Synthesis, Structures And Propetries Of The Swivel-Cruciform,Molecules Based On5,5-Bibenzothiadiazole

For the extensive material source, and can be simply control the photoelectric properties,morphology by simple chemical means, the organic semiconductor materials have attracted greatattentions of researchers. In electroluminescent light-emitting diodes, organic solid-state laser,organic field effect transistors, organic sensor and other fields, organic semiconductor materialshave been widely researched. Usually, the organic light-emitting materials in organicoptoelectronic devices have high purity, good solubility, good thermal stability and high solidstate luminescence efficiency, etc.In recent years, the swivel-cruciform π-conjugated molecules with excellent photoelectricproperties, have caused a wide range of interest of researchers. The swivel-cruciform structurecan restrain the tendency to form crystal of materials and increase the solubility in commonorganic solvents. By introducing the swivel-cruciform center, we can improve the heat stability,in order to materials can be used in optoelectronic devices.2,1,3-benzothiadiazole is a attractive heterocyclic molecular, usually used to extend theπ-conjugation systems which is among the most important nuclei in the chemistry of luminescentcompounds. It is known that2,1,3-benzothiadiazoles have high electron affinity and areamenable to facile ring modification, simply synthesis. In organic solvent,2,1,3-benzothiadiazole is a very remarkable luminescent center with high luminous efficiency.The compounds containing2,1,3-benzothiadiazole have widespread application inelectroluminescent, even can be used in solar cells. The emission of derivatives are from greenlight of512nm to the deep red light of700nm. But, the liner small molecules containing2,1,3-benzothiadiazole generally afford well-organized crystal structures. The glass transitiontemperature of the derivatives is low. These affected its further application in organicelectroluminescent devices.In this paper we utilize swivel-cruciform type building blocks based on bibenzothiadiazolecore to modify the liner small molecules becoming high luminous efficiency swivel-cruciform molecules with the initial motivation to increase the solubility, to restrain the tendency to formcrystal, to improve the heat stability. We successfully synthesized three swivel-cruciformmolecules based on bibenzothiadiazole tB-dBz、tN-dBz、tPh-dBz and linear small moleculesbased on2,1,3-benzothiadiazole dB-Bz, dN-Bz, dPh-Bz. By several chemical means weconfirm the purity and the structure of the target molecules. Single crystals of dB–Bz, tB–dBzand tPh-dBz were characterized by X-ray diffraction analysis. We found that several moleculeshave the different intermolecular interaction. When the pendant group is benzene ring, the effectof swivel-cruciform bibenzothiadiazole is more obvious. Because of the larger size ofphenanthrene ring, the swivel-cruciform effect of bibenzothiadiazole core decrease.Further，the optical,thermal, electrochemical properties of the compounds are investigated.Through optical properties, We found that the effect of swivel-cruciform is more obvious fortB-dBz to dB-Bz. Solid state luminescence efficiency of tB-dBz is higer7.7%than dB-Bz. Theswivel-cruciform bibenzothiadiazole improve performance, but incompletely restrain thetendency to form crystal of tB-dBz. The effect of the effect of swivel-cruciformbibenzothiadiazole is not obvious for tN-dBz to dN-Bz,tPh-dBz to dPh-Bz. Throughelectrochemical properties, we found that the introducing of swivel-cruciform bibenzothiadiazolelower LUMO energy level. Because of the different size of the the pendant group, electron clouddistribution of swivel-cruciform molecules appears a different degree of charge separationphenomenon. Through thermal properties, we found that the heat stability of severalswivel-cruciform molecules is higher than the liner small molecules. For the compouds dB-Bzand tB-dBz, we also found the swivel-cruciform bibenzothiadiazole incompletely restrain thetendency to form crystal of tB-dBz. For the others the swivel-cruciform molecules appearamorphous. The specific application of compounds remains to be further explored. Our workhas broaden the scope of building the swivel-cruciform center in photoelectric functionalmaterials, increased the experience of building materials based on the swivel-cruciform center.