Excited state intramolecular proton transfer in 2-(2′-hydroxyphenyl)-3H-imidazo[4,5-b]pyridine: effect of solvents

Krishnamoorthy, G.; Dogra, Sneh K.

doi:10.1016/s0022-2313(00)00244-1

Cited by 32 publications

(54 citation statements)

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“…Furthermore, the study of this complexation may be useful in understanding the mechanism of drug action and the drug-receptor interactions [7][8][9][10] . CT complexation is also of great importance in many applications and fields, such as surface chemistry, electrically conductive materials, organic semiconductors, second-order nonlinear optical activity, and in nonlinear optical material [11][12][13][14] . As part of our continuing interest in investigating CT interactions, synthesis, characterization, and applications [15][16][17][18] , we focused this current study on the following objectives: (1) synthesize the CT complexes of picric acid (PA) acceptor with different nitrogen moieties (TEA, Hyd, TSC, Phy, and Pyr); (2) obtain the complexation stoichiometry using spectrophotometric titration and CHN elemental analysis; (3) calculate the spectroscopic data using the 1:1 and 1:2 Benesi-Hildebrand equations; (4) characterize the synthesized complexes structurally via IR, Raman, 1 H NMR, and UV-Vis spectroscopy; (5) study the thermal decomposition behaviour of the reported complexes using thermogravimetric analysis; (6) determine the kineticthermodynamic parameters (E * , A, ∆S * , ∆H * , and ∆G * ) using Coats-Redfern and Horowitz-Metzger equations; and (7) observe the microstructure characteristics of the reported complexes using OLM technique.…”

Section: Introductionmentioning

confidence: 99%

Charge-transfer interactions between nitrogen moieties as a basis for different drugs with a picric acid acceptor

Refat¹,

Saad²,

Eldaroti³

et al. 2016

ScienceAsia

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The present study investigated and compared the complexation properties of different nitrogen moieties as donors with picric acid as the acceptor. The moieties were triethylamine (TEA), hydrazine (Hyd), thiosemicarbazide (TSC), phenylhydrazine (Phy), and pyridine (Pyr). The composition and stoichiometry of the synthesized complexes were verified by spectrophotometric titration and elemental analysis. The formed complexes were characterized using IR, Raman, 1 H NMR, and UV-Vis spectroscopy, and CHN elemental analysis. Thermogravimetric experiments were carried out to investigate the thermal properties of the complexes. The microstructure properties of these complexes were investigated using optical light microscope (OLM). The donation from the nitrogen moieties to the picric acid acceptor in decreasing order was found to be Hyd > TEA > TSC > Phy > Phr. Interestingly, the thermal degradation of the TSC complex led to sulphur atoms remaining as a final residual. The OLM micrograph patterns indicate the formation of high quality coloured crystals.

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Section: Introductionmentioning

confidence: 99%

Charge-transfer interactions between nitrogen moieties as a basis for different drugs with a picric acid acceptor

Refat¹,

Saad²,

Eldaroti³

et al. 2016

ScienceAsia

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“…The single red-shifted (higher wavelength) and blue-shifted (shorter wavelength) emission bands that appear in almost all fluorescence emission spectra are ascribed to the excited ceto tautomer (ESIPT band) and the excited enol conformer (normal band), respectively. Other conformational species that can be better stabilized in the excited state in the solvent were also related by Krishnamoorthy and Dogra 46,47 for similar benzazole compounds.…”

Section: Photophysical Propertiesmentioning

confidence: 59%

Water-Soluble Benzazole Dyes Fluorescent by ESIPT: Structural Characterization, Photophysical Properties and Its Application as a Probe for Direct Staining of Helminths

