Radiationless deactivation of the excited phototautomer form and molecular structure of ESIPT-compounds

Abstract

Correlation between the character of electronic density redistribution in the excited normal and phototautomer forms, which are involved in the excited state intramolecular proton transfer (ESIPT) reaction, and the rates of primary photoprocesses--proton phototransfer and radiationless deactivation of the phototautomer form--was analysed on the qualitative level. It was revealed that noticeable improvement of fluorescence properties of ESIPT molecules could be achieved by directed modification of their chemical structure, most importantly by the introduction of electron withdrawing substituents into their proton donor moieties. Several facts are presented in favour of the last statement.

2-(benzimidazol-2-yl)-3-hydroxychromone derivatives: spectroscopic properties and a possibile alternative intramolecular proton phototransfer

“…This decreases the yield of the ESIPT reaction product (T*), which is observed in the rise of the intensity of the N* emission (see Figure 4). Another possible mechanism for the change in IFN*/I F T* is the pronounced quenching of the phototautomer fluorescence in polar media [18]. Both mechanisms result in an increase of the ratio; determination of their relative contributions requires special investigation.…”

A Set of Fluorescent Probes to Study the Influence of Low Molecular Weight Cryoprotectants on Human Erythrocyte Membranes

“…In the excited state the ortho-hydroxy derivatives of 2,5-diaryl-1,3-oxazole are capable of isomerization via the excited state proton transfer (ESIPT) reaction ( Fig. 1): hydroxyl group in the ortho-position of the lateral benzene ring acts as protonodonor and the nitrogen atom of oxazole ring acts as proton acceptor [6][7][8][9][10][11][12]. The result of the ESIPT reaction is the formation of phototautomeric form (T*), fluorescent in significantly longer wavelengths in comparison with the initial form (N*) [6][7][8][9][10][11][12].…”

“…Ortho-hydroxy derivatives of 2,5-diaryl-1,3-oxazole have been chosen for the study because of their high sensitivity to the parameters of the environment, such as polarity, viscosity and hydrogenbonding ability [6][7][8][9][10][11][12]. In the excited state the ortho-hydroxy derivatives of 2,5-diaryl-1,3-oxazole are capable of isomerization via the excited state proton transfer (ESIPT) reaction ( Fig.…”

“…The result of the ESIPT reaction is the formation of phototautomeric form (T*), fluorescent in significantly longer wavelengths in comparison with the initial form (N*) [6][7][8][9][10][11][12]. The position and intensity of the fluorescence of each form depend not only on the chemical structure, but also on the parameters of the molecule microenvironment [6][7][8][9][10][11][12].…”

“…Synthesis and purification of 2-(2-OH-phenyl)-5-phenyl-1,3-oxazole, 2-(2-OH-phenyl)-5-(4-phenyl-phenyl)-1,3-oxazole and 2-(2-OH-phenyl)-9,10-phenantr-1,3-oxazole were described elsewhere [6,7]. Dimethylsulfoxide, glycerol and 1,2-propanediol were from "Sigma-Aldrich Russia".…”