Design, Synthesis And Application Of Re(Ⅰ) And Ru(Ⅱ) Complexes Based On MLCT Emission

In the past few decades, A lot of experimental and theoretical studies have been done on low metal to ligand charge transfer (MLCT) excited state. Transition metal complexes based on MLCT emission have many advantages, such as good photo stability, large Stokes shifts and long fluorescence lifetime. Application of d6 transition metal complexes, Ru(Ⅱ)、Os(Ⅱ)、Re(Ⅰ)、Ir(Ⅲ) polypyridine complexes are most widely used in the fields of photoelectric conversion, supramolecular self-assembly and the fluorescent probe. The thesis was carried out around design, synthesis of transition metal complexes based on MLCT emission, and their application in cell imaging and chemosensor. The thesis consists of five chapters.1, It has been outlined of the basic process of photochemistry and photophysics. Applications of transition metal complexes based on emission have been reviewed in the fields of photochemical sensor and biology.2, Ligands (L1, L2, L3, L4 and L5) and corresponding Re(I) complexes (Re-A, Re-B, Re-C, Re-D and Re-E) based on MLCT emission have been synthesized and characterized. Their photophysical and spectroscopic properties were studied. These complexes show excellent hydrophobic properties which gained by computation. The core-shell nanoparticles (F-A, F-B, F-C, F-D and F-E) are prepared by encapsulating the complexes with amphipathic copolymer F. The prepared nanoparticles F-B were selected as an example to study its appication in biological imaging and gene transfection. As a result, the nanoparticles were also used as a bifunctional agent for simultaneous cell imaging and gene transfection. Our research establishes a new method to construct bifunctional nanoparticles by encapsulating transition metal complexes with amphiphilic copolymers for cell imaging and gene transfection. The work of the chapter has been published in Chemical Communications (Chem. Commun.,2009,6759-6761).3, A ligand [4’-methyl-2,2’-dipyridine-4-carboxyl]-N’-Phenylthiosemicarbazide (L6) containing thiosemicarbazide moiety has been successfully synthesized from the 4-methyl-pyridine. Then, a Ru(II) complex Ru-G based on MLCT emission was synthesized from the prepared ligand. In the presence of Hg2+,the 1MLCT absorption shifted from 480 nm to 430 nm and increased slightly. Fluorescence intensity increased more than 2.7-fold as compared to complex Ru-G alone. The color of Ru-G solution changed from brown to yellow which can be judged by naked eye. In addition, there is no significant change of absorption and fluorescence spectra for Ru-G in the presence of other cations, such as Cu2+, Pb2+, Cr2+, Ni2+, Fe3+, Co2+, Cd2+ Zn2+, Mn2+, Mg2+ and Ag+. Complex Ru-G has a great potential to be used as a highly selective and sensitive luminescence chemosensor for Hg2+4, Ligands L7、L8 and L9 were synthesized and Re(I) complexes (Re-H, Re-I, Re-J and Re-K) based on MLCT emission have been synthesized and characterized. Among these Re(I) complexes, significant enhancement of fluorescence intensities and absorption with a 30 nm blue shift based on MLCT revealed the sepecific interaction between Re-H and Cys or Hcy. Re-H has a great potential to be used a good sensitive luminescence chemosensor for Cys and Hcy.5, Conclusions and achievements of the thesis.