Density Functional Theory Applied to Excited State Intramolecular Proton Transfer in Imidazole-, Oxazole-, and Thiazole-Based Systems

Carvalho, Flávio; Coutinho-Neto, Maurı́cio D.; Bartoloni, Fernando Heering; Homem-de-Mello, Paula

doi:10.3390/molecules23051231

Cited by 17 publications

(23 citation statements)

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“…The hydroxy group in 15 d was located in the position close to the nitrogen atom of the thiazole ring. Intermolecular hydrogen‐bonding interaction was not observed, but the bond length of N1−H21 was 1.891 Å, which suggested that ESIPT was expected to take place with 15 d . The presence of the intramolecular hydrogen‐bonding interactions is further supported by 1 H NMR spectra.…”

Section: Figurementioning

confidence: 93%

2‐(2‐Hydroxyphenyl)‐5‐aminothiazoles: Synthesis and Properties Involving Dual Emissions

et al. 2019

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2-(2-Hydroxyphenyl)-5-aminothiazoles were prepared by two different methods to elucidate their photophysical properties. The first synthetic method involved the addition of thioamide dianions derived from secondary thioamides and nBuLi to thioforamides. Alternatively, Pdcatalyzed sequential addition of aromatic groups and diarylamines to commercially available thiazoles led to the precursors of the desired thiazoles. The molecular structures of the resulting thiazoles were determined by X-ray analyses. The thiazoles showed dual-emission in cyclohexane and in the solid state.[a] Prof.

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Section: Figurementioning

confidence: 93%

2‐(2‐Hydroxyphenyl)‐5‐aminothiazoles: Synthesis and Properties Involving Dual Emissions

et al. 2019

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“…Non‐normalized fluorescence (FL) spectra ( λ ex = 296 nm) for 1 (top, black line) and 2 (bottom, black line), compared to 2 − at different HO − concentrations (colored lines). In MeOH at 25°C; = 3.22 × 10 −5 mol L −1 ; using KOH as hydroxide source; [HO − ] = 0.64 (A), 2.63 (B) and 6.45 (C) mmol L − 1 …”

Section: Discussionmentioning

confidence: 99%

“…The triphenylimidazole structural framework has been intensely studied throughout the years, by many different research groups, due to its fluorescence (FL) and chemiluminescence (CL) properties. The typical direct CL of 2,4,5‐triphenylimidazole (also known as lophine) with oxygen in an alkaline media, first described by Radziszewski in 1877, was studied mainly to elucidate its reaction mechanism .…”

Section: Introductionmentioning

confidence: 99%

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The decomposition of triphenylimidazole‐para‐acetate follows specific base catalysis and can be conveniently followed by fluorescence

