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Long-lived triplet excited state in a platinum( <scp>ii</scp> ) perylene monoimide complex
摘要： We report the synthesis and solution based photophysical properties of a new Pt(II)-terpyridine complex coupled to a perylene monoimide (PMI) chromophoric unit through an acetylene linkage. This structural arrangement resulted in quantitative quenching of the highly fluorescent PMI chromophore by introducing metal character into the lowest energy singlet state, thereby leading to the formation of a long-lived PMI-ligand localized triplet excited state (τ = 8.4 μs). Even though the phosphorescence from this triplet state was not observed, highly efficient quenching of this excited state by dissolved oxygen and the observation of singlet oxygen photoluminescence in the near-IR at 1270 nm initially pointed towards triplet excited state character. Additionally, the coincidence of the excited state absorbance difference spectra from the sensitized PMI ligand using a triplet donor and the Pt-PMI complex provided strong evidence for this triplet state assignment, which was further supported by TD-DFT calculations.
关键词： singlet oxygen,perylene monoimide,photophysics,platinum(II) complex,triplet excited state
更新于2025-11-19 16:56:42
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Control of Excited-State Supramolecular Assembly Leading to Halide Photorelease
摘要： Ground- and excited-state control of halide supramolecular assembly was achieved through the preparation of a series of ester- and amide-functionalized ruthenium polypyridyl complexes in CH2Cl2. Hydrogen-bonding amide and alcohol groups on the receptor ligand were found to direct interactions with halide, while halide association with the ethyl ester groups was not observed. The various functional groups on the receptor ligands tuned the ground-state equilibrium constants over 2 orders of magnitude (1 × 10^5 to 1 × 10^7 M^?1), and the fractional contribution of each hydrogen-bond donor to the total equilibrium constant was determined. Pulsed-laser excitation of the complexes resulted in excited-state localization on the ester- or amide-functionalized ligands. In the case where the excited state was oriented toward an associated halide ion (the amide complexes), an 80 ± 10 meV Coulombic repulsion was induced that lowered the excited-state equilibrium constant (K*_eq) and resulted in halide photorelease. The rate constants for excited-state halide release (k*_21) were determined, and the values varied based on the functional groups present in the receptor ligand. Complexes with more hydrogen-bonding donors had smaller rate constants for halide photorelease. In a complex without a specific receptor ligand, the excited-state dipole was not oriented toward the associated halide, and the excited state was therefore found to have a larger equilibrium constant for halide association than the ground state.
关键词： halide supramolecular assembly,excited-state equilibrium,photorelease,hydrogen-bonding,ruthenium polypyridyl complexes
更新于2025-11-19 16:56:35
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Excited state intramolecular single proton transfer mechanism of pigment yellow 101 in solid state: Experiment and DFT calculation
摘要： To investigate fluorescence mechanism of Pigment Yellow 101 (P. Y. 101) in solid state, three aromatic aldehyde azines (1-3) including P. Y. 101 have been synthesized and compared with each other. Results indicated that P. Y. 101 prepared by solvothermal method is actually the mixture of two polymorphs, whose molecular packing mode can be transformed into each other by recrystallizing or external stimuli such as pressure and grinding. The ESIPT properties of 1-3 were investigated by DFT/TD-DFT calculations and time-correlated single photon counting (TCSPC) technique. Both experimental and theoretical results revealed that the dual fluorescence properties of P. Y. 101 in solid state are ascribed to the excited-state intramolecular single proton transfer fluorescence emissions of two structurally different polymorphs rather than the results of the sequential or concerted excited-state intramolecular double proton transfers, which provide a potential valuable tool for developing multistimuli-responsive luminescent materials.
