Experimental and theoretical investigation of ground state intramolecular proton transfer (GSIPT) in salicylideneaniline Schiff base derivatives in polar protic medium

Das, Bijoya; Chakraborty, Amrita; Chakraborty, Shamik

doi:10.1016/j.saa.2019.117443

Cited by 25 publications

(5 citation statements)

References 55 publications

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“…Therefore, there may be coexistence of these conformers in S 0 state. Hence, we believe that both tautomeric forms i. e., 1–3 (E) and 1–3 (K) would contribute to the absorption spectra. In addition, it is also suspected that the cyanide interacts with 1E via hydrogen bond formation (to form 2‐HB) followed by deprotonation process (to form 4D).…”

Section: Resultsmentioning

confidence: 96%

DFT/TD‐DFT Based Study to Decipher the Proton Transfer Process in Anion Sensing Mechanism of NTS Molecule

2020

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In the present work, we have performed DFT/TD-DFT studies on NTS [1-(((4-(benzo[d]thiazol-2-yl) phenyl) imino) methyl) naphthalen-2-ol, referred to as 1E] to investigate the cyanide and fluoride anion sensing mechanism via proton transfer process in the ground and excited state. The potential energy curve for the proton transfer in ground (GSIPT) and excited state (ESIPT) suggests that, in case of NTS molecule, keto and enol form co-exist. Based on the pattern of addition of cyanide on NTS, nucleophilic addition supports GSIPT rather ESIPT. However, fluoride addition showed both GSIPT and barrier less ESIPT processes followed by the deprotonation. From the energy calculations, we have observed that the cyanide addition (nucleophilic) block ICT character due to similar geometries in the ground and excited state, along with the interruption in the conjugation of the molecule. But, in the case of fluoride added product, ICT character was observed owing to the change in geometry of the corresponding states (ground and excited). ESIPT process has also been explained in terms of HOMO-LUMO electron density, potential energy surfaces and NBO analysis. ChemistrySelectFull Papers Scheme 3. Schematic diagram of cyanide anion sensing mechanism.Scheme 4. Schematic diagram of fluoride anion sensing mechanism.

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Section: Resultsmentioning

confidence: 96%

DFT/TD‐DFT Based Study to Decipher the Proton Transfer Process in Anion Sensing Mechanism of NTS Molecule

2020

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“…Absorption spectra of HBAP, in both these solvents, consist of two π–π* bands with maxima (

λ_{\max}^{abs}

) at 350 and 445 nm, ascribed to enol and keto forms, respectively (Figure 2A). 35 The fluorescence spectra are Stokes shifted, with emission maxima (

λ_{\max}^{em}

) at 540 nm in both the solvents (Figure 2A and Figure S3A). For both the Schiff bases, the fluorescence quantum yield is miniscule (

ϕ_{f}

= 0.001 in HBAP and 0.0002 for salbn) in methanol, but increases to

ϕ_{f}

= 0.008 in glycerol (Figure 2B), as segmental motions are hindered in the solvent with significantly higher viscosity.…”

Section: Resultsmentioning

confidence: 99%

Modulation of fluorescence and phosphorescence of organoboron compounds from ortho‐substituted phenolic Schiff bases by structural modification

Chowdhury,

Dasgupta,

Gaur

et al. 2024

Photochem & Photobiology

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Light emission from organoboron compounds of Schiff bases is found to depend strongly on their chemical structure. Two of these compounds (OB1 and OB2), which contain a benzene ring between the Schiff base moieties, exhibit weak fluorescence in methanol, with marked viscosity dependence. Fluorescence lifetimes of these compounds are in picosecond timescale, as determined by femtosecond optical gating (FOG). A significant enhancement in fluorescence intensity and lifetime is observed at 77 K, indicating the operation of an activated nonradiative process. Using fluorescence lifetime imaging microscopy (FLIM), OB1 and OB2 are shown to be potential membrane probes. The third (OB3), which is devoid of this benzene ring, exhibits relatively stronger fluorescence with nanosecond lifetimes at room temperature. No viscosity dependence is observed in this case. The emission spectrum at 77 K is markedly more intense and exhibits an additional red shifted structured feature, which persists for a few seconds. Hence, OB3 seems to have greater promise not only as fluorescent probe but also for light harvesting. The marked improvement of the light emission properties of OB3 compared with OB1 and OB2 is likely to serve as a pointer for the design of Schiff base‐derived organoboron luminophores with diverse potential applications.

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“…But, in polar solvents it exhibits dual emission at around 365 nm and 500 nm which were ascribed to enol emission and keto emission respectively (figure S19) [28]. The transition from single emission to dual emission should be attributed to the solvation of the hydroxyl group in polar solvents, which partly break the intramolecular hydrogen bonds and thus disturb the ESIPT process [35][36][37][38][39][40][41].…”

Section: Emission In Solution Statementioning

confidence: 99%

Bright ESIPT emission from 2,6-di(thiazol/oxazol/imidazol-2-yl)phenol derivatives in solution, aggregation and solid states

Chen,

Niu,

Wang

2024

Methods Appl. Fluoresc.

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Most luminophores often suffer from the problem of aggregation-caused quenching (ACQ) or fluorescence disappearance in dilute solution. It is significant to bridge the gap between ACQ and AIE. In this work, a facile but effective strategy was proposed for the fabrication of always-on luminophores based on the excited state intramolecular proton transfer (ESIPT) mechanism, and six luminophores emitting bright fluorescence in solution, aggregation and solid states were synthesized from 5-tert-butyl-2-hydroxyisophthalaldehyde. All these ESIPT systems show only keto emission owing to their congested structures which block the breakage of intramolecular hydrogen bond (O–H•••N) by solvation, and subsequently make enol emission impossible. Three of these luminophores are prone to convert into the corresponding phenolate anions emitting blue-shifted emission, which enable them to sense pH variation in the weakly basic range. Furthermore, white-light emission was achieved by combining two of them which show complementary-color fluorescence, and one of them was utilized for bioimaging of living Hela cells and the high-resolution image was obtained.

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Experimental and theoretical investigation of ground state intramolecular proton transfer (GSIPT) in salicylideneaniline Schiff base derivatives in polar protic medium

Cited by 25 publications

References 55 publications

DFT/TD‐DFT Based Study to Decipher the Proton Transfer Process in Anion Sensing Mechanism of NTS Molecule

DFT/TD‐DFT Based Study to Decipher the Proton Transfer Process in Anion Sensing Mechanism of NTS Molecule

Modulation of fluorescence and phosphorescence of organoboron compounds from ortho‐substituted phenolic Schiff bases by structural modification

Bright ESIPT emission from 2,6-di(thiazol/oxazol/imidazol-2-yl)phenol derivatives in solution, aggregation and solid states

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