et al. 2019

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The kinetics of the decomposition reaction of 4-(4,5-diphenyl-1H-imidazol-2-yl)phenyl acetate (1) in basic alcoholic media was investigated, using a simple fluorescence (FL) spectrophotometric procedure. The process was conveniently studied using FL, since the triphenylimidazole-derived ester 1 and its reaction products (the corresponding phenol 2 and phenolate 2 − ) are all highly fluorescent (Φ FL > 37%). By carefully selecting excitation and emission wavelengths, observed rate constants k 1 in the order of 10 −3 to 10 −2 s −1 were obtained from either reactant consumption (λ ex = 300 nm, λ em = 400 nm) or product formation (λ ex = 350 nm, λ em = 475 nm); these were shown to be kinetically equivalent. Intensity-decay time profiles also gave a residual FL intensity parameter, shown to be associated to the distribution of produced species 2 and 2 − , according to the basicity of the medium. Studying the reaction in both methanol (MeOH) and isopropanol (iPrOH), upon addition of HO − , provided evidence that the solvent's conjugate base is the active nucleophilic species.When different bases were used (tBuO − , HO − , DBU and TEA), bimolecular rate constants k bim ranging from 4.5 to 6.5 L mol −1 s −1 were obtained, which proved to be non-dependent on the base pK aH , suggesting specific base catalysis for the decomposition of 1 in alcoholic media. KEYWORDS imidazole, kineticslight emissionlophine, rate constant 1 | INTRODUCTIONThe triphenylimidazole structural framework has been intensely studied throughout the years, by many different research groups, due to its fluorescence (FL) [1][2][3][4][5][6][7][8][9] and chemiluminescence (CL) [10][11][12][13][14][15][16][17][18][19][20][21][22] properties. The typical direct CL of 2,4,5-triphenylimidazole (also known as lophine) with oxygen in an alkaline media, first described by Radziszewski in 1877, [23] was studied mainly to elucidate its reaction mechanism. [11][12][13][18][19][20][21][22]24] However, lophine and its derivatives were also applied in other CL systems, being used as activators of the peroxyoxalate reaction [10] or enhancers of the luminol transformation. [25][26][27] In part, the vast array of application of these molecules, from FL to CL measurements, depends on the high FL quantum yields (Φ FL > 0.1) presented by them. [1][2][3][4][5][6][7][8][9][10]17,[24][25][26][27] In 1993, Kuroda et al. reported that triphenylimidazole-para-acetate (1, IUPAC name 4-(4,5-diphenyl-1H-imidazol-2-yl)phenyl acetate), as well as another three ester analogs based on pertinent fatty acids, could be applied on the evaluation of lipase activity through FL measurements. [8] Although ester 1 itself was not the most suitable for interaction with the lipase, it was primarily used to define the methodology for activity determination. Briefly, the method consisted on hydrolyzing the ester with the enzyme, followed by separation and FL

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“…The most remarkable photophysical property of the ESIPT chromophores is the large fluorescence Stokes shift. The presence of this property in compounds showing ESIPT phenomena, together with the dual emission makes them quite exploited as OLED materials, spectroscopy tools, and fluorescence probes in biology [ 9 , 10 , 11 , 12 , 13 ]. However, the ESIPT process in 2-acetyl-1-naphthol has been in controversy for long, primarily because of its quantitative ESIPT conversion in most solution conditions and also due to small Stokes shift of the ESIPT products (keto type prototautomer) compared to those products in other typical ESIPT molecules [ 1 , 14 ].…”

Section: Introductionmentioning

confidence: 99%

Structural and Energetic Insights on Two Dye Compounds: 1-Acetyl-2-Naphthol and 2-Acetyl-1-Naphthol

Freitas

Silva

2020

Molecules

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The energy involved in the structural switching of acyl and hydroxyl substituents in the title compounds was evaluated combining experimental and computational studies. Combustion calorimetry and Knudsen effusion techniques were used to determine the enthalpies of formation, in the crystalline state, and of sublimation, respectively. The gas-phase enthalpy of formation of both isomers was derived combining these two experimental data. Concerning the computational study, the G3(MP2)//B3LYP composite method was used to optimize and determine the energy of the isomers in the gaseous state. From a set of hypothetical reactions it has been possible to estimate the gas-phase enthalpy of formation of the title compounds. The good agreement between the experimental and computational gas-phase enthalpies of formation of the 1-acetyl-2-naphthol and 2-acetyl-1-naphthol isomers, provided the confidence for extending the computational study to the 2-acetyl-3-naphthol isomer. The structural rearrangement of the substituents in position 1 and 2 in the naphthalene ring and the energy of the intramolecular hydrogen bond are the factors responsible for the energetic differences exhibited by the isomers. The gas phase tautomeric keto « enol equilibria of the o-acetylnaphthol isomers were analyzed using the Boltzmann’s distribution.

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Density Functional Theory Applied to Excited State Intramolecular Proton Transfer in Imidazole-, Oxazole-, and Thiazole-Based Systems

Cited by 17 publications

References 87 publications

2‐(2‐Hydroxyphenyl)‐5‐aminothiazoles: Synthesis and Properties Involving Dual Emissions

2‐(2‐Hydroxyphenyl)‐5‐aminothiazoles: Synthesis and Properties Involving Dual Emissions

The decomposition of triphenylimidazole‐para‐acetate follows specific base catalysis and can be conveniently followed by fluorescence

Structural and Energetic Insights on Two Dye Compounds: 1-Acetyl-2-Naphthol and 2-Acetyl-1-Naphthol

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