Exploration of the ESIPT process in a newly designed potential bioactive thiosemicarbazone Schiff base: Spectroscopic analysis accompanied by molecular optimization and crystallographic study

Ganorkar, Kapil; Mukherjee, Soham; Wankar, Sneha; Joshi, Ritika; Das, Chayan; Ghosh, Sujit Kumar

doi:10.1016/j.jphotochem.2018.11.002

Cited by 16 publications

(22 citation statements)

References 56 publications

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“…In nonpolar solvents, upon photoexcitation at its λ max abs , DAHTS exhibits three different “types” of fluorescence emission peaks of weak intensity (Figure A). First, the primary emission peaks have a vibronic constituent (centered at 405, 421, and 443 nm) that may arise from the monomeric and dimeric forms of DAHTS ( vide infra ), while the second “type” of fluorescence emission peaks that appears as a first shoulder around the 480 nm region presumably stems from the keto-amine tautomer of the molecule . This tautomer is obtained by the excited-state intramolecular proton transfer (ESIPT) reaction that takes place between the hydroxyl “O” atom and azomethine “N” atom of DAHTS, as reported elsewhere by our group .…”

Section: Resultsmentioning

confidence: 99%

“…First, the primary emission peaks have a vibronic constituent (centered at 405, 421, and 443 nm) that may arise from the monomeric and dimeric forms of DAHTS ( vide infra ), while the second “type” of fluorescence emission peaks that appears as a first shoulder around the 480 nm region presumably stems from the keto-amine tautomer of the molecule . This tautomer is obtained by the excited-state intramolecular proton transfer (ESIPT) reaction that takes place between the hydroxyl “O” atom and azomethine “N” atom of DAHTS, as reported elsewhere by our group . In addition, another shoulder at around ∼535 nm is observed, pointing its origin from DAHTS aggregates (SI, Figure S2).…”

Section: Resultsmentioning

confidence: 99%

“…As the alteration in the the decay curve indicates the change in the number of excited-state species of DAHTS, it justifies the absence of the ESIPT process in polar protic solvents. As a result, the shortest-lived keto-amine tautomer disappears due to the formation of an extensive intermolecular H-bonding network between DAHTS and solvent molecules . Particularly in alcohols, the DAHTS monomer, with a lifetime of τ 1 ∼ 2 ns becomes the major contributor in the excited state.…”

Section: Resultsmentioning

confidence: 99%

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Switching of the Polarity-Sensitive Aggregation Pattern of a Thiosemicarbazone-Based Anticancer Luminophore and Its Involvement in Cellular Apoptosis of the Human Lung Cancer Cell Line

et al. 2023

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Elucidation of the photophysical and biochemical properties of small molecules can facilitate their applications as prospective therapeutic imaging (theragnostic) agents. Herein, we demonstrate the luminescence behavior of a strategically designed potential therapeutic thiosemicarbazone derivative, (E)-1-(4-(diethylamino)-2-hydroxybenzylidene)-4,4-dimethylthiosemicarbazide (DAHTS), accompanied by the illustration of its solvation and solvation dynamics using spectroscopic techniques and exploring its promising antitumor activities by adopting the necessary biochemical assays. Solvent-dependent photophysical properties, namely UV−vis absorption, fluorescence emission, and excitation profiles, concentrationdependent studies, and time-resolved fluorescence decays, serve as footprints to explain the existence of DAHTS monomers, its excitedstate intramolecular proton transfer (ESIPT) product, and dimeric and aggregated forms. The emission intensity progressively intensifies with increasing polarity and proticity of the solvents up to MeOH, but in water, a sudden dip is seen. Solvent polarity and H-bonding modulate the fluorescence behavior of the primary emission peak and significantly influence the formation of the dimer and DAHTS aggregates. The designed luminophore (DAHTS) exhibits significant antiproliferative activity against the human lung cancer (A549) cell lines with inhibitory concentrations (IC 50 ) of 16.88 and 11.92 μM for 24 and 48 h, respectively. DAHTS effectively reduces the cell viability and induces cytotoxicity with extensive morphological changes in A549 cells in the form of spikes when compared to the normal HEK cell lines. More importantly, it increases the p53 expression at the mRNA level that consolidates its potential therapeutic activity. The effect of DAHTS on apoptotic pathways against the A549 cell line has been investigated to determine its probable mechanism of cell death. Thus, the all-inclusive understanding of the photophysical properties and the necessary biochemical assays put forward important steps toward tailoring the thiosemicarbazone core structure for favorable cancer theragnostic applications in academic and pharmaceutical research.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Switching of the Polarity-Sensitive Aggregation Pattern of a Thiosemicarbazone-Based Anticancer Luminophore and Its Involvement in Cellular Apoptosis of the Human Lung Cancer Cell Line

et al. 2023

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“…The optimization was done by using Becke’s three-parameter exchange correlation functional Lee, Yang, and Parr (B3LYP) functional with a 6-31G(d) basis set. The molecular orbital optimizations (HOMO, LUMO) calculated by using time-dependent density functional theory (TD-DFT) were used for optimization of a geometry in the singlet excited state using the mentioned basis set with the polarizable continuum model (PCM) . The vertical excitations were computed using the linear response of TD-DFT with the 12 lowest singlet–singlet transitions using the aformentioned basis set and functional.…”

