A quantum-chemical insight into the tunable fluorescence color and distinct photoisomerization mechanisms between a novel ESIPT fluorophore and its protonated form

Yuan, Huijuan; Feng, Songyan; Wen, Keke; Zhu, Qiuling; An, Beibei; Guo, Xugeng; Zhang, Jinglai

doi:10.1016/j.saa.2017.04.025

Cited by 22 publications

(6 citation statements)

References 49 publications

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“…In other words, the intramolecular H-bonds in 3 and 2, which has a CH 2 OH group and a phenyl ring based on phenol-thiazole molecule, are the strongest and weakest H-bonds among three molecules, respectively. Generally speaking, a strong intramolecular H-bonding in the S 1 enol form would promote ESIPT to occur since strong H-bonding only need a small structural adjustment and a low potential barrier during the enol-keto tautomerization process [69,70]. It can be predicted that the ESIPT processes in 3 and 2 would be the easiest and hardest among molecules 1-3.…”

Section: Structures Analysismentioning

confidence: 99%

Theoretical investigations on forward–backward ESIPT processes of three fluorophores deriving from 2-(2′-hydroxyphenyl)thiazole

Liang

Fang

2021

Photochem Photobiol Sci

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The photophysical properties and excited-state intramolecular proton transfer (ESIPT) processes for 2-(2′-hydroxyphenyl)-4-chloromethylthiazole (1), 2-(2′-hydroxyphenyl)-4-phenylthiazole (2), 2-(2′-hydroxyphenyl)-4-hydroxymethyl-thiazole (3) were studied at the TD-B3PW91/6-31 + G(d, p)/IEFPCM level. The structures of 1-3 were fully optimized and the corresponding structural parameters, infrared spectra and electron densities in the ground (S 0 ) and the first excited (S 1 ) states were analyzed. The calculated absorption and fluorescence wavelengths of 1-3 reproduced the experimental data. The potential energy curves of the S 0 and S 1 states were built and the ESIPT processes were clarified. Our results showed that the intramolecular H-bonds of 3 and 2 in the S 1 state were the strongest and the weakest, respectively, and then the ESIPT potential barriers of 3 and 2 were the lowest and highest, respectively. Among the three phenol-thiazole type probes, the compound 2 with phenyl ring group at the 4 position of the thiazole ring had the larger π-conjugation, and had the higher ESIPT potential barrier at the same time. The corresponding compound 1 and 3 with CH 2 Cl and CH 2 OH had the lower ESIPT barrier.

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Section: Structures Analysismentioning

confidence: 99%

Theoretical investigations on forward–backward ESIPT processes of three fluorophores deriving from 2-(2′-hydroxyphenyl)thiazole

Liang

Fang

2021

Photochem Photobiol Sci

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“…Although single‐crystal X‐ray analysis of BTImP‐HCl supports a twisted geometry of the protonated BTImP, recent DFT calculations by Zhang et al. suggest that a coplanar geometry of Im, BT, and the central phenol ring is preferential, in which the HIm + proton is H‐bonded to the oxygen atom of the phenolic hydroxy group . The reason for this discrepancy could be that their calculations did not include the influence of the anion.…”

Section: Discussionmentioning

confidence: 98%

Color Changes of a Full‐Color Emissive ESIPT Fluorophore in Response to Recognition of Certain Acids and Their Conjugate Base Anions

Tsuchiya

Sakai

Kawano

et al. 2018

Chemistry A European J

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2-(1,3-Benzothiazol-2-yl)-4-methoxy-6-(1,4,5-triphenyl-1H-imidazol-2-yl)phenol (BTImP) is an excited-state intramolecular proton transfer (ESIPT) fluorophore, containing an acid-stimuli-responsive intramolecular hydrogen bond (H-bond) that can switch from the central phenolic proton to the imidazole (Im) or benzothiazole (BT) nitrogen atoms. Here, we demonstrate that BTImP shows full-color (red, green, blue, and white) emission upon the addition of different concentrations of HClO or, with time, after the addition of HBF . It also shows thermally dependent color changes from pink through white to blue in a narrow temperature range of 25-60 °C. H and N NMR measurements suggest that, after the green fluorescent BTImP is protonated at its Im nitrogen atom, a conjugate base anion coordinates to the imidazolium (HIm ) proton, forming two types of complexes with different coordination states. One state shows a significantly Stokes-shifted red emission resulting from ESIPT at the BT side, whereas the other shows a typical Stokes-shifted blue emission, probably caused by interaction of the anion with the phenolic proton, which breaks the H-bond on the BT side. BF and ClO are effective in forming such a blue emitter, whereas Cl and PF are not; this behavior depends on whether the anion can fit into the bidentate binding site consisting of HIm and the phenolic hydroxy group.

