spectra is of far-reaching significance in photophysical and photochemistry field. Thus the regulation of molecular levels by molecular controlling the photophysical properties of dye molecules has become the research focus recently.This thesis mentions that the different linkage could lead to various intramolecular charge separation, and which affect the photochemical properties of dyes. Stilbene-like dye is one of the most important classes of dyes, which exhibits exceptionally large two-photon effects, and it possesses nonlinear optical properties. As nitro-stilbene is a sort of fluorescent material with appliantion value, by introduced different groups, series diethylstilbestrol dyes were designed and synthesised. And the reliable experimental evidence for turning the luminous nature of the compounds at molecular level was got. The concrete work is listed in the following:1. Design, synthesis and characterization nitro-stilbene molecularA series of stilbene were designed and synthesized by altering the electron donor, and all these compounds have been characterized by 1H NMR spectra, 13C NMR spectra, elemental analyses and DAT etc.2. Linrar and non-linear propertiesThe UV/vis absorption, ?uorescence, ?uorescence quantum yields in various solvents and ?uorescence lifetimes were measured, The conclusions were listed as following:â‘ The absorption at long-wavelength was determined intramolecular charge transfer(ICT). Along with different donor-withdrawing electronic system, the target molecules showed distinct photochemical properties.â‘¡Intramolecular electron density distribution due to the solvent polarity. the maximum fluorescence peaks clearly show a slight red-shift with the increase of the polarity of the solvent, meanwhile, the compound quantum yield of fluorescence and fluorescence intensity were raised in varying degrees.â‘¢The two-photon up-conrersed fluorescences and two-photon absorption cross-section were determined. The experimental results indicated that the two-photon absorption cross-section enhancement with the increasing the dimensionality of molecule. The maximum fluorescence peaks show a slight red-shift with the increase of the polarity of the solvent.3. Electrochemistry and thermal analysisCV tests showed that all the compounds by characterized with irreversible redox processes. The redox processeses of all the compounds were dominated by diffusion- controlled electron transfer reactions resulting from linear increasing of peak currents with the square root of scan rates. Ester bond as an electron-withdrawing group could undergo as well, so the compound by ester bond connecting occurred more reduction process than ether bond connecting. The DTA-TGA showed that the linkage didn't play a key role for thermal stability of nitro-stilbene derivatives.