Section: Methodsmentioning

confidence: 99%

“…The molecular orbital optimizations (HOMO, LUMO) calculated by using time-dependent density functional theory (TD-DFT) were used for optimization of a geometry in the singlet excited state using the mentioned basis set with the polarizable continuum model (PCM). 49 The vertical excitations were computed using the linear response of TD-DFT with the 12 lowest singlet−singlet transitions using the aformentioned basis set and functional. The thermal stabilities of synthesized homo-and copolymer powders (approximately 10 mg) were investigated using thermogravimetric analysis (TGA) with a TA Instruments TGA55 Discovery series instrument under an N 2 atmosphere.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Synthesis and Characterization of Acid-Responsive Luminescent Fe(II) Metallopolymers of Rigid and Flexible Backbone N-Donor Multidentate Conjugated Ligands

et al. 2020

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In this report we have disclosed the syntheses and properties of two new conjugated organic moieties bearing the same coordination sites but possessing different backbone rigidities and rotational flexibilities. Two new metallopolymers have been synthesized from the corresponding ligands under identical reaction conditions, and they have been thoroughly characterized through different techniques to understand the effect of backbone rigidity on the evolution of different properties in these metallopolymers. A FESEM micrograph of the rigid metallopolymer confirms the formation of a rigid nanorod type structure, while long agglomerated nanofiber strands are visible on the substrate in the case of the flexible analogue. All of the newly synthesized materials are fluorescence active. An Fe(II) metallopolymer of the flexible ligand showed huge changes in emission properties in the presence of different acids and showed a possibility of it being used as a thin film acid vapor sensor. All of the materials showed reversible electrochemical activity, and both of these polymers have shown electroluminescence when an appropriate potential is applied.

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Water‐Assisted Photoinduced Tautomerization in a Potential Bioactive Semicarbazone Schiff Base

Singh,

Teena,

Ganorkar

et al. 2023

ChemistrySelect

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This article epitomizes the design and synthesis of a potential bioactive Semicarbazone Schiff base (E)‐2‐(4‐(diethylamino)‐2‐hydroxybenzylidene)hydrazine‐1‐carboxamide (DHHC) and its water assisted photoinduced tautomerization. DHHC is feebly emissive in non‐polar solvents but the fluorescence intensity intensifies (at 406 nm) in alcohols possibly due to intermolecular H‐bonding. However, in protic polar water, the scenario is markedly different, the fluorescence intensity decreases a bit as compared to alcohols and the emission maxima shifted from 406 nm to 430 nm probably due to solvent (water) assisted excited state proton transfer reaction (ESPT). In contrast to the reported excited state intramolecular proton transfer reaction (ESIPT) in various compounds, DHHC on photoexcitation loses a proton from its phenolic ‐OH group to the water molecule, which insists a subsequent proton transfer from the hydronium ion to the imine nitrogen of DHHC resulting 24 nm red‐shifted fluorescence emission from the tautomeric species of DHHC, in aqueous media. The mechanism of ESPT reaction is explained theoretically through the reaction kinetics of the DHHC‐water complex (in ratio 1 : 3) in an explicit CPCM solvent model. The illustration of the findings may open up enormous possibilities for Semicarbazone Schiff bases to be used as a probe for water sensing inside biomacromolecules like proteins and enzymes.

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Exploration of the ESIPT process in a newly designed potential bioactive thiosemicarbazone Schiff base: Spectroscopic analysis accompanied by molecular optimization and crystallographic study

Cited by 16 publications

References 56 publications

Switching of the Polarity-Sensitive Aggregation Pattern of a Thiosemicarbazone-Based Anticancer Luminophore and Its Involvement in Cellular Apoptosis of the Human Lung Cancer Cell Line

Switching of the Polarity-Sensitive Aggregation Pattern of a Thiosemicarbazone-Based Anticancer Luminophore and Its Involvement in Cellular Apoptosis of the Human Lung Cancer Cell Line

Synthesis and Characterization of Acid-Responsive Luminescent Fe(II) Metallopolymers of Rigid and Flexible Backbone N-Donor Multidentate Conjugated Ligands

Water‐Assisted Photoinduced Tautomerization in a Potential Bioactive Semicarbazone Schiff Base

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