Synthesis Of Light-harvesting Materials Based On Perylene Bisimide: Photo-induced Energy And Electron Transfer

Photoinduced energy and electron transfer processes play a crucial role in natural photosynthesis. On its way, light-harvesting complexs absorbed photons subsequent transport energy through excited-state energy transfer to the photosynthetic reaction centers where it initiates a multistep electron transfer reaction in which the captured energy is converted into chemical energy. Recent research has focused on the synthesis of bichromophoric or multichromophoric dyes in order to develop new artificial light harvesting antennae to mimic the functionality of natural light harvesting systems. Perylene bisimide (PBI) dyes, which are of high fluorescence quantum yield, redox properties, chemical, thermal and very high photochemical stability and easily substitution in the bay and imide area, are of increasing interest for application in constructing lighting harvesting arrays as energy acceptor because which will likely to be more functional features. In this thesis, design and synthesis a series of light-harvesting systems contain 1,8-naphthalene imide and perylene bisimide based on the literature review, investigated the photophysical and photochemistry process by several spectroscopic techniques. The details are summarized as follows:1. Photophysical properties in a novel light-harvesting array, consisting of four appended 1,8-naphthalene imide(NI) attached to 1,6:7,12-positions of perylene-3,4:9,10-bis(dicarboximide)(PBI), have been investigated by absorption and fluorescence spectra. It was revealed that compared to model compounds, this light-harvesting array exhibited 10.7-fold high antenna effect, whether in dichloromethane or toluene. The results obtained further demonstrated that the NI component as light-harvesting antenna transferred the absorbed energy to the acceptor PBI fast and no electronic transfer processes completed with energy transfer processes. The results show that this array can transforms UV directly to IR radiation and is an efficient way to construct antenna systems.2.Second, design and synthesis 1,8-naphthalene imide as periphery functional unit and perylene bisimide as core one generation (G1-a1、G1-a2、G1-b1、Gi-b2), two generation (G2) melamine dendrimer based on supra reseach. UV-vis spectra shows no strong interaction between two chromophore moieties in the ground state. Dendron 2a has isomerism, the fluorescence of it was quenched in dichloromethane but the fluorescence was restore in toluene. The fluorescence spectra of dendron 2b in dichloromethane and toluene shows a clear vibronic structure emission maxima at 379 nm and intramolecular excimer emission. The results by investigated the dendrimers shows that 1,8-naphthalene imide transferred the absorbed energy to the acceptor PBI fastly and preventing non-radiative fluorescence decay and excimer take place between 1,8-naphthalene imide. The core emission relative to model compound in G1-a1、G1-a2、Gi-b1、G1-b2、G2 was 6、7.4、6.04、6.16、9.43-fold in dichloromethane respectively,6.04、5.08、2.77、3.03、4.2-fold in toluene respectively. The results obtained further demonstrated that fast energy transfer process between two chromophores dominant over all photophysical and photochemistry process.3. In order to further study photophysical mechanism in light-harvesting systems based on this two chromophores, design and synthesis dendrimer 1、2, where 4-alkoxy-1,8-naphth-alimide with high fluorescence quantum yield as periphery functional unit and perylene bisimide as core. Two dendrimers shows excellent Light-harvesting performance. In dendrimer 1,4-alkoxy-1,8-naphthalimide as light harvesting antennae, transport energy through excited-state energy transfer to the perylene bisimide energy receptor, subsequent non-radiative excited state electron transfer take place. The core emission relative to model compoundwas 16-fold in dichloromethane of dendrimer 1. In less polar solvent such as 1,4-dixaone, the energy of the charge-separated states is substantially lifted which preventing non-radiative electron transfer, the core emission relative to model compound was 24-fold. In dendrimer 2, tertiary amine as new electron donor take part in non-radiative photo-induced electron transfer, reduced the fluorescence of perylene bisimide intensely, so the core emission was 9.6-fold in dichloromethane. This results have important guide significance and reference value with regard to further construct new light-harvesting materials and frequency converters.