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Cascade recognition of Hg <sup>2+</sup> and cysteine using a naphthalene based ESIPT sensor and its application in a set/reset memorized device
摘要： An optical ESIPT sensor for Hg2+ and cysteine based on a naphthalene platform (1) was designed and synthesized by a one step reaction and characterized by using common spectroscopic techniques. Upon addition of Hg2+ to a 9 : 1 (v/v) aqueous CH3CN (pH 7.0 HEPES buffer) solution of 1, the highly fluorescent probe becomes weakly fluorescent, showing a color change from colorless to dark yellow visible to the naked eye and from fluorescent blue to light yellow when irradiated with 365 nm light. The sensing mechanism has been supported by DFT and 1H NMR titration studies. The in situ generated 1–Hg2+ complex has been used for effectively sensing Cys. Owing to the stronger binding affinity of the sulfhydryl group to Hg2+, Cys can extract Hg2+ from the 1–Hg2+ complex, resulting in the release of 1 and revival of the emission intensity. Sensor 1 has also been successfully applied for the detection of Hg2+ in real water samples with good recovery. The alternate addition of Hg2+ and Cys ions generated "on–off–on" fluorescence cycles, which enabled 1 to be used as a reversible and reconfigurable set/reset memorized device at the molecular level.
关键词： molecular logic device,fluorescence,Hg2+ detection,cysteine sensing,ESIPT sensor
更新于2025-09-19 17:15:36
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A new turn-on fluorescent probe with ultra-large fluorescence enhancement for detection of hydrogen polysulfides based on dual quenching strategy
摘要： Based on dual quenching strategy (ESIPT inhibited quenching and PET quenching), we have developed a new turn-on fluorescent probe 1. Combining 3-(benzo[d]thiazol-2-yl)-10-butyl-10H-phenothiazin-2-ol (dye 2) as the fluorophore and 2-fluoro-5-nitro-benzoic as the recognition moiety, probe 1 had feature of notable large Stokes shift, highly sensitivity and selective for monitoring H2Sn with remarkable fluorescence enhancement (328-fold) response at 534 nm. Probe 1 exhibited excellent performance in the quantitative detection of H2Sn with a 137 nm Stokes shift and a low detection limit of 26 nM in solution. Finally, probe 1 was successfully utilized to image H2Sn in living A549 cells and zebrafish.
关键词： Large stokes shift,ESIPT,Hydrogen polysulfides,PET
更新于2025-09-19 17:15:36
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Pyridine-hydrazone-controlled cyanide detection in aqueous media and solid-state: tuning the excited-state intramolecular proton transfer (ESIPT) fluorescence modulated by intramolecular NH?Br hydrogen bonding
摘要： A new efficient pyridine-hydrazone-substituted naphthalimide receptor 4a-E has been synthesized as a selective colorimetric and fluorescent chemosensor for cyanide sensing in aqueous environments through a unique excited-state intramolecular proton transfer (ESIPT) mechanism. The addition of a Br group to the fluorophore skeleton at the ortho-position of hydrazone generates reference compounds (4b-E and 4c-Z). Interestingly, the potential intramolecular NH?Br hydrogen bonding might compete with the anion-induced intermolecular NH?A? hydrogen bonding, resulting in dramatic ESIPT suppression. The high emission of probe 4a-E and other control probes in solid-state is also investigated. Moreover, probe 4a-E preloaded on test papers, upon cyanide treatment, shows obvious changes in color which demonstrates that 4a-E is a writable platform. More importantly, it exhibits great potential application for the detection of cyanide in food materials and excellent performance in real-world water samples.