Barros¹,

Marques²,

Stéfani³

2018

J. Braz. Chem. Soc.

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A series of four water-soluble benzazole dyes that emit fluorescence by the excited state intramolecular proton transfer (ESIPT) mechanism were structurally characterized by Fourier transform infrared spectroscopy (FTIR), 1 H and 13 C nuclear magnetic resonance (NMR) attached proton test (APT) and mass spectrometry. Their photophysical properties were systematically studied by UV-absorption and fluorescence emission. Some photophysical parameters were obtained by semi-empirical PM3 and ZINDO methods, and related to experimental photophysical data. Changes in the absorption and fluorescence emission spectra as well as conformational equilibrium between different species were investigated in solvents of different polarities and under different pH conditions. These benzazole dyes emit dual fluorescence emission in the blue-orange region with a Stokes shift between 2617-12337 cm-1. In general, these dyes are potentially interesting for studies of biological systems in an aqueous environment due to the presence of groups that increase aqueous solubility and reactivity with biomolecules. The present dyes were successfully used as new probes by means of direct staining of larvae. The obtained results indicate that these fluorescent dyes permit a quick, easy and selective visualization of larvae.

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“…The photophysical behavior of HPIP in different solvents has been thoroughly studied, [25][26][27] but few results have been published for HPIP in aqueous solution. [30] Due to its low quantum yield in aqueous solution, most of the studies have been performed with the dye dissolved in a mixture of water with 25 % of ethanol to increase its solubility.…”

Section: Photophysical Behavior Of Hpip In Physiologically Relevant Amentioning

confidence: 99%

“…It has been previously shown that the fluorescent properties of these socalled normal (N) conformers (N intra and N inter ) are significantly different and that their relative equilibrium populations are very sensitive to the environment. [25][26][27][28] Light absorption by the N intra conformer triggers an excited-state intramolecular proton transfer (ESIPT) process that yields a new zwitterionic species (tautomer T, see Scheme 1). T emits with an extremely large redshift (l em % 480 nm) compared with the emission band of the N inter conformer, which emits with normal Stokes shift (l em % 380 nm).…”

Section: Introductionmentioning

confidence: 99%

Towards Ratiometric Sensing of Amyloid Fibrils In Vitro

Freire

Rodríguez‐Prieto

Rodríguez

et al. 2015

Chemistry A European J

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The aggregation of amyloid-β peptide and its accumulation in the human brain has an important role in the etiology of Alzheimer's disease. Thioflavin T has been widely used as a fluorescent marker for these amyloid aggregates. Nevertheless, its complex photophysical behavior, with strong wavelength dependencies of all its fluorescence properties, requires searching for new fluorescent probes. The use of 2-(2'-hydroxyphenyl)imidazo[4,5-b]pyridine (HPIP), which shows two emission bands and a rich excited-state behavior due to the existence of excited-state intramolecular processes of proton transfer and charge transfer, is proposed. These properties result in a high sensitivity of HPIP fluorescence to its microenvironment and cause a large differential fluorescence enhancement of the two bands upon binding to aggregates of the amyloid-β peptide. Based on this behavior, a very sensitive ratiometric method is established for the detection and quantification of amyloid fibrils, which can be combined with the monitoring of fluorescence anisotropy. The binding selectivity of HPIP is discussed on the basis of the apparent binding equilibrium constants of this probe to amyloid-β (1-42) fibrils and to the nonfibrillar protein bovine serum albumin. Finally, an exhaustive comparison between HPIP and thioflavin T is presented to discuss the sensitivity and specificity of these probes to amyloid aggregates and the significant advantages of the HPIP dye for quantitative determinations.

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Excited state intramolecular proton transfer in 2-(2′-hydroxyphenyl)-3H-imidazo[4,5-b]pyridine: effect of solvents

Cited by 32 publications

References 50 publications

Charge-transfer interactions between nitrogen moieties as a basis for different drugs with a picric acid acceptor

Charge-transfer interactions between nitrogen moieties as a basis for different drugs with a picric acid acceptor

Water-Soluble Benzazole Dyes Fluorescent by ESIPT: Structural Characterization, Photophysical Properties and Its Application as a Probe for Direct Staining of Helminths

Towards Ratiometric Sensing of Amyloid Fibrils In Vitro

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