Construction Of Novel Fluorescent Materials Based On Cyclization Of Fumaronitrile

Over three decades,organic electroluminescent devices(OLEDs),as the core of the third generation in the display technology industry,has had diversified approaches to practical application,and is especially unstoppable in the field of large screen,flexible display,digital painting,Internet of things(electronic shelf labels),and fluorescent sensors.Along with the increasing and fierce competition in the world display industry,it is a prerequisite to master the full-color display technology for the enterprises to occupy the market successfully,since it has already become a crucial standard in measuring the competitiveness of enterprise market.It is crucial for RGB technology,the key to accomplish OLEDs full-color display,to develop high efficiency organic electronic materials.The classical acceptor Diphenyl Fumaronitrile(DPF)has excellent cis-trans isomerism and multiple cyclic paths.On one hand,the double cyano groups can be hydrolyzed and to form a five-membered ring of maleimide through further dehydration when in cis,endowing the materials with hole-transportability.On the other hand,the two cyano groups of DPF could isomerize into a fused-ring structure of phenanthrene by photocyclization,as a kind of new acceptor,providing vast space for new materials.The two types of acceptors share the following three common advantages: firstly,both DPM and DCP,with quite low LUMOs(around-3.30 eV),are suitable for designing red materials;secondly,heteroatoms(oxygen and nitrogen)approach to weak interaction,thus affecting the molecular stacking modes to enhance the fluorescence emission insolid state;in addition,compared with DPF,the rigidness of DPM and DCP increases to different level individually,which not only ensures the luminous intensity and efficiency,but benefits the thermo-stable performance of molecules.In this essay,we took DPM and DCP as the core of the pyramid-skeleton in order,with introducing donors(DPA?TPA?DMAc?PTZ? PXZ and their derivatives)symmetrically in the C(3)and C(4)of the acceptors to build a series of yellow-red emission fluorescence materials.The following studies have been done:First,based on the cyanolysis reaction and photocyclization paths of dicyano-stilbene with excellent cis-trans properties,rigid cores with lower LUMOs-DPM and DCP are obtained.Second,taking DPM and DCP as cores of the pyramid skeleton respectively,and attaching rigid donors PXZ or DMAc symmetrically to C(3)and C(4)of the cores to construct D-A-D structure,deep red molecules presenting fluorescence quenching in liquid,solid as well as crystalline state have been obtained.And based on the optimized structures of the molecules,the mechanism of electron radiative transition has been analyzed to explain reasonsfor their fluorescence quenching.Furthermore,focusing on the reasons for fluorescence quenching of the above-mentioned molecules,a series of adjustments on the electron-pushing ability of donorsand relative rigidness between D-A are carried out,thereby preparing yellow-red emission materials with excellent fluorescence efficiency,good thermal properties,and stable electrochemical performance.First,weakening the steric hindrance of donors,a class of orange-red materials with obvious stimuli-response properties was obtained by attaching DPA or TPA to both sides of the cores,and studying the effect of steric hindrance changes in donor on molecular fluorescence phenomena.Second,reducing the electron-pushing ability and maintaining the rigidity of donors,several materials with dual fluorescent properties were prepared by connecting different sites(2 and 9)of An successively to the cores,to explore the impact of the rigidity of donors on fluorescence quenching of the molecules.In addition,changing the angle between D and A dramatically,several strong orange-red emission materials in solid-state were synthesized through replacingof the C(3)and C(4)positions of acceptors by the 3-position of PXZ or DMAc,to discuss changes in fluorescent properties.Finally,increasing the rigidity of the cores,N-phenyl diphenylmaleimide and phenanthrene maleimide were made up in order to research the effect of the rigid improvement of A or the relative rigid changes between D and A on photo or electroluminescence of materials.