65625-34-5Relevant academic research and scientific papers
Origin of Spectral Features and Acid-Base Properties of 3,7-Dihydroxyflavone and Its Monofunctional Derivatives in the Ground and Excited States
Serdiuk, Illia E.,Roshal, Alexander D.,B?azejowski, Jerzy
, p. 4325 - 4337 (2016/07/11)
Comprehensive spectral investigations of 3,7-dihydroxyflavone and its two derivatives, which each contain a methyl-blocked hydroxyl group, reveal complex radiation absorption in the 300-450 nm range and emission in the 370-650 nm range. The absorption and fluorescence characteristics of these compounds depend on the pH/H0 of the water/methanol media, which is caused by the existence of the compounds in various protolytic (cationic, neutral, anionic) and tautomeric forms. Combined analysis of steady-state, time-dependent and fluorescence decay spectral data enabled the identification of the emitting species, determination of their lifetimes with respect to radiative and nonradiative deactivation processes, fluorescence quantum yields, protolytic and tautomeric abilities under various conditions, and acidic dissociation constants of the cationic, neutral, and anionic forms of the compounds. Results of calculations carried out at the DFT and TD DFT levels of theory generally confirmed the experimental findings concerning tautomeric/protolytic transformations and equilibria. Computational methods also provided insight into possible tautomerization pathways. Electronically excited molecules are generally much more susceptible to tautomerization and acidic dissociation than ground-state ones. 3,7-Dihydroxyflavone exhibits distinguishable features among the compounds investigated and can be considered as potential spectral indicator of properties (polarity, hydrophobicity, hydrogen-bonding ability) and acidity/basicity of liquid environments.
Single and double intramolecular proton transfers in the electronically excited state of flavone derivatives
Serdiuk,Roshal
, p. 102191 - 102203 (2015/12/11)
In an attempt to create a flavone derivative able to take part in Excited State Intramolecular Double Proton Transfer (ESIDPT), we synthesized two carbonyl derivatives of 3,7-dihydroxyflavone, both containing two different proton-transfer sites as well as related carbonyl derivatives of 3-hydroxyflavone and 7-hydroxyflavone. All the examined hydroxyflavones were found to participate in the Excited State Intramolecular Proton Transfer (ESIPT). ESIPT which involves 3-hydroxyl and 4-carbonyl groups was found to have a higher barrier compared to ESIPT involving 7-hydroxyl and 6/8-carbonyl fragments. According to the data presented, 3,7-dihydroxy-2-phenyl-6-(3-phenylpropanoyl)-4H-chromen-4-one undergoes a two-stage ESIDPT with formation of an intermediate tautomer. This kind of ESIDPT leads to a tautomeric form with an abnormally low rate of radiative deactivation of the excited state, which conditions low fluorescence quantum yield. The behavior of 3,7-dihydroxy-4-oxo-2-phenyl-4H-chromene-8-carbaldehyde in the electronically excited state is similar to 3-hydroxyflavone derivatives, thus we conclude the occurrence of a single ESIPT in this compound.
