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A new multi-analyte fluorogenic sensor for efficient detection of Al <sup>3+</sup> and Zn <sup>2+</sup> ions based on ESIPT and CHEF features
摘要： The fluorogenic chemosensor 3-(((2-hydroxy-4-methylphenyl)imino)methyl)-[1,10-biphenyl]-4-ol (H2L) efficiently detects Zn2+ and Al3+ ions and subsequently fluoride ion in methanol–water (4/1, v/v, pH = 7.2) solution. The probe itself is non-emissive but upon treatment with Al3+ and Zn2+, it exhibits high fluorescence emission at two different wavelengths of 546 nm and 529 nm, respectively. Both excited-state intramolecular proton transfer (ESIPT) and chelation enhanced fluorescence (CHEF) processes play important roles in the enhancement of fluorescence intensity. Chelation of Zn2+ and Al3+ with the probe (H2L) inhibits CQN isomerization and ESIPT which consequently enhances the emission intensity. The emission intensity of H2L–Al3+ is selectively quenched upon titration with F- anions. The structure of the probe is confirmed by the single crystal X-ray diffraction method. The electronic structure and sensing mechanism of the probe (H2L) are supported by density functional theory (DFT) and time-dependent density functional theory (TDDFT).
关键词： Zn2+ detection,fluoride detection,CHEF,fluorogenic sensor,ESIPT,Al3+ detection
更新于2025-11-19 16:46:39
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Theoretical elaboration about the excited state dynamical behaviors for a novel fluorescent sensor
摘要： Using the density functional theory (DFT) and time‐dependent density functional theory (TDDFT) methods, we theoretically explore a novel fluorescent sensor molecule (abbreviated as “2”) (Sensors Actuat B‐Chem. 2018, 263, 585). Because of its symmetry, three stable structures can be located, ie, 2‐enol, 2‐SPT, and 2‐DPT forms in both S0 and S1 states. Via comparing the bond lengths and bond angles involved in the hydrogen bonding moieties, we find the dual intramolecular hydrogen bonds should be strengthened in the S1 state. And based on infrared (IR) vibrational simulations, we further confirm the strengthening dual hydrogen bonds. Upon the photo‐excitation process, the charge redistribution via frontier molecular orbitals (MOs) reveals the tendency of excited state intramolecular proton transfer (ESIPT) reaction. In addition, the constructed S0‐state and S1‐state potential energy curves demonstrate that the excited state single proton transfer (ESSPT) should be the most supported one from 2‐enol to 2‐SPT form. In view of the S1‐state stable 2‐SPT and 2‐DPT structures as well as the fluorescence peaks of them, we can further confirm the ESSPT mechanism for 2 chemosensor. This work not only clarifies the excited state behaviors of 2 system but also successfully explain the previous experimental phenomenon.
关键词： charge redistribution,ESIPT,potential energy curves,intramolecular hydrogen bond
更新于2025-09-23 15:23:52
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Synthesis and fluorescence studies of selected N-aryl-2-aminoquinolines: Effect of hydrogen bonding, substituents and ESIPT on their fluorescence quantum yields
摘要： N-aryl-2-aminoquinolines have been widely synthesised and used in biological applications. However, their luminescence properties have not been studied in detail. Herein a series of N-aryl-2-aminoquinolines was synthesised from substitution reaction between 2-chloroquinoline and anilines with different substituent groups gave sufficient yield from 72–90%. The fluorescence behaviour was investigated in toluene, ethyl acetate and ethanol. The result shows that fluorescence quantum yield of N-aryl-2-aminoquinolines was the highest in toluene, followed by in ethyl acetate and the lowest in ethanol. Quenched emission observed in ethanol is caused by site-specific fluorophore-solvent hydrogen bonding interactions, inducing deactivation of the quinolinyl ring system. The bell-shaped Hammett plot of various substituted compounds suggested that both strong electron donating and electron withdrawing groups caused significant quenching in the fluorescence quantum yields. Therefore, most types of substituent groups on the phenyl moiety, hydrogen bonding between the fluorophore and solvent, and excited-state intramolecular proton transfer (ESIPT) were found as crucial contributors to fluorescence quenching of N-aryl-2-aminoquinolines.
