Photophysics of Anthril in Fluids and Glassy Matrixes

Abstract

Photophysics of 9,9'-anthril have been investigated at room temperature and cryogen phase (77 K) exploiting steady state and time-resolved emission techniques together with quantum chemical calculations. Absorption spectra, emission spectra, and emission lifetimes of anthril have been recorded and analyzed in polar ethanol and nonpolar methylcyclohexane media. Both room temperature and cryogenic experiments reveal a single emission band upon excitation at the nπ* absorption band whereas on exciting the system at the ππ* band, dual emission bands have been observed. Characterization of these two fluorescence bands to be originating from near-trans and relaxed skew conformers have been made by monitoring their differential effect on varying the polarity of solvents. Similarly, two phosphorescence bands have been assigned to trans and cis geometries by looking at the change in the emission spectra in the two rigid matrixes of different polarity. Observation of a single isoemissive point in the time-resolved area normalized emission spectroscopy (TRANES) for both fluorescence and phosphorescence emissions unambiguously validates the coexistence of the two conformers in the excited singlet and triplet states, respectively. Qualitative quantum chemical calculations indicate that the S and T states are responsible for the dual fluorescence and phosphorescence bands. Effortless transitions from the higher excited singlet states (S or S) to the lowest energy excited singlet (S) state because of their energy proximity discard any possibility of S emission, consistent with two other 1,2-dicarbonyl compounds like α-furil and 2,2'-pyridil, while going in contrast to the observation of S emissions from benzil and α-naphthil. On the basis of the vivid photophysical studies on five probes in fluid media and 77 K glassy matrixes, we conclude that exhibition of the S emission for aromatic 1,2-dicarbonyl compounds is truly system dependent and not a general phenomenon for all the molecular systems in the series.

Excited-State Dynamics of Room-Temperature Phosphorescent Organic Materials Based on Monobenzil and Bisbenzil Frameworks

“…Similar to the heavy-metal effect, the incorporation of carbonyl groups in organic molecules tends to induce greater SOC by lowering the S 1 -T 1 energy gap according to the orbital selection rule between the initial and final state upon photoexcitation—that is, the El-Sayed rules [ 18 , 19 ]. Benzil, benzil derivatives, and dicarbonyl compounds ( Figure 1 ) have been reported to emit either RTP or phosphorescence at liquid nitrogen temperatures [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]. Among these compounds, benzil has been the subject of extensive investigations in the field of photochemistry because conformational changes upon photoexcitation have been reported [ 18 , 24 , 25 , 27 , 28 , 29 ].…”

Arsenate and arsenite adsorption in relation with chemical properties of alluvial and loess soils

“…Studies was conducted on As(V) and As(III) adsorption by amorphous iron and aluminum oxides, as well as on clay minerals, i.e., kaolinite and montmorillonite. 16 For the modeling of As(V) and As(III) adsorption the most widely used analytical isotherms are the Langmuir isotherm 17 and the Freundlich isotherm. 18 The studies on the arsenic adsorption in relation with lithology and development are scarce.…”