Properties Of Ortho-Functionalized Perylene Diimide Derivatives

Due to their rigid conjugate plane structures,perylene diimide derivatives have a number of unique features such as good photochemical and thermal stabilities as well as high fluorescence quantum yield,and are easily modified.Their applications in light-emitting diodes,organic field-effect transistors,biomedicine sensors,conjugated porous polymers,molecular probe and a variety of optoelectronic devices have been extensively studied.Nowadays,more and more attention has been focused on the modification of PDI derivatives to modulate their chemical and physical properties.It has been shown that introducing different substituents in the N-position can only change the solubility and aggregation of PDI derivatives.On the contrary,bay-substitution helps tuning both the absorption,fluorescence and LUMO/HOMO of PDI derivatives.However,it usually renders the compounds highly twisted,which may adversely impact molecular packing and film morphology.By virtue of the favorable balance between the ?-? stacking,energy levels and solubility,ortho-fnnctionalization opens a route to a new generation perylene diimides and provides a way to improve the electrochemical properties of PDI derivatives while at the same time retaining the planarity of the core.For this reason,ortho-functionalized PDI derivatives represent a class of promising high-performance rylene dyes for tomorrow's applications.This dissertation consists of the following five chapters:In chapter 1,the chemical and physical properties of PDI derivatives are summarized and the applications of ortho-substituted PDI derivatives in solar cell,porous conjugated polymer and organic solid-state laser are summarized.Finally,we present the working assumption of this thesis.In chapter 2,the optical electronic and self-assembly of a range of 2,5,8,11-tetraalkenyl-substituted PDI derivatives were investigated.Compared with the parent unsubstituted PDI derivatives,introduction of ortho-tetraalkenyl groups not only increased the solubility but also lowered their LUMO levels.Interestingly,the packing models were changed from OD to 1D due to their enhanced ?-? stacking interactions.In chapter 3,the influences of different functional groups on the electronic,photophysical,and redox properties of a range of ortho-substituted PDI derivatives were investigated by UV-vis spectrophotometry,fluorescence spectroscopy and cyclic voltammetry.The results showed that the fluorescence and HOMO/LUMO levels of PDI derivatives were easily tuned by the introduction of OR,NHAr,CN,alkynyl and aryl groups.Moreover,rather small alterations of the ortho-substituents could result in extremely different optical features.In chapter 4,the electrochemical and optical properties of several ortho-?-extended PDI derivatives were studied.The results showed that by modifying the topology,number,position,and valence state of different heteroatoms in the ortho-?-extended PDI system,it is possible to regulate and control their key optoelectronic features,including the band gap,optical absorption spectra,photoluminescence,and redox behavior.In chapter 5,the atropisomers of ortho-?-extended PDI derivatives were observed.In addition,stable chiral radical anion can be obtained when F-was added in their tetrahydrofuran solution.