关键词： Substituent effects,ESIPT,Hydrogen bonding,N-aryl-2-aminoquinolines,Fluorescence quenching
更新于2025-09-23 15:23:52
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Fate of protected HBT based chemodosimeters after undergoing deprotection: Restoration of ESIPT or generation of emissive phenoxide?
摘要： -OH protected 2-(hydroxyphenyl) benzothiazole (HBT) based ratiometric chemodosimeters have previously been reported to undergo regeneration of excited state intramolecular proton transfer (ESIPT) process upon deprotection. In the current work it is demonstrated for the first time that generation of anion of HBT leads to the optical changes in these types of chemodosimeters rather than regeneration of HBT by using a Hydrazine specific chemodosimeter based on substituted HBT.
关键词： chemodosimeter,anion,HBT,ESIPT,ratiometric
更新于2025-09-23 15:23:52
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Two novel ESIPT benzothiazol derivatives and corresponding europium(Ⅲ) complexes: Synthesis and fluorescent properties
摘要： Two ESIPT benzothiazol derivatives and corresponding europium complexes were synthesized and characterized by the 1HNMR spectrum, Mass spectrum, Elemental analysis, UV–Vis analysis, Molar conductivity, Thermogravimetric analysis and FTIR analysis. The fluorescence intensity of the ligands and complexes are compared, and the fluorescence quantum yields are also calculated by the reference method. The results show that two ligands emit orange fluorescence due to the ESIPT process, but both complexes emit red fluorescence after coordinating with Eu3+. Compared with the ligands, the fluorescence intensity and fluorescence quantum yield of the complexes are enhanced, and the monochromaticity is also improved. Because of the stable tetradentate coordination, the fluorescence intensity of EuL7(NO3)3·2H2O is the strongest, and the order of fluorescence intensity is EuL7(NO3)3·2H2O > EuL6(NO3)3·2H2O > Ligand 6 > Ligand 7, so does the fluorescence quantum yields. The electrochemical properties of the complexes show that the HOMO energy level of EuL7(NO3)3·2H2O is higher than that of EuL6(NO3)3·2H2O, but LUMO energy level is lower than that of EuL6(NO3)3·2H2O. These ligands and complexes have potential applications in the field of life sciences and optical materials.
关键词： Electrochemical property,Benzothiazol derivative,Synthesis,ESIPT,Europium complex,Fluorescence property
更新于2025-09-23 15:22:29
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An ESIPT-based fluorescent probe for Hg2+ in aqueous solution and its application in live-cell imaging
摘要： A new Excited-State Intramolecular Proton Transfer (ESIPT) based fluorescent probe for the detection of Hg2+ has been rationally designed and developed. Based on the specific reactivity of mercury-promoted hydrolysis, the probe exhibits high selectivity and sensitivity for mercury ions in almost pure aqueous solution (containing only 1% DMSO) with a low detection limit of 1.9 ppb. Furthermore, the probe was also successfully used for fluorescence imaging of Hg2+ in live cells.
关键词： Fluorescent probe,ESIPT-based,Live-cell imaging,Mercury ions,3-Hydroxyphthalimide
更新于2025-09-23 15:22:29
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Excited-state intramolecular proton transfer-based multifunctional solid-state emitter: a fluorescent platform with ‘write-erase-write’ function
摘要： The excited-state intramolecular proton transfer (ESIPT)-based molecular probes have drawn significant attention owing to their environment-sensitive fluorescence properties, large Stokes shift and emerged as building blocks for the development of molecular sensors and switches. However, most of the ESIPT-based fluorophores exhibit weak emission in the solid state limiting the scope of real-time applications. Addressing such issues, herein, we presented a C3-symmetric like molecular architecture employing a simple one-step Schiff base condensation between triaminoguanidinium chloride and 3,5-di-tert-butyl-2-hydroxybenzaldehyde (TGHB). The temperature-dependent fluorescence studies including at 77 K indicated the strong emission from the keto tautomer compared to that of the enol. The facile ESIPT in TGHB in the solid-state led to a remarkable enhancement of fluorescence quantum yield of 1600-times compared to that of the solution (λem = 545 nm) by restricting the intramolecular rotation and subsequently suppressing the nonradiative deactivation. The excited–state processes were further elucidated through time-resolved fluorescence measurements. TGHB exhibited turn on-off fluorescence upon exposure to acid /base vapor in the form of powder as well as transparent, free-standing thin film. A rewritable and erasable fluorescent platform was demonstrated using TGHB as molecular ink, which offers a potential testbed for performing multiple times ‘write-erase-write’ cycles. In addition, TGHB, possessing multiple binding sites (O and N donors) involving the central core of triaminoguanidinium cation, displayed selective turn-on fluorescence with Zn2+. The structure-property relationship revealed in the present study provides insight towards the development of novel cost-effective multifunctional materials promising for stimuli-responsive molecular switches.
