Study of the fluorescent properties of salicylic acid derivatives in solutions

Photolysis of sulfosalicylic acid in aqueous solutions over a wide pH range

“…Indeed, if the absorption band of phenol in aqueous solutions is centered at 270 nm (ε = 1.5 × 10 3 M −1 cm −1 ), SA has a fairly strong absorption band at 300 nm (λ max = 303 nm, ε = 3.5 × 10 3 M −1 cm −1 ) [23]. The absorption band of SA shifts to the red upon substitution [16].…”

“…1B). This accounts for the large Stokes shift of SA fluorescence and its derivatives (λ em ≈ 440 nm [11][12][13]16]). Rotamer B cannot undergo ESIPT and has fluorescence band with maximum at 330 nm.…”

“…This is accompanied by an increase of lifetime (from 1 to 6-8 ns) and fluorescence quantum yield [16][17][18][19]. This is due to proton transfer to the solvent in the ground state, which results in the formation of the anion of the corresponding acid whose photophysical properties differ from those of the neutral.…”

“…In polar solvents, the formation of the proton-transferred instead of the tautomeric form of SA upon excitation is energetically favored by solvation. According to theoretical calculations on the SA anion, the activation energy for the intramolecular proton transfer from the hydroxyl to the carboxyl group, which can account for the increase of the fluorescence quantum yield of SA in polar solvents [16], amounts to 4 kJ/mol only [14].…”

Crystallization-induced light-emission enhancement of diphenylmethane derivatives

“…The large Stroke shifts are indicative of intramolecular charge transfer in the excited state, which for compounds 1e6, could be explained by the tautomerisation-transfer of the labile proton from the hydroxyl to the carbonyl group. 13,14 The luminescence of the different compounds in THF ranges from almost non-emissive (2 and 3) and weakly luminescent (diesters 4e6, ff¼0.02e0.03) to a maximum quantum yield of ca. 0.10 (diacid 1).…”