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Water-sensitive ratiometric fluorescent probes and application to test strip for rapid and reversible detection of water
摘要： Naphthalimide-decorated fluorinated acetamides 1 and 2 were developed as solvent-sensitive dual emissive fluorescence probes. Particularly, 1 exhibited dual emission with a large Stokes shift for water, DMF, and DMSO solvents over other various organic solvents. The dual emission might be due to the increase of intramolecular charge transfer (ICT) of the naphthalimide moiety through the association of the difluorinated acetamide group with the solvent molecules. The 1 can give rise to a ratiometric change in the dual emission and a visual fluorescent color change depending on the water contents in organic solvents, including ethanol, methanol, acetonitrile and DMF solvents. Moreover, the 1-impregnated paper strips showed a rapid and easy-to-visualize fluorescent color change enabling water detection in organic solvents. These simple-to-use paper strips were also found to be reusable over 20 times.
关键词： Naphthalimide,Ratiometric fluorescence probe,Reusable test strip,Intramolecular charge transfer (ICT),Water detection
更新于2025-11-19 16:46:39
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Mechanofluorochromism based on BOPIM complexes: The effect of substituents and regulation of the direction of the emission color changes
摘要： Novel boron 2-(2′-pyridyl)imidazole (BOPIM) complexes T1, T2 and T3 with different substituents (including bromo, tert-butyl and methoxyl) on the benzene ring of BOPIM dyes have been designed and synthesized, and their optical properties in both solution and the solid state were investigated and compared. The three compounds exhibited typical intramolecular charge transfer (ICT) characteristics. Solvent-dependent UV-vis absorption, fluorescence emission spectra and quantum chemical calculation indicated a molecular push-pull electronic structure. Their ICT degrees increased with the sequence of T1 < T2 < T3. The analysis of the X-ray crystal structure revealed the twisted molecular conformation of BOPIM dyes. Furthermore, they showed remarkable reversible mechanofluorochromic (MFC) features under mechanical force. It was found that the MFC activities could be tuned easily by changing the substituents on the BOPIM dyes. T1 exhibited emission color change from bright green to yellowish green with a spectral red-shift of only 22 nm under mechanical stimuli, whereas T2 and T3 gave the large spectral red-shifts of 36 and 30 nm. Electronic and steric effects of the substitutes were proved playing significant roles in regulating the ICT effect and intermolecular interactions. More importantly, the remarkable effect of substituents on the MFC behaviors of BOPIM dyes will provide an effective way to obtain novel high-contrast MFC dyes.
关键词： Mechanofluorochromism,Substituent effect,Intramolecular charge transfer,Solid-state fluorescence,BOPIM complexes
更新于2025-11-14 15:26:12
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Highly Selective Fluorescent Probe Based on 2-(2′-Dansylamidophenyl)-Thiazole for Sequential Sensing of Copper(II) and Iodide Ions
摘要： A novel highly selective fluorescent probe based on 2-(20-dansylamidophenyl)-4-phenylthiazole (1) is developed for sequential sensing of copper(II) and iodide ions in acetonitrile. The fluorescence mechanism is based on cation-induced inhibition of excited-state intramolecular hydrogen transfer, intramolecular charge transfer, and metal–ligand electron/charge transfer. Subsequent iodide-induced extrusion of copper(II) results in partial revival of fluorescence. Probe 1 and its ensemble with copper (II) show high selectivity for copper(II) and iodide ions, respectively, in acetonitrile solution.
