Excited state proton transfer in 3,6-bis(4,5-dihydroxyoxazo-2-yl)benzene-1,2-diol

Single and double intramolecular proton transfers in the electronically excited state of flavone derivatives

“…For synthesis of 2a (Scheme 2), 3-hydroxy-7-benzyloxyavone (10) was chosen as a precursor, synthesized from commercially available 1-(2,4-dihydroxyphenyl)ethanone (7), according to the procedure described earlier: 15 7 was treated with benzyl chloride, leading to 8a, then converted to chalcone derivative 9a with benzaldehyde in basic NMP, which was then oxidatively cyclized in basic MeOH in the presence of H 2 O 2 (Algar-Flynn-Oyamada reaction). 10 was subsequently alkylated with dimethylsulfate, followed by cleavage of benzyl group in HBr solution in acetic acid to yield 12.…”

“…Hypothetically, ESIDPT can be as useful as ESIPT or even more, if one expects higher energy losses of the electronically excited molecule before it emits light. Various bifunctional organic compounds were designed and synthesized, including derivatives of salicylic acid, 4 oxazoles, [5][6][7] and chromones, [8][9][10][11] and subsequently investigated from the point of view of ESIDPT by steady-state and time-dependent absorption and uorescent spectroscopies, as well as ab initio and semiempirical computational techniques. Generally, it was found that aer excitation these compounds undergo single ESIPT, while occurrence of ESIDPT is much less favorable.…”

Fluorescence emissions of imide compounds and end-capped polyimides enhanced by intramolecular double hydrogen bonds

“…Furthermore, the excited-state intramolecular double proton transfer (ESIDPT) process, in which two protons separately involved in intra-HB are transferred by photo-irradiation, has also attracted interest due to its importance in chemistry and biology. [21][22][23] Among low-Mw compounds inspiring ESIDPT, the question of whether the two-proton transfer processes take place concertedly, or stepwise, has been discussed. For instance, Glasbeek et al [24][25][26][27][28] have performed extensive studies regarding the ESIDPT mechanism in [2,2 0 -bipyridyl]-3,3 0 -diol (BP(OH) 2 ) using a fluorescence up-conversion technique and confirmed that BP(OH) 2 exerts a bifurcated type of ESIDPT that produces both a single-proton-transferred form (mono-keto form) and a double-proton-transferred form (di-keto form) nearly simultaneously (within a duration of B100 fs).…”

Fluorophores for Excited‐State Intramolecular Proton Transfer by an Yttrium Triflate Catalyzed Reaction of Isocyanides with Thiocarboxylic Acids

“…[1,2] ESIPT process has attracted multidisciplinary attention due to its fundamental importance in chemistry,i n biology,a nd in developing novel functional molecules. Bis-flavonols, [4] bis-2-(2'-hydroxyphenyl)benzazole [5] and 2,2'bipyridyl-3,3'-diol [6] are prominent examples,t he proton transfer mechanisms of which have been examined in detail by computation. From the viewpoint of molecular design, two classes of ESIDPT could be considered:a )T wo proton transfer processes occur independently (type A,Scheme 1a).…”