Acta Phys. -Chim. Sin. ›› 2010, Vol. 26 ›› Issue (04): 1075-1081.

• QUANTUM CHEMISTRY AND COMPUTATION CHEMISTRY •

Photoelectric Properties of 9,9’-Spirobifluorene

ZHANG Cheng, YAN Yan, CHEN Li-Tao, MA Chun-An

1. State Key Laboratory Breeding Base of Green Chemistry-Synthesis Technology, College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014, P. R. China
• Received:2009-08-12 Revised:2009-11-13 Published:2010-04-02
• Contact: CHEN Li-Tao E-mail:ltchen@zjut.edu.cn

Abstract:

9,9'-Spirobifluorene oligomers ((SBF)n(n=1-4)) were fully optimized using density functional theory (DFT) at the B3LYP/6-31G(d) level. We obtained the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) energies, and HOMO-LUMO energy gap from these DFT calculations. All molecules have good π conjugation structures. Fromthe optimized geometries of the cationic and anionic charged states, we calculated the ionization potential (IP), electron affinity (EA), hole extraction potential (HEP), electron extraction potential (EEP), and the reorganization energy. The singlet excited geometry of 9,9'-spirobifluorene was calculated using the single-excitation configuration interaction (CIS)/3-21G method. Absorption and emission spectra were obtained by employing time-dependent (TD)-DFTcalculations. Results showthat as the lengths of oligomers increase, the HOMO-LUMOenergy gaps become narrower, the hole injection and the electron transport properties improve, the lowest excitation energies decrease, the oscillator strength (f) increases, and the maximum absorption wavelengths (λmax) show a red shift. The electronic and electrochemical properties of the polymer were predicted by extrapolating the properties of the oligomers with an infinite reciprocal chain length. To investigate the influence of substituting the 9 position of the fluorene, some parameters of the parent fluorene ((FL)n(n=1-4)) were calculated for comparison. Fromthis comparison, it is obvious that spiro-functionalization at the fluorene C-9 bridge position can greatly improve the electron and hole transport properties and the excellent emission spectral quality of the fluorene is maintained.

MSC2000:

• O641