关键词： Aromatic aldehyde azines,DFT calculation,P. Y. 101,Excited-state intramolecular proton transfer,Polymorphs
更新于2025-11-19 16:56:35
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Competing photochemical reactions of bis-naphthols and their photoinduced antiproliferative activity
摘要： Photophysical properties and photochemical reactivity for a series of bis-naphthols 4a-4e and bis-anthrols 5a and 5e were investigated by preparative irradiations in CH3OH, fluorescence spectroscopy and laser flash photolysis (LFP). Methanolysis taking place via photodehydration (bis-naphthols ΦR = 0.04-0.05) is in competition with symmetry breaking charge separation (SB-CS). The SB-CS gives rise to radical ions that were for 4a and 4e detected by LFP. Photodehydration gives quinone methides (QMs) that were also detected by LFP (λmax = 350 nm, τ ≈ 1-2 ms). In the aqueous solvent, excited state proton transfer (ESPT) competes with the above mentioned processes, giving rise to naphtholates, but the process is inefficient and can only be observed in the buffered aqueous solution at pH >7. Since the dehydration of bis-naphthols delivers QMs, their potential antiproliferative activity was investigated by MTT test on three human cancer cell lines (NCI-H1299, lung carcinoma; MCF-7, breast adenocarcinoma; and SUM159, pleomorphic breast carcinoma). Cells were treated with 4 or 5 with or without irradiation (350 nm). An enhancement of the activity (up to 10-fold) was observed upon irradiation, which may be associated to the QM formation. However, these QMs do not cross-link DNA. The activity is most likely associated to the alkylation of proteins present in the cell cytoplasm, as evidenced by photoinduced alkylation of bovine and human serum albumins by 4a.
关键词： quinone methides,bis-anthrols,excited state proton transfer,protein alkylation,bis-naphthols,antiproliferative activity,photodehydration,symmetry breaking charge separation
更新于2025-11-14 15:32:45
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Excited State Dynamics of [Ru(bpy)3]2+ Thin Films on Sensitized TiO2 and ZrO2
摘要： The excited state dynamics of Tris(2,2'-bipyridine)ruthenium(II) hexafluorophosphate, [Ru(bpy)3(PF6)2], was investigated on the surface of bare and sensitized TiO2 and ZrO2 films. The organic dyes LEG4 and MKA253 were selected as sensitizers. A Stern-Volmer plot of LEG4-sensitized TiO2 substrates with a spin-coated [Ru(bpy)3(PF6)2] layer on top shows considerable quenching of the emission of the latter. Time-resolved emission spectroscopy interestingly reveals the presence of a fast-decay time component (25±5 ns), which is absent when the anatase TiO2 semiconductor is replaced by ZrO2. It should be specified that the positive redox potential of the ruthenium complex prevents electron transfer from the [Ru(bpy)3(PF6)2] ground state into the oxidized sensitizer. Therefore, we speculate that the fast-decaying time component observed may be identified with excited-state electron transfer from [Ru(bpy)3(PF6)2] to the oxidized sensitizer. Solid-state dye sensitized solar cells (ssDSSCs) employing MKA253 and LEG4 dyes, with [Ru(bpy)3(PF6)2] employed as a hole-transporting material (HTM), exhibit 1.2% and 1.1% power conversion efficiency, respectively. This result illustrates the possibility of the hypothesized excited-state electron transfer.
关键词： Photochemistry,Excited-state electron transfer,DSSCs,Ru(bpy)3,Solid state
更新于2025-09-23 15:23:52
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Enhancing Reverse Intersystem Crossing via Secondary Acceptors: towards Sky-Blue Fluorescent Diodes with Tenfold-Improved Exter-nal Quantum Efficiency
摘要： How to simply but effectively facilitate reverse intersystem crossing (RISC) transition is always the key issue for developing high-performance thermally activated delayed fluorescence (TADF) dyes. In this work, as a proof of concept, a feasible strategy named 'acceptor enhancement' is demonstrated with a series of ternary blue emitters (xCzmPOnTPTZ) using diphenylphosphine oxide (PO) as secondary acceptors. Compared with its PO-free binary analogue, such simple introduction of PO groups in pCzPO2TPTZ dramatically enhances its RISC rate constant (kRISC) by 10 times to the level of ~105 s-1, accompanied by RISC efficiency (ηRISC) of 92%, which further improves the triplet-to-singlet upconversion for effective triplet harvesting in its devices. As the result, on the basis of a trilayer device structure, pCzPO2TPTZ realized a state-of-the-art external quantum efficiency (EQE) beyond 20% with tenfold improvement.
