Fluorescence and Phosphorescence of 2,3-Pentanedione

1972 ◽  
Vol 50 (9) ◽  
pp. 1331-1337 ◽  
Author(s):  
A. W. Jackson ◽  
A. J. Yarwood
Keyword(s):  
Quantum Yield ◽  
Triplet State ◽  
Temperature Variation ◽  
Delayed Fluorescence ◽  
Triplet States ◽  
Yield Data ◽  
System A ◽  
Singlet And Triplet States ◽  
Fluorescence And Phosphorescence

The fluorescence and phosphorescence yields on photolysis of 2,3-pentanedione were investigated at various temperatures. The processes involved in the formation and removal of both the singlet and triplet states are considered. The data agree qualitatively and quantitatively with the results of an earlier study of the lifetime of the triplet state. It is shown that delayed fluorescence is not observed in the pentanedione system. A mechanism is proposed that can correlate the temperature variation of both the lifetime and quantum yield data.

Emission and Deactivation of the Excited States of 2,3-Pentanedione

1972 ◽  
Vol 50 (9) ◽  
pp. 1338-1344 ◽  
Author(s):  
A. W. Jackson ◽  
A. J. Yarwood
Keyword(s):  
Triplet State ◽  
Gas Phase ◽  
Excited States ◽  
Singlet State ◽  
Triplet States ◽  
Excited Singlet ◽  
Vibrationally Excited ◽  
Singlet Level ◽  
Singlet And Triplet States ◽  
Fluorescence And Phosphorescence

Vibrationally excited singlet and triplet states of 2,3-pentanedione are formed by photolysis at 365 nm. The processes removing these excited states in the gas phase are studied by measuring the fluorescence and phosphorescence yields. Fluorescence can occur from the vibrationally excited, as well as the vibrationally equilibrated, singlet state. The fluorescence and phosphorescence data are considered in terms of mechanisms which involve either weak or strong collisions. Although the data cannot distinguish between the alternatives, there are two significant conclusions. The fluorescence data require that emission occur from at least two levels in the singlet manifold. To explain the phosphorescence data, the highest emitting singlet level must not lead to a vibrationally equilibrated triplet state.

scholarly journals P∩N Bridged Cu(I) Dimers Featuring Both TADF and Phosphorescence. From Overview towards Detailed Case Study of the Excited Singlet and Triplet States

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3415
Author(s):  
Thomas Hofbeck ◽  
Thomas A. Niehaus ◽  
Michel Fleck ◽  
Uwe Monkowius ◽  
Hartmut Yersin
Keyword(s):  
Quantum Yield ◽  
Decay Time ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Photo Luminescence ◽  
Delayed Fluorescence ◽  
Spin Lattice Relaxation ◽  
Zero Field ◽  
Triplet States ◽  
Spin Lattice

We present an overview over eight brightly luminescent Cu(I) dimers of the type Cu2X2(P∩N)3 with X = Cl, Br, I and P∩N = 2-diphenylphosphino-pyridine (Ph2Ppy), 2-diphenylphosphino-pyrimidine (Ph2Ppym), 1-diphenylphosphino-isoquinoline (Ph2Piqn) including three new crystal structures (Cu2Br2(Ph2Ppy)3 1-Br, Cu2I2(Ph2Ppym)3 2-I and Cu2I2(Ph2Piqn)3 3-I). However, we mainly focus on their photo-luminescence properties. All compounds exhibit combined thermally activated delayed fluorescence (TADF) and phosphorescence at ambient temperature. Emission color, decay time and quantum yield vary over large ranges. For deeper characterization, we select Cu2I2(Ph2Ppy)3, 1-I, showing a quantum yield of 81%. DFT and SOC-TDDFT calculations provide insight into the electronic structures of the singlet S1 and triplet T1 states. Both stem from metal+iodide-to-ligand charge transfer transitions. Evaluation of the emission decay dynamics, measured from 1.2 ≤ T ≤ 300 K, gives ∆E(S1-T1) = 380 cm−1 (47 meV), a transition rate of k(S1→S0) = 2.25 × 106 s−1 (445 ns), T1 zero-field splittings, transition rates from the triplet substates and spin-lattice relaxation times. We also discuss the interplay of S1-TADF and T1-phosphorescence. The combined emission paths shorten the overall decay time. For OLED applications, utilization of both singlet and triplet harvesting can be highly favorable for improvement of the device performance.

scholarly journals Exploiting trifluoromethyl substituents for tuning orbital character of singlet and triplet states to increase the rate of thermally activated delayed fluorescence

2020 ◽  
Vol 4 (12) ◽  
pp. 3602-3615 ◽  
Author(s):  
Jonathan S. Ward ◽  
Andrew Danos ◽  
Patrycja Stachelek ◽  
Mark A. Fox ◽  
Andrei S. Batsanov ◽  
...  
Keyword(s):  
Excited States ◽  
Organic Molecules ◽  
Delayed Fluorescence ◽  
Triplet States ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
Conjugated Organic Molecules ◽  
Singlet And Triplet States ◽  
Triplet Excited States ◽  
Orbital Character

This work shows that trifluoromethyl (CF3) substituents can be used to increase the rate of thermally activated delayed fluorescence (TADF) in conjugated organic molecules by tuning the excitonic character of the singlet and triplet excited states.

scholarly journals Exchange Interaction in Complex Bis[(1,3-Dithiole-2-Thione-4,5-Dithiolato)-di-(Carbonyl)-Cyclopentadienyl Iron(II)]