关键词： Excited-state intramolecular hydrogen transfer,I?,Cu2+,Intramolecular charge transfer,Dansyl-thiazole conjugate
更新于2025-09-23 15:23:52
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Synthesis, characterization and photophysical properties of a new class of pyrene substituted 1,3,4-oxadiazole derivatives
摘要： We have designed and synthesized a series of a new class of pyrene substituted 1,3,4- oxadiazole derivatives (abbreviated as 3(a-e)) through palladium catalyzed Suzuki-Miyaura cross coupling reaction. The chemical structures of the probes were characterized by using analytical techniques namely 1H NMR, 13C NMR, FT-IR and GC-MS. The novel bipolar molecules consist of pyrene as an electron donor unit (D) and electron-deficient 1,3,4-oxadiazole as an acceptor unit (A) linked via extending π conjugation through a phenyl spacer with para linkages (D-π-A). Intramolecular charge transfer is improved by structure-property relationship. The detailed photophysical/solvatochromic properties of newly synthesized derivatives have been studied employing steady state spectroscopic techniques. The photophysical studies revealed that compounds emit strong indigo-blue fluorescence and efficient blue emission extending into blue-green in solid phase with high quantum yields. Thermal and morphological stabilities of the derivatives were studied employing DSC and TGA measurements. In addition, density functional theory (DFT) computations have been carried out to demonstrate various intramolecular interactions that cause the stabilization of the compound leading to its optoelectronic applications. The highest occupied molecular orbital energy (HOMOs), lowest unoccupied molecular orbital energy (LUMOs), the energy bandgap, chemical hardness (η), softness (δ), electronegativity (χ) and chemical potential (μ) were computed with the help of frontier molecular orbitals. The results were compared and discussed with the experimental results. The results demonstrate that the novel pyrene containing oxadiazole derivatives could be used as small organic molecules for multifunctional organic light-emitting devices (OLED)/optoelectronic devices.
关键词： Intramolecular charge transfer (ICT),1,3,4-Oxadiazole,Quantum yield,Pyrene,Density functional theory
更新于2025-09-23 15:23:52
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Ultrafast spectroscopy of the primary charge transfer and ISC processes in 9-anthraldehyde
摘要： The ultrafast charge transfer (CT) and the following intersystem crossing (ISC) processes of 9-anthraldehyde were investigated in ethanol and hexane using femtosecond transient absorption spectroscopy combined with quantum chemical calculations. The CT was observed within 0.11 ps in ethanol and 0.23 ps in hexane. Due to the stronger polarity in ethanol, the CT is faster than in hexane. The following ISC is determined to be 22.3 ps and 21.4 ps in two solvents, respectively. However, the timescales of ISC are similar in both solvents since the excited energies of the S1 and triplet states are close.
关键词： Time-resolved transient absorption spectroscopy,intramolecular charge transfer,radiationless intersystem crossing
更新于2025-09-23 15:23:52
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Effect of Planarity of Aromatic Rings Appended to o-Carborane on Photophysical Properties: A Series of o-Carboranyl Compounds Based on 2-Phenylpyridine- and 2-(Benzo[b]thiophen-2-yl)pyridine
摘要： Herein, we investigated the effect of ring planarity by fully characterizing four pyridine-based o-carboranyl compounds. o-Carborane was introduced to the C4 position of the pyridine rings of 2-phenylpyridine and 2-(benzo[b]thiophen-2-yl)pyridine (CB1 and CB2, respectively), and the compounds were subsequently borylated to obtain the corresponding C∧N-chelated compounds CB1B and CB2B. Single-crystal X-ray diffraction analysis of the molecular structures of CB2 and CB2B confirmed that o-carborane is appended to the aryl moiety. In photoluminescence experiments, CB2, but not CB1, showed an intense emission, assignable to intramolecular charge transfer (ICT) transition between the aryl and o-carborane moieties, in both solution and film states. On the other hand, in both solution and film states, CB1B and CB2B demonstrated a strong emission, originating from π-π * transition in the aryl groups, that tailed off to 650 nm owing to the ICT transition. All intramolecular electronic transitions in these o-carboranyl compounds were verified by theoretical calculations. These results distinctly suggest that the planarity of the aryl groups have a decisive effect on the efficiency of the radiative decay due to the ICT transition.
关键词： radiative decay,structural fluctuation,intramolecular charge transfer,o-carborane
更新于2025-09-23 15:22:29
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Versatile Phosphole Derivatives with Photovoltaic, Light-Emitting, and Resistive Memory Properties
摘要： A series of dithienophosphole compounds has been successfully synthesized and characterized by photophysical, electrochemical, and thermal studies. Possessing the electron-deficient dithienophosphole oxide moiety, these compounds are found to display strong intramolecular charge transfer character and exhibit high photoluminescence quantum yields of up to 0.68. Taking advantage of these phosphole-based the properties, compounds have been applied as active materials in the fabrication of organic photovoltaics (OPVs), organic light-emitting devices (OLEDs) and organic resistive memory devices. Satisfactory performances with power conversion efficiencies of up to 4.23% for OPV devices, external quantum efficiencies of up to 3.0% for OLEDs, and binary resistive memories with retention time of over 10000 s and distinctive OFF/ON current ratio of 1:107 have been realized based on these dithienophosphole compounds. These findings revealed the multifunctional behavior of these dithienophosphole compounds and represent for the first time the use of phosphole-based small molecules as donor materials for the vacuum-deposited OPV devices.