关键词： ESIPT,colorimetric,pyridine-hydrazone,fluorescent chemosensor,cyanide sensing
更新于2025-09-12 10:27:22
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Benzothiazole pyrazole containing emissive azo dyes decorated with ESIPT core: Linear and non linear optical properties, Z scan, optical limiting, laser damage threshold with comparative DFT studies
摘要： Positional isomers of "benzothiazoles-pyrazole based azo dyes containing separate with ESIPT core" are analyzed for their "linear and non-linear optical (NLO)" properties. Dyes are emissive in ACN having Stokes shift in the range of 75 nm. Spectroscopic properties are further utilized to calculate band gap by CV. Band gap obtained by DFT and cyclic voltammetry (CV) are in good agreement with each other. Vertical excitation in six different functionals is compared with experimental absorption maxima. Non-linear absorptive coef?cient (b), nonlinear refractive index (?2), third-order non-linear optical suscep- tibility (c3) and optical limiting (OL) in acetone, ethanol and DMSO are obtained using Z-scan technique and results are appreciable than previously reported dyes. Satisfactory laser damage threshold (LDT) values are in the range of 7.9e9.7 (cid:1) 1013 W/m2. TGA study indicates that these compounds are useful in several high-temperature processes in the construction of electronic and optical devices. The geometry of the dyes are optimized at "B3LYP/6-311 t G (d,p) level". "Molecular Electrostatic Potential" (MEP), "Frontier Molecular Orbitals" (FMO) are presented using "Density Functional Theory (DFT)" to gain structural insights. Relatively new electrophilicity descriptor- "Hyperhardness" for both the molecules are calculated which suggests the stability of molecules. Global hybrid (GH) functional (B3LYP, BHandHLYP) and range separated hybrid (RSH) (CAM-B3LYP, uB97, uB97X, and uB97XD) functional are used to calculate linear and NLO properties. uB97 is a more suitable functional observed for determining bo and g. Direct relation in-between "dipole moment" (m) and "linear polarizability" (a) is also presented. These dyes can emerge as attractive NLOphores in optoelectronic applications.
关键词： ESIPT,NLO,Z-scan,LDT,DFT,Emissive azo dyes,Benzothiazole-pyrazole
更新于2025-09-11 14:15:04
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Proton-transfer based azides with fluorescence off–on response for detection of hydrogen sulfide. An experimental, theoretical and bioimaging study
摘要： This work describes the synthesis of photoactive proton transfer compounds based on the benzazolic core containing the azide group. The compounds present absorption in the UV region and fluorescence emission in the visible region of the spectra with large Stokes shift due to a phototautomerism in the excited state (ESIPT). The azide location on the benzazolic structure showed to present a noteworthy role on their photophysics leading to fluorescence quenching. A photophysical study was performed in the presence of NaHS to evaluate their application as H2S sensor. The methodology employed was the reduction of azides to amines using NaHS to mimic H2S, resulting in an off–on response fluorescence mechanism. The observed photophysical features were successfully used to explore the azides as fluorescent probes in biological media. In addition, DFT and TD-DFT calculations with CAM-B3LYP/cc-pVDZ and CAM-B3LYP/jun-cc-pVTZ level respectively were performed in order to understand the photophysics features of azide derivatives, where the main interest was investigate fluorescence quenching experimentally observed in the azide derivatives.
关键词： optical sensor,TD-DFT,fluorescence,ESIPT,azides
更新于2025-09-09 09:28:46
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Insights into the excited state dynamical process for 3-hydroxy-2-(5-(5-(5-(3-hydroxy-4-oxo-4H-chromen-2-yl)thiophen-2-yl)thiophen-2-yl)thiophen-2-yl)-4H-chromen-4-one
摘要： In this present work, we theoretically investigate a novel system 3‐hydroxy‐2‐(5‐(5‐(5‐(3‐hydroxy‐4‐oxo‐4H‐chromen‐2‐yl)thiophen‐2‐yl)thiophen‐2‐yl)thiophen‐2‐yl)‐4H‐chromen‐4‐one (FT) based on density functional theory (DFT) and time‐dependent DFT (TDDFT) methods. Via calculating the reduced density gradient (RDG) versus sign(λ2) ρ, we firstly verify the formation of the dual intramolecular hydrogen bonds (O1─H2···O3 and O4─H5···O6) for FT form in the S0 state. Then comparing the primary structural parameters and corresponding infrared (IR) vibrational spectra involved in hydrogen bonds between S0 and S1 state, we demonstrate that these two intramolecular hydrogen bonds should be strengthened in the S1 state. Insights into the vertical excitation process, our theoretical results reproduced experimental absorption nature, which confirms that the theoretical level (B3LYP/TZVP) is reasonable and effective in this work. And frontier molecular orbitals (MOs) depict the nature of electronically excited state and support the excited‐state intramolecular proton transfer (ESIPT) reaction. According to the calculated results of potential energy curves along stepwise and synergetic O1─H2 and O4─H5 coordinates, we verify that only the excited‐state single‐proton transfer could occur for FT molecule in the S1 state, although it possesses two intramolecular hydrogen bonds. We not only investigate the detail excited‐state behaviors for FT system and elaborate the ESIPT mechanism but also explain previous experimental results.