2009 ◽  
Vol 2009 ◽  
pp. 1-4
Author(s):  
S. V. Vitushkina ◽  
D. V. Ziolkovskiy ◽  
V. A. Starodub ◽  
I. A. Presniakov ◽  
A. V. Sobolev ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Triplet State ◽  
Temperature Dependence ◽  
Exchange Interaction ◽  
Spin Density ◽  
Wide Temperature Range ◽  
Electronic States ◽  
Dft Method ◽  
Triplet States ◽  
Singlet And Triplet States

The splitting of the quasidegenerate electronic states in dinuclear bis[(1,3-dithiole-2-thione-4,5-dithiolato)-di-(carbonyl)-cyclopentadienyliron (II)] complex with the bridging, S–S coupled, dimerized sulfur-rich dithiolate ligands, [Fe(C5H5)(CO)2(C3S5-C3S5)Fe(C5H5)(CO)2] (I) was found by the means of Mössbauer spectroscopy and by the measurement of the temperature dependence of magnetic susceptibility in a wide temperature range from 2 K to 300 K. The experimental results were confirmed by the calculations of the singlet and triplet states of the complex, as well as of the distribution of spin density within the bounds of the DFT method in the B3LYP/6-31(dp)G basis. In the more stable triplet state, the spin density is significantly delocalized, which is a characteristic of olefindithiolate complexes.

scholarly journals Organic Molecules with Inverted Gaps between First Excited Singlet and Triplet States and Appreciable Fluorescence Rates

2020 ◽  
Author(s):  
Robert Pollice ◽  
Pascal Friederich ◽  
Cyrille Lavigne ◽  
Gabriel dos Passos Gomes ◽  
Alan Aspuru-Guzik
Keyword(s):  
Excited State ◽  
Energy Difference ◽  
Delayed Fluorescence ◽  
Triplet States ◽  
Electron Hole ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Thermally Activated ◽  
Singlet And Triplet States

One of the recent proposals for the design of state-of-the-art emissive materials for organic light emitting diodes (OLEDs) is the principle of thermally activated delayed fluorescence (TADF). The underlying idea is to enable facile thermal upconversion of excited state triplets, which are generated upon electron-hole recombination, to excited state singlets by minimizing the corresponding energy difference resulting in devices with up to 100% internal quantum efficiencies (IQEs). Ideal emissive materials potentially surpassing TADF emitters should have both negative singlet-triplet gaps and appreciable fluorescence rates to maximize reverse intersystem crossing (rISC) rates from excited triplets to singlets while minimizing ISC rates and triplet state occupation leading to long-term operational stability. However, molecules with negative singlet-triplet gaps are extremely rare and, to the best of our knowledge, not emissive. In this work, based on computational studies, we describe the first molecules with negative singlet-triplet gaps and considerable fluorescence rates and show that they are more common than hypothesized previously.

Ab-initio Calculation on Methylnitrenium Ion (CH3NH)+

1974 ◽  
Vol 29 (5) ◽  
pp. 832 ◽  
Author(s):  
R. Gunde ◽  
A. Ažman
Keyword(s):  
Triplet State ◽  
Ab Initio ◽  
Ground State ◽  
Ab Initio Calculation ◽  
Triplet States ◽  
Singlet And Triplet States

Abstract Ab initio calculation were carried out on the singlet and triplet states of the methylnitrenium ion. The triplet state is the ground state for all values of angle at nitrogen.

Photophysical and Photochemical Properties of Some Fluorescent Derivatives of Vitamin B1

1987 ◽  
Vol 42 (5) ◽  
pp. 485-489 ◽  
Author(s):  
B. Marciniak
Keyword(s):  
Vitamin B1 ◽  
Emission Spectra ◽  
Photochemical Reactions ◽  
Triplet States ◽  
Excited Singlet ◽  
Yield Data ◽  
Singlet And Triplet States ◽  
Kinetics Of ◽  
Derivatives Of ◽  
Fluorescent Derivatives

Absorption and emission spectra, depopulation kinetics of the lowest excited singlet and triplet states and acid-base equilibria of two fluorescent vitamin B, derivatives, the products I and II of the reaction of N-methylated vitamine B, with cytidine and adenosine, respectively, were investigated. Analysis of the lifetime and quantum yield data indicate that at 77 K emissions are the main processes of deactivation of the S1 and T1 states for the free ion and protonated forms. The pKa values indicate a much higher acidity in the excited singlet and triplet states than in the ground state. I and II undergo very slow photochemical reactions in solution in the presence of oxygen (Φ ~ 10-4).

scholarly journals CNDO/S-CI Calculations of some Carbonyl-containing Organic Luminophores with a Stilbene Subchromophore

1985 ◽  
Vol 40 (8) ◽  
pp. 859-863
Author(s):  
G. Olbrich ◽  
P. Nikolov ◽  
F. Fratev ◽  
O. E. Polansky
Keyword(s):  
Quantum Yield ◽  
Fluorescence Quantum Yield ◽  
Electronic States ◽  
Solvent Polarity ◽  
Energy Separation ◽  
Triplet States ◽  
Organic Luminophores ◽  
Calculated Energy ◽  
Singlet And Triplet States ◽  
Ci Calculations

For a series of carbonyl-containing compounds with a stilbene subchromophore the lowest ten singlet and triplet states have been calculated with the aid of the CNDO/S-CI method. The results were used to rationalize the relative ordering of the lowest-lying S(ππ*), S(ππ*), T(ππ*), and T(ππ*) electronic states. Using the calculated energy separation between the singlet ππ*and nπ* states and between the singlet ππ* and triplet nπ* states the fluorescence ability of the compounds studied is interpreted. The connection between the structure of the compounds and their fluorescence is discussed. It is shown that an increase of the solvent polarity in some cases may lead to an inversion of the singlet nπ* and ππ* levels and to an enhancement of the fluorescence quantum yield.

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