关键词： Organic Light-Emitting Diode,Thermally Activated Delayed Fluorescence,Excited State Transition,Blue Emission,Reverse Intersystem Crossing,Phosphine Oxide Acceptor
更新于2025-09-23 15:23:52
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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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SwissKnife-Inspired Multifunctional Fluorescence Probes for Cellular Organelle Targeting Based on Simple AIEgens
摘要： Facile, efficient and mass production of aggregation-induced emission (AIE) luminogens (AIEgens) with excited-state intramolecular proton transfer (ESIPT) characteristics was achieved by one-step condensation reaction of 2-(hydrazonomethyl)phenol with benzaldehydes. The function of as-prepared AIEgens could be tuned easily by varying the functional group carrying on the phenyl ring of benzaldehyde just like Swiss knife handle. The suitable distance and angle of intramolecular hydrogen bond in these AIEgens endowed them with ESIPT properties, intense solid-state luminescence and large Stokes shifts (155?169 nm). These AIEgens could not only serve as biological probes showing specific targeting to lipid droplets, endoplasmic reticulum and lysosomes, respectively, but also generate reactive oxygen species upon visible light irradiation to make them promise for photodynamic therapy.
关键词： Fluorescence probes,Aggregation-induced emission,Excited-state intramolecular proton transfer,Photodynamic therapy,Organelle-targeting
更新于2025-09-23 15:23:52
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Spectroscopic behavior, FMO, NLO and NBO analysis of two novel aryl boronic acid derivatives: Experimental and theoretical insights
摘要： Here we report, experimental and theoretical determination of ground and excited state dipole moments of aryl boronic acid derivatives, 2-Bromophenyl boronic acid (2BPBA) and 2-Isopropylphenyl boronic acid (2IPBA). In both the compounds, Bathochromicshift is observed with increasing solvent polarity indicating π →π* transition due to intermolecular charge transfer interactions. For both the compounds, the ground and excited sate dipole moments are parallel to each other. The excited state dipole moment (μe) is greater than ground state dipole moment (μg) for the compound 2IPBA where as for 2BPBA, excited state dipole moment (μe) is less than ground state dipole moment (μg). Further, experimentally obtained Δμ are compared with those using microscopic empirical solvent polarity (??????). In parallel, the use of Kamlet-Taft parameters to the solvent effect on spectral properties of 2BPBA and 2IPBA are also discussed. The molecular structure, Frontier Molecular Orbitals (FMO), Natural Bond Orbital (NBO) analysis, Non-Linear Optical (NLO) properties of 2BPBA and 2IPBA have been investigated using the (DFT) calculations with B3LYP/6?311++G (d, p) basis set. The chemical reactivity and kinetic stability of the compounds is shown by differences between the energy levels by analyses of Frontier molecular orbitals. The polarizability and hyperpolarizability computations determine the NLO properties, whereas Natural bond orbital (NBO) analysis showed proton transfer within the selected donor-acceptor depicting large energy of stabilization for the compounds under study.
关键词： Kamlet-Taft,FMO,MEP,ground and excited state dipole moments,Solvatochromic shift method,NBO and NLO
更新于2025-09-23 15:23:52
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Tuning the Spectrum Properties of Fullerene C60: Using a Strong External Electric Field
摘要： The electric ?eld can change the absorption of fullerene C60 to different wavelengths of light by affecting the vibrational modes and electronic transitions. The IR spectrum of fullerene C60 under the strong electric ?eld is studied on B3LYP/6-31G* basis set using density function theory. With the external electric ?eld decreasing, silent modes Hg(1), Ag(1), Gu(2), Hg(5), Ag(2), Hu(7) become active. Meanwhile, UV–Vis spectrum, the excitation energy, excitation wavelength and oscillator strength of ?rst fourteen excited states of fullerene C60 under the ?eld are also studied in B3LYP/6-31G* basis set using time-dependent density functional theory. With the electric ?eld increasing, the absorption peak of fullerene C60 occurs then shifts towards the long-wave region. The excitation energy decrease and the excitation wavelength increase correspondingly, and external electric ?eld makes fullerene C60 absorb energy from 1.01 to 2.31 eV in theory. The energy gap decreases drastically from 2.74 to 1.38 eV, which contributed to tune the energy gap of fullerene C60 by the effect of the electric ?eld in a wide range. It is possible to use electric ?eld to tune fullerene C60 into new energy storage material.
关键词： External electric ?eld,Excited state,Cluster,IR spectrum,Fullerene C60
更新于2025-09-23 15:23:52