Benzothiazol picolin/isonicotinamides molecular switches: Expectations and reality

Georgiev, Anton; Deneva, Vera; Yordanov, Dancho; Völzer, Tim; Wolter, Steffen; Fennel, Franziska; Lochbrunner, Stefan; Antonov, Liudmil

doi:10.1016/j.molliq.2022.118968

Cited by 5 publications

(6 citation statements)

References 67 publications

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“…8–10 The excitation of such a molecule in its normal form ( N ) with light results in the transfer of the electron density from the electron-donating group to the electron-accepting one, which in turn alters the acidity and basicity of the proton-donating and proton-accepting groups and promotes the proton to transfer (excited state intramolecular proton transfer, ESIPT) affording the tautomeric form ( T ) of the molecule (Scheme 1). 11–32 If the ESIPT process is barrierless, the only form to emit is the tautomeric form. This emission is associated with dramatic reorganization of the molecular structure, resulting in large Stokes shifts.…”

Section: Introductionmentioning

confidence: 99%

Tuning ESIPT-coupled luminescence by expanding π-conjugation of a proton acceptor moiety in ESIPT-capable zinc(ii) complexes with 1-hydroxy-1H-imidazole-based ligands

et al. 2022

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Section: Introductionmentioning

confidence: 99%

Tuning ESIPT-coupled luminescence by expanding π-conjugation of a proton acceptor moiety in ESIPT-capable zinc(ii) complexes with 1-hydroxy-1H-imidazole-based ligands

et al. 2022

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“…Bearing in mind that both (amino and imino) tautomers have different conjugation systems and different polarity, they can easily be detected by their UV-Vis absorption spectra, which should be solvent-dependent [ 55 ]. The amino–imino proton exchange proceeds through a four-membered ring, which leads, without solvent assistance, to an increase of the transition state energy [ 56 ] and makes the process possible to be detected by NMR spectroscopy. Recently, the transition state through the four-membered ring in 1,3,5-triazine derivatives has been estimated by DFT calculation to be about 50 kcal/mol [ 57 ].…”

Section: Resultsmentioning

confidence: 99%

Structure and Conformational Mobility of OLED-Relevant 1,3,5-Triazine Derivatives

et al. 2023

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A series of OLED-relevant compounds, consisting of 1,3,5-triazine core linked to various aromatic arms by amino group, has been synthesized and characterized. The studied compounds exist in solution as a mixture of two conformers, a symmetric propeller and asymmetric conformer, in which one of the aromatic arms is rotated around the C-N bond. At temperatures below −40 °C, the VT NMR spectra in DMF-d7 are in a slow exchange regime, and the signals of two conformers can be elucidated. At temperatures above 100 °C, the VT NMR spectra in DMSO-d6 are in a fast exchange regime, and the averaged spectra can be measured. The ratio of symmetric and asymmetric conformers in DMF-d7 varies from 14:86 to 50:50 depending on the substituents. The rotational barriers of symmetric and asymmetric conformers in DMF-d7 were measured for all compounds and are in the interval from 11.7 to 14.7 kcal/mol. The ground-state energy landscapes of the studied compounds, obtained by DFT calculations, show good agreement with the experimental rotational barriers. The DFT calculations reveal that the observed chemical exchange occurs by the rotation around the C(1,3,5-triazine)-N bond. Although some of the compounds are potentially tautomeric, the measured absorption and emission spectra do not indicate proton transfer neither in the ground nor in the excited state.

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Section: Introductionmentioning

confidence: 99%

“…1 H -Imidazoles, 1,3-oxazoles, 1,3-thiazoles and their benzannulated congeners are often used in the design of ESIPT-fluorophores [ 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 ]. Normally, when decorated with such proton-donating groups as unsubstituted or substituted 2-hydroxyphenyl groups in the α-position to aza-atoms, their free nitrogen atoms act as proton acceptors during the ESIPT process [ 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 ]. Recently we proposed a new approach in the design of imidazole-based ESIPT-fluorophores in which we switched the role of the imidazole cycle to the one of a proton donor by introducing the hydroxy group in the position 1 and the pyridin-2-yl group in the position 2 of the imidazole ring [ 83 , 84 , 85 , 86 , 87 ].…”

Section: Introductionmentioning

confidence: 99%

ESIPT-Capable 4-(2-Hydroxyphenyl)-2-(Pyridin-2-yl)-1H-Imidazoles with Single and Double Proton Transfer: Synthesis, Selective Reduction of the Imidazolic OH Group and Luminescence

et al. 2023

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1H-Imidazole derivatives establish one of the iconic classes of ESIPT-capable compounds (ESIPT = excited state intramolecular proton transfer). This work presents the synthesis of 1-hydroxy-4-(2-hydroxyphenyl)-5-methyl-2-(pyridin-2-yl)-1H-imidazole (LOH,OH) as the first example of ESIPT-capable imidazole derivatives wherein the imidazole moiety simultaneously acts as a proton acceptor and a proton donor. The reaction of LOH,OH with chloroacetone leads to the selective reduction of the imidazolic OH group (whereas the phenolic OH group remains unaffected) and to the isolation of 4-(2-hydroxyphenyl)-5-methyl-2-(pyridin-2-yl)-1H-imidazole (LH,OH), a monohydroxy congener of LOH,OH. Both LOH,OH and LH,OH demonstrate luminescence in the solid state. The number of OH···N proton transfer sites in these compounds (one for LH,OH and two for LOH,OH) strongly affects the luminescence mechanism and color of the emission: LH,OH emits in the light green region, whereas LOH,OH luminesces in the orange region. According to joint experimental and theoretical studies, the main emission pathway of both compounds is associated with T1 → S0 phosphorescence and not related to ESIPT. At the same time, LOH,OH also exhibits S1 → S0 fluorescence associated with ESIPT with one proton transferred from the hydroxyimidazole moiety to the pyridine moiety, which is not possible for LH,OH due to the absence of the hydroxy group in the imidazole moiety.

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Benzothiazol picolin/isonicotinamides molecular switches: Expectations and reality

Cited by 5 publications

References 67 publications

Tuning ESIPT-coupled luminescence by expanding π-conjugation of a proton acceptor moiety in ESIPT-capable zinc(ii) complexes with 1-hydroxy-1H-imidazole-based ligands

Tuning ESIPT-coupled luminescence by expanding π-conjugation of a proton acceptor moiety in ESIPT-capable zinc(ii) complexes with 1-hydroxy-1H-imidazole-based ligands

Structure and Conformational Mobility of OLED-Relevant 1,3,5-Triazine Derivatives

ESIPT-Capable 4-(2-Hydroxyphenyl)-2-(Pyridin-2-yl)-1H-Imidazoles with Single and Double Proton Transfer: Synthesis, Selective Reduction of the Imidazolic OH Group and Luminescence

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