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Synthesis, optical properties and ultrafast dynamics of aza-boron-dipyrromethene compounds containing methoxy and hydroxy groups and two-photon absorption cross-section

[Display omitted] ► Linear and nonlinear optical absorptions of aza-BODIPY were investigated. ► New bands phenolate form of hydroxyl appeared depending on basicity of solution. ► This leads to fluorescence quenching. ► Lifetime of the charge-separated state is on the order of ultrafast time scales....

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Published in:Journal of photochemistry and photobiology. A, Chemistry. Chemistry., 2012-11, Vol.247, p.24-29
Main Authors: Küçüköz, Betül, Hayvalı, Mustafa, Yılmaz, Halil, Uğuz, Birhan, Kürüm, Ulaş, Yaglioglu, H. Gul, Elmali, Ayhan
Format: Article
Language:English
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Summary:[Display omitted] ► Linear and nonlinear optical absorptions of aza-BODIPY were investigated. ► New bands phenolate form of hydroxyl appeared depending on basicity of solution. ► This leads to fluorescence quenching. ► Lifetime of the charge-separated state is on the order of ultrafast time scales. ► Aza-BODIPY compounds showed TPA in wide spectral range (1200–1450nm). In this work, aza-boron-dipyrromethene (aza-BODIPY) compounds containing methoxy and hydroxy groups were synthesized. The effects of substitution and intramolecular charge transfer on linear and nonlinear optical absorptions (especially two photon absorption) of these BODIPY derivatives were investigated. Drastic spectral changes of aza-BODIPY compounds containing hydroxy group were observed in linear absorption spectra depending on basicity of solution. New bands in linear absorption spectra of phenolate form of these compounds appeared bellow 500nm and above 700nm in THF solution. These findings were caused by occurrence of the intramolecular charge transfer state in the phenolate form. Ultrafast pump probe spectroscopy experiments revealed that phenolic form shows only bleaching signal around 600nm. On the other hand, the phenolate form showed fast growing nonlinear absorption signals bellow 500nm and above 700nm regions in addition to the bleaching signal around 600nm. Intramolecular charge transfer state occurs above 700nm and the lifetime of this state is found on the order of ultrafast time scales. Since the excitation of the fluorescence experiments is at 600nm there is no fluorescence signal due to the relaxation of the energy through intramolecular charge transfer state. Aza-BODIPY compounds containing methoxy group did not show any two photon absorption properties due to weak electron-donating strength of methoxy group while aza-BODIPY compounds containing hydroxyl showed two photon absorption properties in wide spectral range (1200–1450nm). Our results also indicated that intramolecular charge transfer enhances two photon absorption properties.
ISSN:1010-6030
1873-2666
DOI:10.1016/j.jphotochem.2012.08.003