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Structural, electronic, and optical properties of oligoquinolines for light‐emitting diodes
Author(s) -
Li LeiJiao,
Feng JiKang,
Ren AiMin
Publication year - 2009
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.1434
Subject(s) - chemistry , density functional theory , excited state , singlet state , ab initio , ground state , ionization energy , emission spectrum , basis set , absorption spectroscopy , quinoline , time dependent density functional theory , ab initio quantum chemistry methods , electronic structure , ionization , spectral line , computational chemistry , molecule , atomic physics , organic chemistry , ion , physics , quantum mechanics , astronomy
The purpose of this work is to provide an in‐depth investigation of the electronic and optical properties of a series of n ‐type conjugated oligomers, including 4‐phenyl‐6‐(4‐phenylquinolin‐6‐yl)quinoline (B1), 6,6′‐bis(2,4‐diphenylquinoline) (B1PPQ), 6,6′‐bis(2‐(4‐ tert ‐butylphenyl)‐4‐phenylquinoline) (BtBPQ), 6,6′‐bis(2‐ p ‐biphenyl)‐4‐phenylquinoline) (B2PPQ), and 4‐(6‐(2‐(4‐aminophenyl)‐4‐phenylquinolin‐6‐yl)‐4‐phenylquinolin‐2‐yl)benzenamine (BNPPQ). The geometric and electronic structures of the oligomers in the ground state were investigated using density functional theory (DFT) and the ab initio HF, whereas the lowest singlet excited states were optimized with ab initio CIS. To assign the absorption and emission peaks observed in the experiment, we computed the energies of the lowest singlet excited states with time‐dependent (TD) DFT (TD‐DFT). All DFT calculations were performed using the B3LYP functional and the 6‐31G basis set. The results show that the HOMOs, LUMOs, energies gaps, ionization potentials and electron affinities for each molecular are significantly affected by varying the aryl substituents, which favor the hole injection into OLEDs. The absorption and emission spectra exhibit red shifts to some extent [the absorption spectra: 335.85 (B1)< 370.63 (B1PPQ) < 376.77 (BtBPQ)< 388.67 (B2PPQ)< 412.93 nm (BNPPQ); the emission spectra: 391.48 (B1)< 430.11 (B1PPQ)< 435.86 (BtBPQ)< 444.57 (B2PPQ)< 463.28nm (BNPPQ)]. The radiative lifetimes ( τ ) of each oligomers are calculated as well. Because of introducing the cooperation with the electron donators such as the amidocyanogen in the common 4‐phenyl‐6‐(4‐phenylquinolin‐6‐yl)quinoline core for BNPPQ, which results in improving the hole‐creating ability. Copyright © 2008 John Wiley & Sons, Ltd.