Photophysical Properties And Light Induced Oxidative Degradation Of Metalloporphyrin-arylimidazole Dyads

Porphyrin have displayed unique photophysical properties and electrochemicalproperties, and its structure is stable and easy to modify. Optical and electricalproperties of porphyrin have been improved via peripheral functionalization at the β-and meso-positions. As a particular imidazole derivates, Triarylimidazole show ahighly conjugated structure, which is similar to porphyrin. Such imidazole derivatesshow a wide application in many yields, such as optical materials, chemiluminescenceand fluorescence probe， which is ascribed to their efficient electron-transportcapability and strong electron-donating ability, as well as unique chemiluminescenceand metal ion-based fluorescence quenching.If arylimidazole is introduced into porphyrin to form porphyrin-arylimidazoledyads, these dyads might display the improved optical properties compared to pristineporphyrin, and show some other novel performance. In this thesis, three types ofmetalloporphyrin-arylimidazole dyads were synthesized with different connectionsbetween metalloporphyrin unit and arylimidazole unit. The studies for these dyadsfocused on their photophysical properties and structural stability. The specificcontents are as follows:(1) Three types of conjugated and unconjugated metalloporphyrin-arylimidazoledyads were synthesized via Debus-Radziszewsk and Williamson etherization reaction,respectively, and structurally characterized by1H NMR, MALDI-TOF MS and FT-IRspectra.(2) Photophysical properties of these dyads were studied systematacially usingUV-vis spectra and fluorescence spectra. The absorption spectra indicated that therewere no electronic interaction between porphyrin unit and arylimidazole unit in thesedyads. The fluorescence spectra indicated that energy transfer behavior only existed inunconjugated dyad.(3) The redox potential of the two copper coordinated conjugatedporphyrin-arylimidazole dyads were investigated by cyclic voltammetric studies,which revealed that the dyads were more difficult to oxidize compared to the pristinemetalloporphyrins.(4) The light induced oxidative degradation products of these dyads were studiedby MALDI-TOF MS. The effects of metalloporphyrins as well as connections between porphyrin unit and arylimidazole unit on the oxidative degradation rate ofthese dyads were also studied by UV-vis spectroscopy. The results indicated that thecopper coordinated dyads remained relatively stable upon light irradiation, while zinccoordinated dyads were easy to cause arylimidazole unit to degradate, in which theunconjugated dyad showed the fast degradation rate.