Description of solvent effect on the visible absorption spectrum of fluorenone radical anion

Wagner-Czauderna, Elżbieta; Lipka, Robert; Kalinowski, Marek K.

doi:10.1002/bbpc.19971010404

Cited by 7 publications

(7 citation statements)

References 26 publications

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“…This confirms the presence of deactivation modes other than fluorescence and intersystem crossing. While fluorenone is known to readily undergo photoreduction to form a radical anion, , the presence of this intermediate can be precluded in part owing to the absence of a visible radical anion in the transient absorbance measurements. Moreover, the formation of radical ions would eventually lead to product degradation with prolonged irradiation.…”

Section: Resultsmentioning

confidence: 99%

Oligofluorenes as Polymeric Model Compounds for Providing Insight into the Triplets of Ketone and Ketylimine Derivatives

2012

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A series of oligofluorenes ranging between one and three repeating units were prepared as structurally well-defined representative models of polyfluorenes. The photophysics of the oligofluorene models were investigated both by laser flash photolysis and steady-state fluorescence. The effects of the ketone and ketylimine functional groups in the 9-position on the photophysical properties, notably the triplet quantum yield (Φ(TT)) by intersystem crossing and the absolute fluorescence quantum yields (Φ(fl)), were investigated. The singlet depletion method was used to determine both the Φ(TT) and molar absorption coefficients of the observed triplets (ε(TT)). Meanwhile, the absolute Φ(fl) were determined using an integrating sphere. It was found that both the ketone and ketylimine substituents and the degree of oligomerization contributed to quenching the oligofluorene fluorescence. For example, the Φ(fl) was quenched 5-fold with the ketylimine and ketone substituents for the bifluorenyl derivatives compared to their corresponding 9,9-dihexyl bifluorenyl counterparts. Meanwhile, the Φ(fl) quenching increased 14 times with the trifluorenyl ketone and ketylimine derivatives. Measured Φ(TT) values ranged between 22 and 43% for the difluorenyl derivatives with ε(TT) on the order of 13 000 cm(-1) M(-1). The Φ(TT) decreased to <10% concomitant with doubling of the ε(TT) when the degree of oligomerization was increased to 3. A new fluorescence emission at 545 nm formed at low temperatures for the ketone and ketylimine oligofluorene derivatives. The emission intensity was dependent on the temperature, and it disappeared at room temperature.

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Section: Resultsmentioning

confidence: 99%

Oligofluorenes as Polymeric Model Compounds for Providing Insight into the Triplets of Ketone and Ketylimine Derivatives

2012

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“…DMF was purchased as Fluka certified solvent for UV spectroscopy and used without purification. TEAP from Merck was purified by recrystallization from triply distilled water and vacuum-dried at 50ЊC; its concentration in solutions was 0.1 M. A spectroelectrochemical cell and apparatus, as well as the procedures and conditions of the experiments, were the same as those used previously in this laboratory (14).…”

Section: Methodsmentioning

confidence: 99%

Visible Absorption Spectra of Diaryl Carbonyl Radical Anions

Wagner-Czauderna

Filipek

Lipka

et al. 1997

Microchemical Journal

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“…The magnitudes of blue shifts for Bp – are larger than those for Fl – in the case of the gas-phase anions solvated with a single polar molecule, whether it is aprotic or protic . This trend holds for the fully solvated anions in solutions or matrices of aprotic solvents. − Yet, it was reported that blue shifts of Fl – in protic solvents are much larger than those of Bp – . ,,− Figure shows a graph of photoabsorption peak shifts relative to those in the gas phase for Fl – and Bp – , with respect to E T (30) of several solvents, which is one of the most accepted solvent polarity parameters. , …”

Section: Introductionmentioning

confidence: 95%

“…Solvent effects on electronic structures of molecules often result in shifts of optical transition energies, − which have been widely investigated to be correlated with the chemical reactivity in condensed phases. − Electronic spectra of aromatic ketyl anions (i.e., radical anions of aromatic carbonyl compounds) have fascinated many researchers for a long time, because significant solvatochromic shifts are observed for the intramolecular charge-transfer (ICT) absorption band, − where most population of the excess electron moves from the carbonyl (CO) group to the aromatic rings. Larger solvation energy in the electronic ground state relative to the excited state causes a blue shift of the absorption peak.…”

Section: Introductionmentioning

confidence: 99%

“…Photoabsorption peak-energy shifts in the condensed phases for Bp – (red squares) and Fl – (blue squares) relative to those in the gas phase, plotted against E T (30) values (ref ) of solvents, (a) 2-methyltetrahydrofuran, (b) sec -butylamine, (c) N , N -dimethylformamide, (d) acetonitrile, (e) 1-propanol, (f) ethanol, and (g) water. The shifts are derived from the peak energies in refs − and . Note that the difference of the shifts between Bp – and Fl – is more remarkable in the protic solvents (see text).…”

Section: Introductionmentioning

confidence: 99%

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Photodetachment Spectroscopy of Fluorenone Radical Anions Microsolvated with Methanol: Rationalizing the Anomalous Solvatochromic Behavior Due to Hydrogen Bonding

et al. 2015

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The attribution of the extraordinary blue shift for the intramolecular charge-transfer absorption band of fluorenone radical anion solvated in protic media was investigated by means of photodetachment spectroscopy of the gas-phase anions microsolvated with methanol, in conjunction with quantum chemical calculations based on density functional theory. Sequential shifts of the vertical detachment energy as a function of the cluster size are consistent with theoretical predictions, where up to two methanol molecules can directly attach to the carbonyl group. In the photodetachment excitation spectra as alternatives to the photoabsorption spectra, with increasing cluster size, a new absorption band grows in the higher-energy region, which coincides with the blue-shifted band in protic media. Spectral simulations using time-dependent density functional theory with the CAM-B3LYP functional reproduced the feature of the phenomenon. Analyses on the electronic configuration elucidated that the extraordinarily blue shifts originate from energy-level repulsion due to solvation-induced resonant coupling with another electronic state. The orbital transition for the counterpart state corresponds to the first absorption band of the neutral fluorenone molecule, which has small oscillator strength from the ground state. It was found that correction of long-range electron exchange correlation is important for the spectral simulation involving the electronic-state coupling.

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Description of solvent effect on the visible absorption spectrum of fluorenone radical anion

Cited by 7 publications

References 26 publications

Oligofluorenes as Polymeric Model Compounds for Providing Insight into the Triplets of Ketone and Ketylimine Derivatives

Oligofluorenes as Polymeric Model Compounds for Providing Insight into the Triplets of Ketone and Ketylimine Derivatives

Visible Absorption Spectra of Diaryl Carbonyl Radical Anions

Photodetachment Spectroscopy of Fluorenone Radical Anions Microsolvated with Methanol: Rationalizing the Anomalous Solvatochromic Behavior Due to Hydrogen Bonding

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