Aesculetin Exhibits Strong Fluorescent Photoacid Character.

Coumarins are bioactive molecules that often serve as defenses in plant and animal systems, and understanding their fundamental behavior is essential for understanding their bioactivity. Aesculetin (6,7-dihydroxycoumarin) has recently attracted attention due to its ability to act as an antioxidant, but little is known about its photophysical properties. The fluorescence lifetimes of its neutral and anion form in water are 19 ± 2 ps and 2.

Cryogenic Infrared Action Spectroscopy Fingerprints the Hydrogen Bonding Network in Gas-Phase Coumarin Cations.

We report cryogenic vibrational spectra of gas-phase cations of two common hydroxycoumarins, scopoletin and esculetin, as well as their glycosidic derivatives, scopolin and esculin. The study allows direct observation of the intramolecular interactions between the hydroxyl groups of these molecules. We use cryogenic messenger-tagging IR action spectroscopy to detect vibrational bands in the 3100-3800 cm spectral range and discuss the corresponding structural characteristics and hydrogen bonding networks that they imply.

Fluorescence of Scopoletin Including its Photoacidity and Large Stokes Shift.

Scopoletin is highly fluorescent in water and acts as a photoacid exhibiting excited-state proton transfer, ESPT, competitive with fluorescence. Its absorbance and emission spectral characteristics yield ground-state and excited-state pK values of 7.4 ± 0.

Photochemistry of UV-excited trifluoroacetylacetone and hexafluoroacetylacetone I: infrared spectra of fluorinated methylfuranones formed by HF photoelimination.

The photochemistry of gas-phase 1,1,1-trifluoroacetylacetone (TFAA) excited with ultraviolet (UV) light involves a significant photoelimination channel that produces hydrogen fluoride and a fluorinated methylfuranone, 2,2-difluoro-5-methyl-3(2H)-furanone (2FMF). This pathway is remarkable because it is a gas-phase unimolecular reaction that forms a five-membered ring product. This report is the first of such a TFAA photoelimination channel, which is similar to one observed with 1,1,1,5,5,5-hexafluoroacetylacetone (HFAA), resulting in 2,2-difluoro-5-trifluoromethyl-3(2H)-furanone.

Competition between photochemistry and energy transfer in UV-excited diazabenzenes. 4. UV photodissociation of 2,3-, 2,5-, and 2,6-dimethylpyrazine.

The quantum yield for HCN formation via 248 nm photodissociation of 2,3-, 2,5-, and 2,6-dimethylpyrazine (DMP, C6N2H8) was measured using diode laser probing of the HCN photoproduct. The total quantum yield is phi = 0.039 +/- 0.