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Photophysical properties of the asymmetrically substituted spirobifluorenes spiro‐DPO and spiro‐MeO‐DPO
Author(s) -
Brendel Cornelia M.,
Dias Fernando B.,
Saragi Tobat P. I.,
Monkman Andy P.,
Salbeck Josef
Publication year - 2009
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.200925302
Subject(s) - phosphorescence , excited state , chemistry , fluorescence , luminescence , dipole , photochemistry , ground state , singlet state , absorption (acoustics) , population , transition dipole moment , triplet state , atomic physics , materials science , physics , organic chemistry , optoelectronics , quantum mechanics , sociology , composite material , demography
The photophysical behaviour of the oxadiazolyl (PBD) and diphenylamino (TAD) substituted spirobifluorenes 2′,7′‐bis‐( N , N ‐diphenylamino)‐2‐(5‐(4‐ tert ‐butylphenyl)‐1,3,4‐oxadiazol‐2‐yl)‐9,9′‐spirobifluoren (spiro‐DPO) and 2′,7′‐bis‐( N , N ‐diphenylamino)‐2‐(5‐(4‐ tert ‐butylphenyl)‐1,3,4‐oxadiazol‐2‐yl)‐9,9′‐spirobifluoren (spiro‐MeO‐DPO) has been investigated by temperature‐dependent steady‐state absorption and luminescence spectroscopy and gated measurements. Fluorescence and phosphorescence lifetime measurements, relative quantum yields and dipole moments of the excited states have been determined. Asymmetrically substituted spirobifluorenes exhibit charge‐transfer (CT) emission due to coupling (spiroconjugation) between the fluorene fragments of spirobifluorene. They show a considerable ground‐state dipole moment and exist as equilibrating conformeres. Population of the CT state only occurs after absorption to the locally excited singlet state. The CT fluorescence is dominated by the emission of two equilibrating conformeres with similar dipole moments. At low temperature they planarize in both molecular halves and show strong phosphorescence that is still detectable at room temperature.