scholarly journals Excimeric Emission and Photochemical Behavior of p-Phenylenediacrylic Acid (p-PDA) and its Diethyl-Ester (p-PDAEt)

1985 ◽  
Vol 5 (5) ◽  
pp. 309-319 ◽  
Author(s):  
El-Zeiny M. Ebeid ◽  
Samy A. El-Daly ◽  
Masaki Hasegawa
Keyword(s):  
Diethyl Ester ◽  
Quantum Yields ◽  
Triplet States ◽  
Cetyltrimethylammonium Chloride ◽  
Concentrated Solutions ◽  
Molecular Emission ◽  
Fluorescence Quantum Yields ◽  
Emission Maximum ◽  
Cationic Micelles ◽  
Photoisomerization Process

p-Phenylenediacrylic acid (p-PDA) displays excimeric emission in concentrated solutions (concentration ca. 0.5 M) in dimethylsulphoxide (DMSO). The excimeric emission maximum is red shifted by ca. 5200 cm–1 compared with molecular emission maximum. The fluorescence quantum yields of p-PDA has been measured in DMSO (φf = 0.09, λex = 337 nm) and in cetyltrimethylammonium chloride (CTAC) cationic micelles that show remarkable solubilization of p-PDA.The solution photoreactivity of p-PDA is wavelength dependent. In dilute DMSO solutions, 365 nm and 310 nm light causes p-PDA consumption giving a photoproduct of maximum absorption at ca. 265 n,. A back photoreaction is induced by 254 nm light. The photochemical quantum yields (φc) of the forward photochemical reaction have been measured as a function of temperature and the activation energy was evaluated as Ea = 9 kJ mol–1 suggesting a unimolecular photoisomerization process.Emission from crystalline p-PDA has also been reported. The emission maximum is red shifted from molecular emission maximum by ca. 3250 cm–1.The energy transfer in the system diethyl-p-phenylenediacrylate (p-PDAEt)-1,4-bis(β-pyridyl-2-vinyl)benzene(P2VB) has been studied. Triplet states formation mechanism is proposed.

Properties of singlet- and triplet-excited states of hemicyanine dyes

2014 ◽  
Vol 68 (8) ◽  
Author(s):  
Daniel Mártire ◽  
Walter Massad ◽  
Hernán Montejano ◽  
Mónica Gonzalez ◽  
Paula Caregnato ◽  
...  
Keyword(s):  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Laser Flash ◽  
Quantum Yields ◽  
Triplet States ◽  
Fluorescence Emission Spectra ◽  
Fluorescence Quantum Yields ◽  
Hemicyanine Dyes

AbstractThe fluorescence emission spectra and fluorescence quantum yields of hemicyanine dyes LDS 698, LDS 722, and LDS 730 were measured in different media. No transient species was detected in the laser flash-photolysis experiments performed with Ar-saturated solutions of the dyes in methanol. However, in the presence of 0.08 M potassium iodide, the absorption of the triplet states was clearly observed. Oxygen consumption measurements in the absence and presence of a chemical trap (furfuryl alcohol) in MeOH: H2O (φ r = 1: 1) solutions of the dyes containing KI confirmed the generation of singlet molecular oxygen.

scholarly journals Emission Quenching in Tetraphenylfuran Crystal: Why This Propeller-Shaped Molecule Does Not Emit in the Condensed Phase?

Molecules ◽  
2022 ◽  
Vol 27 (2) ◽  
pp. 522
Author(s):  
Ljiljana Stojanović ◽  
Rachel Crespo-Otero
Keyword(s):  
Solid State ◽  
Ground State ◽  
Light Emission ◽  
Quantum Yields ◽  
Triplet States ◽  
Fluorescence Quantum Yields ◽  
The Family ◽  
Emission Quenching ◽  
Significant Attention