关键词： molecular ink,thin film,ESIPT,multifunctional,solid-state emission,fluorescence switching
更新于2025-09-23 15:21:21
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Investigation on the mechanism of ESIPT of 2-hydroxy-1-naphthaldehyde-(4-pyridinecarboxylic)- hydrazone and detection of Al<sup>3+</sup> ion
摘要： The sensing mechanism of 2-hydroxy-1-naphthaldehyde-(4-pyridinecarboxylic)-hydrazone for Al3+ is investigated based on the excited-state intramolecular proton transfer (ESIPT) and photo-induced electron transfer (PET) processes. Absorption and fluorescence spectra are calculated, which are well consistent with experimental results. By analyzing the major bond parameters, infrared (IR) vibrational spectra as well as frontier molecular orbitals (MOs), it can be concluded that the hydrogen bond is enhanced in the first singlet excited state (S1), which can also be visualized by the reduced density gradient function. Potential energy curves (PECs) are also scanned, which can elucidate that the ESIPT process is more likely to occur in the S1 state. Changes in molecular configuration and intensity of fluorescence emission confirmed that the ESIPT and PET processes are forbidden in the presence of Al3+.
关键词： ESIPT,Hydrogen bond,Reduced density gradient,Potential energy curve,Al3+ sensing
更新于2025-09-23 15:21:01
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Self-agglomerated crystalline needles harnessing ESIPT and AIEE features for the ‘turn-on’ fluorescence detection of Al <sup>3+</sup> ions
摘要： We report the synthesis of probe 2 for the fluorescence "turn-on" detection of Al3+ ions in CH3OH. Probe 2 has been designed via utilizing the aggregation-induced emission properties of the tetraphenylethylene unit, with further enhancement from Schiff base units for the ESIPT phenomenon. Probe 2 exhibits emission at 548 nm (lex = 360 nm), with a large Stokes shift of 188 nm, indicating the ESIPT phenomenon. Probe 2 also exhibits emission enhancement via increasing the H2O ratio up to 70–90% H2O/THF (v/v) and altering the spherical morphology to needle shapes. Probe 2 has been found to be highly selective and sensitive towards Al3+ ions over other metal ions in pure CH3OH using absorption and emission spectroscopy. FESEM analysis revealed that the size of probe 2 increases upon the addition of Al3+ ions. Thus, the fluorescence "turn-on" behaviour of probe 2(cid:2)Al3+ is due to metal-induced aggregation.
关键词： fluorescence detection,ESIPT,Al3+ ions,AIEE,aggregation-induced emission
更新于2025-09-19 17:15:36
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First-principles investigation of the double ESIPT process in a thiophene-based dye
摘要： The unusual emission spectrum of 2,5-bis(benzoxazol-2-yl)thiophene-3,4-diol (BBTP) is investigated. The complexity of the emission spectrum of this dye is due to the presence of two excited-state intramolecular proton transfer (ESIPT) sites that give rise to three non-equivalent tautomers. The different maxima were experimentally attributed to the initial double enol form, the single ESIPT enol–keto tautomer, and the double ESIPT structure. Our simulations, based on Time Dependent Density Functional Theory (TD-DFT) and post Hartree–Fock methods [ADC(2) and CC2] coupled to different schemes to include the solvent polarisation response, are able to reproduce the key experimental outcomes. Moreover, we prove that for solving the inconsistencies present in earlier theoretical studies, a state-specific solvation approach is needed: one should go beyond the standard linear-response scheme in polarisable dielectric models. Finally, using a validated model, we explore the impact of substitution by donor and acceptor groups.
关键词： TD-DFT,emission spectrum,BBTP,CC2,tautomers,ADC(2),ESIPT,solvent models
更新于2025-09-19 17:15:36