Theoretical investigation of electro-luminescent properties in red emission DCM, DCJ, RED and DAD derivatives

During last decade, the DCM derivatives have been used as a laser dye and a red emitter or a red dopant for OLED devices. A series of unsymmetrical DCM, DCJ, and RED as well as symmetrical DAD derivatives of DCM have been recently synthesized and proposed for the commercial applications. It is found experimentally that the optical properties of these materials are determined by their electronic structure. However, no reliable and accurate computational method exists to predict the spectral properties currently. In this paper, we used the semiempirical AM1 and ab initio DFT methods to generate the optimized structures of DCM, DCJ, RED and DAD derivatives. Using the semiempirical ZINDO and ab intio TD-DFT methods, we generated the excitation and emission energies for these derivatives. According to the calculation results, the red shift in the excitation wavelength is in the order RED>DCJ>DCM, the maximum absorption and emission are increasingly red-shifted in DCM derivatives with the electron-donating of the different substituents in the aniline as electron-donating group or with the electron-withdrawing abilities of different substituents in the pyran as electron-withdrawing group.