Due to their substantial fluorescence quantum yields in the crystalline phase, propeller-shaped molecules have recently gained significant attention as potential emissive materials for optoelectronic applications. For the family of cyclopentadiene derivatives, light-emission is highly dependent on the nature of heteroatomic substitutions. In this paper, we investigate excited state relaxation pathways in the tetraphenyl-furan molecule (TPF), which in contrast with other molecules in the family, shows emission quenching in the solid-state. For the singlet manifold, our calculations show nonradiative pathways associated with C-O elongation are blocked in both vacuum and the solid state. A fraction of the population can be transferred to the triplet manifold and, subsequently, to the ground state in both phases. This process is expected to be relatively slow due to the small spin-orbit couplings between the relevant singlet-triplet states. Emission quenching in crystalline TPF seems to be in line with more efficient exciton hopping rates. Our simulations help clarify the role of conical intersections, population of the triplet states and crystalline structure in the emissive response of propeller-shaped molecules.

scholarly journals Arylisoquinoline-derived organoboron dyes with a triaryl skeleton show dual fluorescence

2019 ◽  
Vol 15 ◽  
pp. 2612-2622
Author(s):  
Vânia F Pais ◽  
Tristan Neumann ◽  
Ignacio Vayá ◽  
M Consuelo Jiménez ◽  
Abel Ros ◽  
...  
Keyword(s):  
Emission Band ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Quantum Yields ◽  
Triplet States ◽  
Dual Emission ◽  
Long Wavelength ◽  
Fluorescence Quantum Yields ◽  
Wavelength Emission

Four new dyes that derive from borylated arylisoquinolines were prepared, containing a third aryl residue (naphthyl, 4-methoxynaphthyl, pyrenyl or anthryl) that is linked via an additional stereogenic axis. The triaryl cores were synthesized by Suzuki couplings and then transformed into boronic acid esters by employing an Ir(I)-catalyzed reaction. The chromophores show dual emission behavior, where the long-wavelength emission band can reach maxima close to 600 nm in polar solvents. The fluorescence quantum yields of the dyes are generally in the range of 0.2–0.4, reaching in some cases values as high as 0.5–0.6. Laser-flash photolysis provided evidence for the existence of excited triplet states. The dyes form fluoroboronate complexes with fluoride anions, leading to the observation of the quenching of the long-wavelength emission band and ratiometric response by the build-up of a hypsochromically shifted emission signal.

Fluorescence quantum yields of dye aggregates: a showcase example based on self-assembled perylene bisimide dimers

2018 ◽  
Vol 20 (11) ◽  
pp. 7612-7620 ◽  
Author(s):  
Franziska Fennel ◽  
Jana Gershberg ◽  
Matthias Stolte ◽  
Frank Würthner
Keyword(s):  
Quantum Yield ◽  
Quantum Yields ◽  
Concentrated Solutions ◽  
Perylene Bisimide ◽  
Fluorescence Quantum Yields ◽  
Yield Determination ◽  
Self Assembled ◽  
Supramolecular Aggregates

Two measurement approaches for the precise quantum yield determination of supramolecular aggregates in highly concentrated solutions are presented and experimentally tested for an emissive perylene bisimide H-type aggregate with a quantum yield of 28%.

Regioselective Oxidative Cross-Coupling Reaction: Synthesis of Imidazo[1,2-a]pyridine Fluorophores

Synthesis ◽  
2021 ◽  
Author(s):  
Xianglong Chu ◽  
Yadi Niu ◽  
Chen Ma ◽  
Xiaodong Wang ◽  
Yunliang Lin ◽  
...  
Keyword(s):  
Photophysical Properties ◽  
Coupling Reaction ◽  
Cross Coupling ◽  
Quantum Yields ◽  
Fluorescence Quantum Yields ◽  
Cross Coupling Reaction ◽  
Color Tunable ◽  
Palladium Catalyzed ◽  
Structure Relationship ◽  
High Fluorescence

AbstractA rapid access to a series of N-heteroarene fluorophores has been developed on the basis of the palladium-catalyzed direct oxidative C–H/C–H coupling of imidazo[1,2-a]pyridines with thiophenes/furans. The photophysical properties–structure relationship was systematically investigated. The resulting N-heteroarene fluorophores present color-tunable emissions (λem: 431–507 nm in CH2Cl2) and high fluorescence quantum yields (up to 91% in CH2Cl2).

