Study On The Synthesis And Photophysical Properties Of Polycentric Porphyrin Derivatives

In recent years,the simulation of natural photosynthesis is one of the hot research directions in the scientific community.Among them,the efficient conversion of light energy to electric energy or chemical energy is the goal of scientists.In many efficient simulation systems of photosynthesis,Antenna center compounds have attracted many scientists' interest because of their unique physical and chemical properties.Such compounds contain multiple light harvesting centers,an electron donor(D)and an electron acceptor(A),which can absorb the solar spectrum at all frequencies.Therefore,it has an excellent photoelectric conversion characteristic and it can efficiently utilize light energy.The structure of C60 derivatives,whichare highly conjugated withsmaller reduction potential and lower recombination energy,are excellent electron acceptors(A).Porphyrin compounds have rich ?-electrons and they are the most ideal electron donors(D).They have high stability,strong absorption in the region of visible light wavelength,and they are often used in the D-A system asphotosensitive groups.Compared with porphyrin,tripyridine compounds have strong absorption in the ultraviolet region,and these compounds are easy to synthesize and purify.Their metal compounds are a kind of excellent photosensitizers,and they have been widely used in dye sensitized batteries.In this paper,a series of metal porphyrin-fullerene compounds were synthesized and their photophysical properties were studied,which lay the foundation for the simulation system of photosynthesis.Firstly,in this paper,the corresponding metal zinc porphyrin and hydroxytripyridine are synthesized respectively,Then 1,2-Dibromoethane,1,3-Dibromopropane and 1,4-dibrobutane are used as reactant to synthesize three different chain length linked porphyrin-tripyridine compounds.And the three compounds were fully characterized.At last,three porphyrin-tripyridine compoundswas axially coordinated withthe C60-pyridine derivative C60pyto form threee Antenna center compounds.Then we studied the photophysical properties of the zincporphyrin-tripyridinecompounds and their complexes coordinating with C60py.The results showed that:(1)the apparent fluorescence quenching of the porphyrin end groups in 'Antenna center' compounds showed the electron/energy transfer process between the tripyridine and porphyrin.(2)Fluorescence quenching also occurs after the coordination of porphyrin end groups with fullerene derivatives.It is proved that the electron/energy transfer process occurs between porphyrins and C60py.We continue to study the redox properties ofthese compounds by cyclic voltammetry.The results show that:(1)the reduction potential of C60 has a negative shift compared with the fullerene monomer,which is caused by the decrease of the LUMO energy level by the opening of the fullerene double bonds.(2)the oxidative potential of porphyrin end groups is shifted positively compared with the metalloporphyrin monomers.For the porphyrin end group,there may be ground state interaction,which makes the porphyrin end positively charged and the oxidation potential is positively shifted.Finally,we measured the fluorescence lifetime of three kinds of Antenna center D-A system compounds by transient fluorescence technique.The charge separation rate constants are calculated according to the fluorescence lifetime.According to the accurate results,we have confirmed that the charge separation state of ZnTpp[(CH2)4tpy]4:C60py is the longest among three complexes.