关键词： charge redistribution,ESIPT,intramolecular hydrogen bond,charge density difference
更新于2025-09-04 15:30:14
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Turning ESIPT-Based triazine fluorophores into dual emitters: From theory to experiment
摘要： In an effort to design new dyes presenting multiple fluorescence bands, we use theoretical chemistry to guide the synthesis of new triazine structures undergoing excited-state intramolecular proton transfer (ESIPT). Starting with experimentally-known compounds showing only emission from the keto tautomer, we model several chemically-achievable substitutions aiming to sufficiently frustrate the ESIPT process by stabilising the enol structure in the electronic excited state. In a second step, some of the proposed dyes are synthesised. It turns out that the emergence of an emission band due to the enol confirms the theoretical prediction, though the observed quantum yields in solution are small as a consequence of the selection of methoxy substituents. The quantum yields are strongly improved when going to the solid-state as a result of the impeded rotations.
关键词： dual emitters,theoretical chemistry,synthesis,triazine fluorophores,ESIPT
更新于2025-09-04 15:30:14
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Synthesis and Photophysical Characterization of Proton Transfer-Based Thiourea Derivatives: Potential Application as Colorimetric Naked-Eye Chemosensor for Fluoride Detection in Solution
摘要： Two new thiourea derivatives were synthesized through the reaction of photoactive aminohydroxybenzazoles and p-isothiocyanate benzoic acid via nucleophilic addition reaction. The compounds were characterized using high resolution mass spectrometry with eletrospray ionization (HRMS-ESI), Fourier transform infrared (FTIR), 13C and 1H nuclear magnetic resonance (NMR) spectroscopies. UV-Vis and steady-state fluorescence in solution were also applied to characterize their photophysical behavior. The compounds present absorption in the ultraviolet region (ca. 300 nm) and fluorescence emission with a large Stokes’ shift in the UV-A and green region, with the longer wavelength related to phototautomerism in the excited state (ESIPT). Both compounds were investigated as optical sensors for the detection of anions in solution, presenting a potential application for fluoride ion detection by naked-eye and UV-Vis spectroscopy. The continuous variation method plot gave a 1:1 stoichiometric ratio between the chemosensors and F– for the new formed species. The UV-Vis and 1H NMR titration experiments reflect the establishment of a hydrogen bond interaction between the thiourea moiety of the chemosensors and fluoride. In addition, the presence of fluoride in solution tailored the fluorescence emission of one compound favoring the ESIPT emission.
关键词： fluorescence,optical sensors,fluoride ion,ESIPT,benzazoles
更新于2025-09-04 15:30:14
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On the Fluorescent, Steric and Electronic Factors Affecting the Detection of Metallic Ions Using an Imidazolyl-Phenolic Derived Fluorescent Probe
摘要： The imidazolyl-phenolic probe used at the present study has its photophysic properties regulated by a tautomeric equilibrium. After the absorption of a photon, an excited state intramolecular proton transfer process generates a ketonic species, responsible for the 440 nm emission (in CH3CN/H2O, 95:5, v/v). Addition of Cu2+, Al3+, Cr3+ and Fe3+ suppresses emission through a combination of dynamic and static-like quenching, as indicated by Stern-Volmer plots, with a higher sensitivity for Cu2+ (KSV = 1.90 × 105 and 2.40 × 104 L mol–1, respectively, for Cu2+ and Fe3+). The trivalent ions led to the formation of a locked-enol tautomer that emits at shorter wavelengths; this coordinated compound is also quenched at metallic ions concentrations above 20 μmol L–1, due to a collisional process. When compared to another imidazolyl-phenolic probe, experimental and simulated data revealed that fluorescent, steric and electronic effects regulate their sensitivity towards the ions.
关键词： iron(III),copper(II),fluorescent sensor,ESIPT,tautomerization
更新于2025-09-04 15:30:14