The Study Of Unsymmetrical Diarylethenes Based On A Phenanthroline Ligand

In recent years, the fluorescent sensors with instantaneous response and high sensitivity have gained a lot of interest, which can be potential applications in medical, environmental, and biology. In many senors, the colorimetric sensor has been extensively investigated because cation recognition requires changes in the absorption spectra along with corresponding color changes which can be detected by the ’naked eye’. As a member of organic photochromic compounds, organic diarylethenes are become one of the most promising candidates for photoelectric material owning to their notable thermally irreversible photochromic behavior and remarkable fatigue resistance. They can be potential applications in photoswitchable molecular devices, logic circuits, and chemical sensors. Currently, the new groups have been incorporated into the photochromic dithienylethene unit with a view to optimizing the photochromism and giving rise to some novel properties, which are hotspots in this filed.The introduction of phenanthroline groups at the end of aromatic aldehyde expect better modulation the photochromic properties of the diarylethenes is the focus of this thesis research. The substituent, acid or ion effects on their optoelectronic properties were investigated in detail. The main contents and results are generalized as follow:In this thesis, ten asymmetrical photochromic diarylethenes based on phenanthroline groups were synthesized. Their structures were characterized by NMR, elemental analysis and IR.Photochromic properties of these diarylethenes in different medium such as in solutions and PMMA films were studied. The result shows that the compounds DT-5-9and DT-12-13are exhibited good photochromic properties in methanol solutions, and the compounds DT-10-11and DT-14are exhibited good photochromic properties in both chloroform solutions and PMMA films.The fatigue resistance and thermal stability were studied. The conclusion exhibited that all of the diarylethenes had good thermal stabilities at room temperature and78℃. As compared to the parent aldehyde compound DT-1, the fatigue resistance of the imidazolyl-containing compounds DT-5-6were slightly increased; The fatigue resistance of diarylethenes based on phenanthroline unit DT-11in solution was much better than that in solid medium; The compounds DT-12-13had good fatigue resistance in solution.The substituents and the length of the conjugated chain have notable effects on the properties of these diarylethenes were investigated in detail. Among these two derivatives DT-5-6, the diarylethene with a phenanthroline moiety (DT-6) had the bigger absorption maximum both for its open-ring and closed-ring isomers, but the molar absorption coefficient and the photoconversion were decreased significantly. The emission intensity of DT-5-6was much stronger than that of DT-1, indicating that the emission intensity of diarylethenes with an imidazole group was enhanced significantly. For the derivatives DT-6-8, compared with the parent diarylethene DT-6, which terminal benzene ring has no substituents, The substituents effect results suggest that no matter replacing the hydrogen atom at the para-position of the therminal benzene ring with electron-withdrawing substituent or electon-donating substituent the molar absorption coefficient of the diarylethenes had clearly increased. When the terminal benzene ring has electro-withdrawing substituent, the fluorescence intensity and fluorescence modulation efficiency increased. For the compounds DT-8-9and DT-12-13, the absorption maximum for closed-ring isomers of the long π-conjugated chain containing compounds DT-9and DT-13significantly less than the compounds DT-8and DT-12, but the cyclization quantum yield and the photoconversion ratio exhibited a reverse trend.The ion respond was studied. Upon addition of Cu2+to the closed-ring compounds DT-5C-8C and DT-12C, the absorption maximum were blue-shifted and then decreased gradually accompanied with a notable color change from blue to purple and then eventually become to colorless. Meanwhile, the compound DT-5C exhibited high selectivity towards Sn2+, Al3+, and Cr3+with significant fluorescence change. Another, upon addition of Cu2+to the closed-ring compounds DT-9C and DT-13C, the absorption maximum were decreased gradually accompanied with a notable color change from blue to colorless. And the fluorescence intensity of the two compounds was increased significant with the addition of Ca2+, Mg2+, and Sr2+.The effects of acid were studied. The absorption maximum bathochromic shifted from546to552nm when addition of TFA to the close-ring compound DT-11C accompanied with a notable color change from from magenta to slateblue. The slateblue solution either returned entirely back to magenta after neutralization with the TEA. Another, the emission peak of compound DT-11O hypochromatically along with the addition of TFA and its intensity increased significantly, but addition enough amount of TEA to the compound DT-11O, a high-fluorescence quenching efficiency was achieved. No matter adding of TFA or TEA to the compound DT-10O, the fluorescence intensity was decreased significantly.The optoelectronic properties of zinc ion complex were studied. The synthesis of the complex opened up a new path for the diarylethenes.