Synthesis And Optical Properties Of N,N’-2-replacement Bay Disubstituted Perylene Diimide Derivatives

Perylene diimide(PDI)derivatives each have two imide rings in its molecule structure,which usually gives this kind of molecules a strong electron affinity.In recent years,through the functional modification,PDI and its derivatives,as the acceptor material of the organic semiconductor,are widely applied into all kinds of aspects in the field of optical and electronic materials such as organic solar cells(OPC),organic electroluminescent(OLED)and fluorescent probe,etc,and become the research hot spot.In this research,a series of perylene diimide derivatives were synthesized using N,N’-di-substituted-1,7-di-substituted perylene diimide as the acceptor core,and by changing the structure of the side chain and the substituents on the bay region of the derivative.First,the influence on solubility and optical properties while introduce different the side chains onto the nitrogen atoms of the imide rings were investigated.The results show no clear ascesion on the solubility of the derivatives with increase the number of carbon atoms of the side chain.On the other hand,derivatives with branched alkyl side chain show great improvement on solubility.With a brached alkyl side chain introduced into its structure,this perylene diimide derivative(B2EHPDI)shows different optical properties under different solvents:In tetahydrofuran,the derivative shows no change in the absorption of ultraviolet and visible light.However,due to the intramolecular hydrogen bonds,B2EHPDI shows a great decrease in fluorescence intensity.When choosing chloroform as solvent,same change was not appeared.The reason for this is that the solvation effect of the solvent molecule prevents the formation of intramolecular hydrogen bonds.Then,on the basis of the establishion of the side chain,two kind of compounds with different aromatic ring:naphthalene diimide(B2EHNDI)and benzene diimide(B2EHBDI)were synthesized to compare with B2EHPDI.With the effect of trichloromethane as the solution,the effects of the side chains were masked,and the optical properties of the samples were tested at different concentration gradients.It was found that B2EHPDI had a wide range of absorption in the visible region,mainly in the range of 400-600 nm.And B2EHBDI showed only a weak absorption at 300 nm,without fluorescence.This is due to the small number of π electrons,the nucleus had poor electronic cloud density.The fluorescence intensity of B2EHNDI and B2EHPDI first increased with the increasing concentration and then decreased.When the concentration was 1.0×10-4 mol/L,the fluorescence intensity was the highest.With the concentration continued to increase the fluorescence quenching appeared and fluorescence intensity decreased.A series of D-A-D type derivatives were synthesized with introducing different kinds of donor group onto the bay region of the perylene core of the B2EHPDI which were considered as the acceptor center.When synthesis the dibromo derivative(Br-PDI),the product was found as mixture of isomers through hydrogen nuclear magnetic spectrum,and the mixed ratio was 3:1.The synthesis process was reviewed and excessing the bromine content was helpful to improve the production rate.Using Br-PDI combine with benzene boric acid,4-methoxyl benzene boric acid and 4-formyl benzene boric acid through the Suziki-miyaura coupling reaction,the deribatives P-PDI,M-PDI and F-PDI were synthesized,respectively.The result shows that the derivates all have two main absorption bands at the short and long wavelength range of the ultraviolet-visible light absorption spectrum.And the introducing of the donor group made the short range absorption of the derivatives widen.The F-PDI showed greatly expaned in the short range.The absortion intensity of the M-PDI at long wavelength range decreased and redshift was also significant.Analysising the fluorescence spectrum of the derivatives shows great redshift due to the introduction of the donor group.M-PDI with registration for electronic group show the most obvious redshift.But campare with the raw material,each derivatives show decrease in different ratio.Fluorescence quantum yield data shows that the introduction of the donor group can cause changing on the yield of the derivations.As for F-PDI,camparing with the other two derivatives,it show a good quantum yield which can be considered because of the wide range of absorption at the short wavelength range due to the formyl group.It can be assumed that the energy abrorbed by the formyl group was transfored to the perylene core and was used to generate the fluorescent light.