Research On Synthesis And Properties Of Novel 3H-indolenine Fluorescent Cyanine Dyes

Cyanine dyes have been widely used as fluorescence probes for biosystem in biomolecular analysis field duo to their large molar extinction coefficient, broad absorption spectra and wavelength tunability. Recently, more and more research has been focused on the application of cyanine dyes as photovoltaic material. However, the tendency to undergo photodegradation becomes the most common problem in irradiation, which are disadvantageous for long-term storage. Therefore the investigation on the photostability of cyanine dyes possesses the main significance in biomolecular analysis field.To study the effects of substituents on the rate of dyes photofading, 7 novel near-infiared heptamethine cyanine dyes with different electron-donating or electron-withdrawing substituents on N-position of 3H indolenine ring have been synthesized in this article. Photoreaction experiment was carried out irradiated with a 500W I-W lamp. Photofading behaviors of the dyes were investigated through determining the change of the maximal absorbance of the dyes. The results show that the dyes with electron-donating group on nitrogen atom of 3H indolenine ring perform the decreased photofading rate and the improved photostability compared with the dyes with electron-withdrawing group. The ability of the electron-donating or withdrawing bears the good correlation with the photostability of the dyes. The certain comparison of carboxylbenzyl and pentacarboxyl substituted dyes was obtained through photoreaction experiment And the photofading rate of the latter is double than mat of the former. Explanation was shown about the difference of the photofading process using cyclic voltammetry experiment The results show that the redox reaction of losing one electron for the electron-donating substituted dye is chemically reversible. The dye moiety was destroyed after losing two electrons. But the redox reaction of losing one electron for the electron-withdrawing substituted dye is chemically irreversible, and the dye moiety was destroyed after losing one electron. To investigate the mechanism of the photofading, Photodegradation experiments were carried out in methanol and deuterated methanol. The results show that the ratio of the rate constant in deuterated methanol compared with that in methanol is 62, which is far below 20, the ratio of the lifetime of singlet oxygen in deuterated methanol compared with that in methanol. Therefore the photodegradation route not only goes along with the singlet oxygen mechanism, but also follows the superoxide mechanism. Depending on the photofading route ofsimilar cyanine dye reported in previous literature and make HPLC-MS analysis to the residue of three cyanine dyes, the possible photorading route was deduced.Five novel water soluble and insoluble pentamethine cyanine dyes were synthesized with carboxylbenzyl group. The design of the structure and the purification are optimized. Gram level of purified dye with mono-carboxyl group is obtained through positive silica gel chromatogram and recrystallization from water, which exhibits the potential application as probe of oligonucleic acid and protein activated by the iV'-hydroxylsuccinimide. The photofading experiment was carried out among the pentamethine cyanine dyes with asymmetric and symmetric substituted groups on Apposition. The results show that the photostabilities of the asymmetric dyes is more excellent than that of symmetric dyes. The introducing of benzyl and ethyl groups on N-position enhances the stability of the dyes obviously. In addition, introducing of carboxyl group on N-position is not favorable to increasing the photostabilities of the dyes.Presently, the main problem of the cyanine dyes as sensitizers tor the DSSC is the low photoelectric conversion efficiency. So novel cyanine dyes are necessary to be synthesized. To investigate the effect of sensitizers on the photoelectron conversion efficiency, novel trimethine cyanine dye and squarylium dye with high photostability were synthesized and used as sensitizers for DSSC. The results show that Isc (2.76mA/cm2), IPCE (46%) and tj (1.7%) of TiC>2 nanocrystalline solar cell sensitized by squarylium dye perform preferable values than that of T1O2 nanocrystalline solar cell sensitized by trimethine cyanine dye when the TiC>2 nanostructured porous film was 6.5um thick and was sensitized for 6 hours and 4 hours respectively. Several reasons were considered to lead to the different photoelectric properties of the two T1Q2 electrodes sensitized by the two dyes. Firstly, spectrum range of squarylium dye shifts to the long wavelength region, which is favorable to absorb solar light Moreover, the lowest excited energy level of squarylium dye matches well to that of T1Q2 nanoparticle conductive band gap. And the photoisomerization is one of the major decay pathways for methine dyes, squarylium dye with methine chain substituted by squaric acid ring reduces cis-trans isomers. It is favorable to form ordered orientation on TiQ? surface so as to increase the electron injection efficiency obviously. Moreover, the J-aggregated dyes on TiO2 surface and the effects on the photoelectric properties of the electrodes were discussed.Different aggregation of cyanine dyes in DMF-water solvent were investigated and the effect of electrolyte, solid medium, concentration of the dyes were studied. The hydrophobic action is the driving force to aggregate. The molecular structure, solvents, solid interface are the main factors to lead to aggregate.