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Excited state properties, fluorescence energies, and lifetime of a poly(fluorene‐pyridine) copolymer, based on TD‐DFT investigation
Author(s) -
Chidthong Rungtiwa,
Hangbua Supa,
Aquino Adelia J. A.,
Wolschann Peter,
Lischka Hans
Publication year - 2007
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.20685
Subject(s) - fluorene , copolymer , excited state , pyridine , fluorescence , photochemistry , chemistry , computational chemistry , materials science , polymer , atomic physics , organic chemistry , physics , quantum mechanics
The structural and electronic properties of the fluorene‐pyridine copolymer (FPy) n , ( n = 1–4) were investigated theoretically by means of quantum mechanical calculations based on density functional theory (DFT) and time‐dependent DFT (TD‐DFT) using the B3LYP functional. Geometry optimizations of these oligomers were performed for the ground state and the lowest excited state. It was found that (FPy) n is nonplanar in its ground state, whereas a more pronounced trend toward planarity is observed in the S 1 state. Absorption and fluorescence energies have been extrapolated to infinite chain length making use of their good linearity with respect to 1/ n . An extrapolated value of 2.64 eV is obtained for vertical excitation energy. The S 1 ←S 0 electronic excitation is characterized as a highest occupied molecular orbital to lowest unoccupied molecular orbital transition and is dominating in terms of oscillator strength. Fluorescence energies and radiative lifetime were calculated as well. The obtained results indicate that the fluorescence energy and radiative lifetime of (FPy) n are 2.16 eV and 0.38 ns, respectively. The decrease of fluorescence energy and radiative lifetime with the increase in the chain length is discussed. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007