scholarly journals Indenopyrans – synthesis and photoluminescence properties

2016 ◽  
Vol 12 ◽  
pp. 825-834 ◽  
Author(s):  
Andreea Petronela Diac ◽  
Ana-Maria Ţepeş ◽  
Albert Soran ◽  
Ion Grosu ◽  
Anamaria Terec ◽  
...  
Keyword(s):  
Solid State ◽  
Emission Band ◽  
Fluorescence Spectra ◽  
Photophysical Properties ◽  
Quantum Yields ◽  
Band Broadening ◽  
Photoluminescence Properties ◽  
Fluorescence Quantum Yields ◽  
Blue Emitters ◽  
Solid State Fluorescence

New indeno[1,2-c]pyran-3-ones bearing different substituents at the pyran moiety were synthesized and their photophysical properties were investigated. In solution all compounds were found to be blue emitters and the trans isomers exhibited significantly higher fluorescence quantum yields (relative to 9,10-diphenylanthracene) as compared to the corresponding cis isomers. The solid-state fluorescence spectra revealed an important red shift of λmax due to intermolecular interactions in the lattice, along with an emission-band broadening, as compared to the solution fluorescence spectra.

Mechanistic studies of aromatic ketone-sensitized photoreduction of bis(acetylacetonato)copper(II)

1983 ◽  
Vol 61 (5) ◽  
pp. 801-808 ◽  
Author(s):  
Yuan L. Chow ◽  
Gonzalo E. Buono-Core ◽  
Bronislaw Marciniak ◽  
Carol Beddard
Keyword(s):  
Rate Constant ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Decay Rates ◽  
Polynuclear Aromatic Hydrocarbons ◽  
Aromatic Ketone ◽  
Quantum Yields ◽  
Triplet States ◽  
Quenching Rate ◽  
Triplet Energy

Bis(acetylacetonato)copper(II), Cu(acac)2, quenches triplet excited states of ketones and polynuclear aromatic hydrocarbons efficiently, but only aromatic ketones with high triplet energy successfully sensitize photoreduction of Cu(acac)2 in alcohols under nitrogen to give derivatives of aeetylacetonatocopper(I), Cu(acac). For the triplet state benzophenone-sensitized photoreduction of Cu(acac)2, the quantum yields of photoreduction (ΦC) and those of benzophenone disappearance (ΦB) were determined in methanol with various concentrations of Cu(acac)2. The values of the quenching rate constant, kq, determined from these two types of monitors on the basis of the proposed mechanism were in good agreement (6.89 ~ 7.35 × 109 M−1 s−1). This value was higher, by a factor of about two, than that obtained from the monitor of the benzophenone triplet decay rates generated by flash photolysis in the presence of Cu(acac)2. The quenching rate constants of various aromatic ketone and hydrocarbon triplet states by Cu(acac)2 were determined by flash photolysis to be in the order of the diffusion rate constant and the quantum yields of these photoreductions were found to be far from unity. Paramagnetic quenching, with contributions of electron exchange and charge transfer, was proposed as a possible quenching mechanism. For a series of aromatic ketone sensitizers with higher triplet energy, this mechanism was used to rationalize the observed high quenching rate constants in contrast to the low quantum yields of photoreduction.

Impact of cyclic topology: odd–even glass transition temperatures and fluorescence quantum yields in molecularly-defined macrocycles

2017 ◽  
Vol 8 (17) ◽  
pp. 2686-2692 ◽  
Author(s):  
Kun Li ◽  
Ganquan Jiang ◽  
Feng Zhou ◽  
Lishan Li ◽  
Zhengbiao Zhang ◽  
...  
Keyword(s):  
Glass Transition ◽  
Intermolecular Interactions ◽  
Topological Structure ◽  
Quantum Yields ◽  
Transition Temperatures ◽  
Glass Transition Temperatures ◽  
Fluorescence Quantum Yields

The topological structure of cyclic-TPEn+1 (n = 1–6) induces odd–even effects on the Tg and AIE behavior, arising from the alternation of intermolecular interactions.

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