关键词： OPVs,dithienophosphole derivatives,multifunctional materials,resistive memory devices,fluorescent OLEDs,intramolecular charge transfer
更新于2025-09-23 15:19:57
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Lighting Up Invisible Twisted Intramolecular Charge Transfer State by High Pressure
摘要： The twisted intramolecular charge transfer (TICT) state plays an important role in determining the performance of optoelectronic devices. However, for some non-fluorescent TICT molecules, 'invisible' TICT state could only be visualized by modifying the molecular structure. Here, we introduce a new facile pressure-induced approach to light up the TICT state through the use of the pressure related liquid–solid phase transition of the surrounding solvent. Combining ultrafast spectroscopy and quantum chemical calculations, it reveals that the 'invisible' TICT state can emit fluorescence when the rotation of a donor group is restricted by the frozen acetonitrile solution. Furthermore, the TICT process can even be effectively regulated by the external pressure. Our study offers a unique strategy to achieve dual fluorescence behavior in charge transfer molecules and is of significance for optoelectronic and biomedical applications.
关键词： Dual fluorescence,Twisted intramolecular charge transfer,High pressure,Ultrafast spectroscopy
更新于2025-09-19 17:15:36
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Diarylpyrazine-based position isomers: A detailed study of optical properties and structure-property relationship
摘要： A versatile and expeditious synthetic route to pyrazine-based symmetric and asymmetric chromophores decorated with donor-acceptor (D-A) has been designed to study their structural effects on optical properties. Suzuki-Miyaura coupling of dihalopyrazine with various aryl boronic acids was synthesized under microwave condition. Pyrazine functionalized at C-2, C-5 and C-6 serve as acceptor to construct linear and angular push-pull chromophores. The photophysical, electrochemical and thermal properties of all the target chromophores were systematically investigated and the results were correlated theoretically by density functional theory computations. The emission wavelength was significantly red-shifted by introduction of strong electron withdrawing group (CN). The permutation of terminal donor acceptor units tunes the optoelectronic properties in a predictable way, aiding in the rational design of small molecule for luminescent materials. These chromophores displayed multicolor change in different solvents, exhibiting good solvatochromism with a large Stokes shift.
关键词： solvatochromism.,cross-coupling,Diarylpyrazine,intramolecular charge transfer
更新于2025-09-19 17:13:59
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Solvation Controlled Excited-State Planarization in a Pusha??Pull Pyrene Dye
摘要： The excited state deactivation pathway of the push–pull pyrene derivative (EPP), a molecule emitting bright red fluorescence, has been studied in several solvents using quantum chemical calculations, femtosecond time-resolved fluorescence up-conversion spectroscopy and femtosecond transient absorption spectra (fs-TA). From the steady-state spectra, EPP has shown a strong negatively solvatochromic behavior of the absorption spectra and a non-solvatochromic emission spectra, revealing the decreased dipole moment upon excitation. Femtosecond up-conversion measurements have shown interesting rise-decay kinetics at red emission side and fs-TA spectra also feature the SE (Stimulated emission) formed and new ESA (Excited State Absorption) developed in all investigated solvents. The careful analysis of the data gathered from fluorescence up-conversion and fs-TA spectra, supported by DFT quantum chemical calculations and temperature-dependent fluorescence measurements, unambiguously pointed out the excited state relaxation pathway of EPP is controlled by solvent stabilized planar intramolecular charge transfer (PICT) dynamics. This finding confirms the surrounding solvents as a significant factor that affects the rate of excited state conformation changes.
关键词： solvation controlled,push–pull pyrene derivative,excited state deactivation,planar intramolecular charge transfer,femtosecond spectroscopy
更新于2025-09-19 17:13:59