Design,Synthesis And Properties Of Anthracene-based Organic Conjugated Materials

The extended?-electron delocalization structure bring many novel optoelectronic properties to organic conjugated materials that has attracted a lot of attention.The energy band of the material can be controlled by molecular design,thus organic conjugated materials are applied to the preparation of organic electronic devices,detection and biological imaging,etc.It has been greatly developed from the basic research of the laboratory to the practical application of industry and life.As a polycyclic aromatic hydrocarbon consisting of three benzene rings,anthracene has attracted much attention due to its high charge transfer ability and excellent luminescent properties.How to use the structure of anthracene to obtain optoelectronic materials with excellent properties is a problem worthy of study.In this paper,a series of new organic conjugated materials have been prepared by using anthracene and its derivatives as the core.The luminescent properties under different conditions were studied.The effects of molecular structure and aggregation state on conjugation degree and luminescence properties of the products were investigated.First,we designed two conjugated molecules,FAF and FAAF,with anthracene and9,9'-bianthracene as the core,and compared their luminescence properties and discussed the influence of molecular structure on luminescence of products by theoretical calculation.In the solution state,FAF is blue luminescence??=440 nm?,while the luminescence of FAAF is affected by the solvent,indicating that the introduction of the bianthracene group leads to the change of the molecular conformation under different solvents and the change of degree of conjugation,therefore,changing the wavelength of the luminescence.In the solid state,the emission wavelengths of FAF and FAAF are both around 450 nm.It is known from theoretical calculation that the dihedral angle of the molecule between fluorene unit and anthracene unit are about 90°,which leads to low conjugation degree and large steric hindrance,and prevents the stacking of molecules,thus showing the same blue luminescence.Both products have a CIE coordinate y<0.10,which has the potential to be used as a blue emitting OLED material.Secondly,in order to investigate the effect of anthracene unit content on the luminescent properties of polymers,a series of conjugated polymers PFA,PFAA,PF₂A₁AA₁ and PF₃A₁AA₂ with anthracene chains were prepared by Suzuki polymerization that anthracene and bianthracene as the main monomers are copolymerized with dihexyl fluorene.It was found that the red shift of fluorescence emission of polymers in solution was caused by the increase of the content of bianthracene segments in the main chain of polymers,and the fluorescence wavelength was also affected by different solvents.This may result in different conformations due to the different interaction of the polymer with different solvents,causing a change in the degree of conjugation of the polymer.In the state of solid powder,the polymer has different degrees of cyan-green emission,in which PF₂A₁AA₁ and PF₃A₁AA₂ powders with both anthracene and bianthracene chain links are green luminescence,indicating that the change of polymer aggregation state also affects luminescence.Finally,a series of fluorene-anthracene copolymers?PFA?and fluorene-naphthalene copolymers?PFN?were prepared by solid-state oxidative coupling polymerization using FeCl₃ as oxidation catalyst.It was found that the copolymer has a random structure consisting of 2,7-linked fluorene units and 9,10-anthracene units or 1,4-naphthalene units.The XRD spectra show that the increase of fluorene units in the main chain of the copolymer will lead to the increase of its crystallinity.These products exhibit good thermal stability and high char residue rates.The optical properties of the products can be adjusted by using different ratios of fluorene to anthracene or naphthalene.PFA shows red luminescence in solid state and red shift of emission wavelength with increasing concentration in solution state which luminescence changes from blue to red.As a reference,PFN also shows the same trend of luminescence change.This is attributed to the change of effective conjugate length of a single polymer and the formation of polymer aggregates and stimulated excimers.These unique properties give PFA and PFN potential applications in the field of optoelectronics.The polymer has obvious detection ability for THF,and it is expected to be used as a fluorescent probe for THF detection.