Containing Pyridine, Bipyridine Side Groups Of The Organic Phosphazene Polydentate Ligands, Structural Characterization And Spectroscopic Properties Of Study

Directed by professor Fu Wen-fuPhosphazenes bearing aryloxy side groups are materials with interesting properties, for example, they exhibit biomedical properties and promising applications, have second-order nonlinear optical properties, and might find application as liquid crystals or as photo-active materials. In all applications, their properties depend on the substituents linked to the aryloxy rings. The photochemical and photophysical properties of Pyridine, Bipyridine and their derivertives continue to receive considerable attention. This is largely due to the potential applications of these chromophores in diverse areas such as solar energy conversion, luminescence sensing, electroluminescence displays and photochemical molecular devices. Due to the structural versatility of the polypyridyl ligands, the excited-state properties of their transition metal complexes can be modulated to a great extent. In this dissertation, we synthesized a series of Phosphazenes bearing polypyridine ligands side groups and studied the effects of the ligand structure on the photophysical properties of them. Some ligands exhibit potential applications in cation recognition and detection as chemical sensors:1. We designed and synthesized four new phosphazenes bearing pyridine , bipyridine side groups L1 to L4. their structures had been determined by IR,'HNMR, 31PNMR, TOF MS, and Element Analysis, and their structures also can be inferred from the UV-Vis , emission and excitation spectra. We find that these new compounds are conform with what we have designed.2. These compounds themselves have strong solid state fluorescent emission with high quantum yield. For example, L3 and L4 solid state of the two ligands themselves are luminescent with the peak maximum at 514nm and 528nm far upon excitation at 340nm at room temperature. Up to now, photo-luminescent property of cyclotriposphazenes has not been found in the literature.3. [N3P3C16] is photo transparent and there is no absorption from 200nm-800nm, the shape and the position of the absorption band of L1 to L4 are influenced mostly by the side groups, their properties depend on the constituents linked to the aryloxy rings.4. Their absorption and fluorescence emission properties depend strongly on the PH changes and the prescence of metal ions, particularly zinc ion. These changes are indicative of a strong charge-transfer interaction in both the ground and the exited state between the hydroxyphenone connected to the cyclotriphosphazene bacebone and the protonated (or complexed) bipyridine, due to the protonated (or complexed) bipyridine formation. These new legends undergo very large red shifts in their fluorescence maxima when the solvent is changed from the non-polar solvent to the polar ethanol due to the involvement of ICT transition. Upon addition of metal ions, particularly Zn2+, the absorption and emission spectra of the four ligands experience great changes. Fe2\ Cu2\ Cu\ Ni2\ Cd2+and Pb2+ ions only result to the extinguish of their emission spectrums. But Ca2\ Mg2+ and Hg2+ ions have none effect to the spectrum of these four ligands. The strong binding affinity and high selectivity make them attractive for application as fluorescence sensors for Zn2+.