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“…Due to the large variety of emissive excited states, the emission of ESIPT-capable molecules is sensitive to various stimuli. − The breaking of the intramolecular hydrogen bond due to the interaction of the ESIPT site of the molecule with other molecules or ions or due to deprotonation causes strong changes in the luminescence response of ESIPT-capable molecules. The protonation of ESIPT-capable molecules can proceed at the hydrogen bond-accepting atom switching the ESIPT reaction off or at other heteroatoms leading to modulating ESIPT and ESIPT-coupled luminescence. − Binding metal ions by ESIPT dyes which is accompanied by the deprotonation in most cases (only rare examples of ESIPT-capable metal complexes are known) ,,− also results in strong changes of emission. − This sensitivity allows one to switch the emission of ESIPT-capable molecules between various emission mechanisms and makes them a multivariate platform for the design of stimuli-responsive emissive materials, probes, and sensors.…”

Section: Introductionmentioning

confidence: 99%

Complexes on the Base of a Proton Transfer Capable Pyrimidine Derivative: How Protonation and Deprotonation Switch Emission Mechanisms

Shekhovtsov,

Vorob’eva,

Nikolaenkova

et al. 2023

Inorg. Chem.

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A rare example of pyrimidine-based ESIPT-capable compounds, 2-(2-hydroxyphenyl)-4-(1H-pyrazol-1-yl)-6-methylpyrimidine (HL H ), was synthesized (ESIPT�excited state intramolecular proton transfer). Its reactions with zinc(II) salts under basic or acidic conditions afforded a dinuclear [Zn 2 L H 2 Cl 2 ] complex and an ionic (H 2 L H ) 4 [ZnCl 4 ] 2 • 3H 2 O solid. Another ionic solid, (H 2 L H )Br, was obtained from the solution of HL H acidified with HBr. In both ionic solids, the H + ion protonates the same pyrimidinic N atom that accepts the O−H•••N intramolecular hydrogen bond in the structure of free HL H , which breaks this hydrogen bond and switches off ESIPT in these compounds. This series of compounds which includes neutral HL H molecules and ionic (L H ) − and (H 2 L H ) + species allowed us to elucidate the impact of protonation and coordination coupled deprotonation of HL H on the photoluminescence response and on altering the emission mechanism. The neutral HL H compound exhibits yellow emission as a result of the coexistence of two radiative decay channels: (i) T 1 → S 0 phosphorescence of the enol form and (ii) anti-Kasha S 2 → S 0 fluorescence of the keto form, which if feasible due to the large S 2 −S 1 energy gap. However, owing to the efficient nonradiative decay through an energetically favorable conical intersection, the photoluminescence quantum yield of HL H is low. Protonation or deprotonation of the HL H ligand results in the significant blue-shift of the emission bands by more than 100 nm and boosts the quantum efficiency up to ca. 20% in the case ofand (H 2 L H )Br have the same (H 2 L H ) + cation in the structures, their emission properties differ significantly, whereas (H 2 L H )Br shows dual emission associated with two radiative decay channels: (i) S 1 → S 0 fluorescence and (ii) T 1 → S 0 phosphorescence, (H 2 L H ) 4 [ZnCl 4 ] 2 •3H 2 O exhibits only fluorescence. This difference in the emission properties can be associated with the external heavy atom effect in (H 2 L H )Br, which leads to faster intersystem crossing in this compound. Finally, a huge increase in the intensity of the phosphorescence of (H 2 L H )Br on cooling leads to pronounced luminescence thermochromism (violet emission at 300 K, sky-blue emission at 77 K).

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A quantum-chemical insight into the tunable fluorescence color and distinct photoisomerization mechanisms between a novel ESIPT fluorophore and its protonated form

Cited by 22 publications

References 49 publications

Theoretical investigations on forward–backward ESIPT processes of three fluorophores deriving from 2-(2′-hydroxyphenyl)thiazole

Theoretical investigations on forward–backward ESIPT processes of three fluorophores deriving from 2-(2′-hydroxyphenyl)thiazole

Color Changes of a Full‐Color Emissive ESIPT Fluorophore in Response to Recognition of Certain Acids and Their Conjugate Base Anions

Complexes on the Base of a Proton Transfer Capable Pyrimidine Derivative: How Protonation and Deprotonation Switch Emission Mechanisms

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