Design And Synthesis Of Phenanthro[9,10-d]-imidazole As Photoelectric Functional Materials

Organic optoelectronic materials has made great progress in the design of newmaterials and device fabrication. Red and green emitters with excellent comprehensiveproperties have been well developed. The contradiction between wide band gap andbalanced charge injection and transport in blue materials is obstacles to their development.Phenanthro[9,10-d]imidazole (PI), as a new block for blue fluorescent materials, exhibitslower electron and hole injection barrier, excellent thermal stability, facial syntheticprocess and modification flexibility. In this paper,1,2-diphenyl-1H-phenanthro[9,10-d]-imidazole (PPI) was chosen as a model compound for PI-based compound. By tuning thesubstituent structure and linked mode in1,2-position of the imidazole ring, someregularities are revealed. Some results was shown as follows:Fluorescent center mainly located on imidazole ring in phenanthroimidazole unit, sothe substituent structure attaching imidazole ring plays a more important role inluminescence property. Because of participating the formation of the frontier molecularorbitals, the C2-position affect the emitting light color of compounds. While theN1-position exhibits less influence, it is not be ignored.For discussion of this relationship, a series of phenanthroimidazole derivatives wereprepared by tuning the substituted group in phenyl attached N1or C2position. Comparingwith the split fluorescence spectra in single molecular of PPI and its derivatives,R4-substituted position in phenyl attached N1and C2played more important role insubstituent effect than others. When the stronger electron-withdrawing group was inserted,the proportion of low-energy level emission increase in split fluorescence spectra and thespectra red-shift. On the basis of the conclusion, the molecule ONBPPI show excellentperformance and the result consistent with the above conclusions.CN-BPPI is obtained from cyano-group inserted at the phenyl of N1position inimidazole ring, and exhibited unchanged blue emission and balance the charge injectionand transport as expected as BPPI. And L-BPPI and Z-BPPI easily prepared through tuning biphenyl structure of C2position and exhibit excellent thermal stability, emitting lightcolor towards deep-blue fluorescence emission.The results imply that the PI unit is an excellent building block for blue emission. ThePI monomers are prepared by optimizing experimental condition, and the polymerSXH-P1was coupled with the boronation PI (M4) unit and the halogenation one (M6). Itexhibits excellent photoelectric properties as previous report, and the electroluminescenceof the device based on SXH-P1locates in the deep blue region with a CIE (0.158,0.078).