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Excited state properties, fluorescence energies, and lifetimes of a poly(fluorene‐phenylene), based on TD‐DFT investigation
Author(s) -
Chidthong Rungtiwa,
Hangbua Supa
Publication year - 2010
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.21429
Subject(s) - density functional theory , excited state , oscillator strength , homo/lumo , ground state , atomic physics , singlet state , fluorene , fluorescence , time dependent density functional theory , planarity testing , excitation , materials science , molecular orbital , electronic structure , chemistry , molecular physics , computational chemistry , molecule , crystallography , physics , polymer , optics , spectral line , quantum mechanics , astronomy , organic chemistry , composite material
The structural and electronic properties of fluorene‐phenylene copolymer (FP) n , n = 1–4 were studied by means of quantum chemical calculations based on density functional theory (DFT) and time dependent density functional theory (TD‐DFT) using B3LYP functional. Geometry optimizations of these oligomers were performed for the ground state and the lowest singlet excited state. It was found that (FP) n is nonplanar in its ground state while the electronic excitations lead to planarity in its S 1 state. Absorption and fluorescence energies were calculated using TD‐B3LYP/SVP and TD‐B3LYP/SVP+ methods. Vertical excitation energies and fluorescence energies were obtained by extrapolating these values to infinite chain length, resulting in extrapolated values for vertical excitation energy of 2.89 and 2.87 eV, respectively. The S 1 ← S 0 electronic excitation is characterized as a highest occupied molecular orbital to lowest unoccupied molecular orbital transition and is distinguishing in terms of oscillator strength. Fluorescence energies of (FP) n calculated from TD‐B3LYP/SVP and TD‐B3LYP/SVP+ methods are 2.27 and 2.26 eV, respectively. Radiative lifetimes are predicted to be 0.55 and 0.51 ns for TD‐B3LYP/SVP and TD‐B3LYP/SVP+ calculations, respectively. These fundamental information are valuable data in designing and making of promising materials for LED materials. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010