Die kinetischen Konstanten des Triplett-Zustandes von Fluoren-Molekülen / The Cinetic Constants of the Triplet Stale of Fluorene Molecules

AbstractThe metastable triplet state T1 of fluorene molecules in a fluorene crystal, disturbed by the presence of dibenzothiophene (“X-traps”) was investigated at 1.6 and 4.2 °K. From ESR measurements a model for the fluoren X-traps is derived. The X-trap molecule is misoriented by an angle of 2,5° in the fluorene crystal.The rate constants for population (s), radiative decay (kD) and total decay (k) of the three magnetic sublevels of T1 were determined by analysis of phosphorescence intensity and decay time in high magnetic field and by optically detected ESR. We find (with z = axis perpendicular to the molecule, x = long axis): The average spin lattice relaxation rate constant is w = (0.8 ± 0.2) sec- 1 .

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Photophysics of the lowest triplet state in 2-benzoylpyridine crystals. II. Optically detected e. p. r. in zero and high magnetic fields

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1979.0159 ◽

1979 ◽

Vol 369 (1737) ◽

pp. 187-206 ◽

Cited By ~ 4

Keyword(s):

Triplet State ◽

Rate Constants ◽

Radiative Decay ◽

Dynamic Properties ◽

Deep Trap ◽

Lattice Relaxation ◽

Spin Lattice Relaxation ◽

Zero Field ◽

Spin Lattice ◽

Optically Detected

Optically detected zero-field resonance has been used to characterize the intrinsic and deep trap 3 nπ * states in single crystals of 2-benzoylpyridine at 4.2 K. The dynamic properties of these states were studied by means of time-resolved modulated phosphorescence (t. r. m. p.) and estimates for the rate constants for depopulation and spin-lattice relaxation of the magnetic sub-levels obtained by computer simulation. For all species, depopulation from ז z dominates, having rates of order 100 s -1 , but the ז x and ז y sub-states have substantial radiative activity. The orientations of the fine-structure tensors of the magnetic species were determined from high-field e. p. r. spectra. Assuming that z is parallel to C = O, excitation causes the C = O direction to change by 8 ± 2° for the intrinsic species and by an in-significant amount for the deep trap. These spectra also demonstrated that the intrinsic triplet state is mobile. This species is believed to be a polaron with slow intersite hopping rate. A maximum energy transfer rate of 10 4 -10 5 s -1 was found for transfer between translationally inequivalent sites symmetry-related by twofold rotation about the crystal b -axis. Rate estimates for transfer to the other two translationally inequivalent sites established the two dimensional nature of the polaron. The sign and shape of the zero-field resonances for the intrinsic species were found to depend on whether excitation was through S 1 or T 1 . From the parameters required to simulate the corresponding t. r. m. p. signals it is inferred that the changes are largely due to differences in the rate constants for non-radiative decay. The deep trap was shown to have an orientation and magnetic properties similar to those of the intrinsic species, and is believed to be a physical defect. It has radiative activity from the ז x sub-level which is significantly less than for the intrinsic species. Spin-lattice relaxation is fast for the mobile intrinsic species ( ca . 10 4 s -1 ) compared with the deep trap rate ( ca . 50 4 s -1 ). For the intrinsic species a field dependence for spin-lattice relaxation is apparent.

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Optically Detected Spin Locking of Zero Field Electronic Triplet States and Cross Relaxation in the Rotating Frame

Zeitschrift für Naturforschung A ◽

10.1515/zna-1975-0316 ◽

1975 ◽

Vol 30 (3) ◽

pp. 361-371 ◽

Cited By ~ 3

Author(s):

H. Schuch ◽

C. B. Harris

Keyword(s):

Magnetic Field ◽

Lattice Relaxation ◽

Spin Lattice Relaxation ◽

Zero Magnetic Field ◽

Zero Field ◽

Triplet States ◽

Rotating Frame ◽

Spin Lattice ◽

Optically Detected ◽

Spin Locking

The spin locking method known from NMR is shown to be useful also in ESR for investigating spin lattice relaxation problems and “slow” motions, e. g. questions of energy transfer by triplet states in organic molecular crystals, and probing of nuclear quadrupolar splittings even smaller than the ESR line width at zero magnetic field.Optically detected ESR spin locking experiments for isolated triplet states in zero field are demonstrated. It is shown how the complication of incoming and decaying triplet states and relaxation between all three triplet sublevels has to be handled during spin locking. An application, the study of the cross-relaxation between electronic triplet spin states and deuteron or proton spins is presented. These experiments are possible in spite of the first order quenching of the hyperfine coupling in zero magnetic field. Another application is briefly mentioned, in which the adiabatically demagnetized state in the rotating frame is used to probe the electronic triplet state transfer and nuclear spin lattice relaxation.

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Magnetic field independence of Cu(2) NMR spin-lattice relaxation rate in the normal state of optimally dopedYBa2Cu3O7−δ

Physical Review B ◽

10.1103/physrevb.63.064513 ◽

2001 ◽

Vol 63 (6) ◽

Cited By ~ 5

Author(s):

K. R. Gorny ◽

O. M. Vyaselev ◽

C. H. Pennington ◽

P. C. Hammel ◽

W. L. Hults ◽

...

Keyword(s):

Magnetic Field ◽

Relaxation Rate ◽

Normal State ◽

Lattice Relaxation ◽

Spin Lattice Relaxation ◽

Field Independence ◽

Spin Lattice Relaxation Rate ◽

Spin Lattice ◽

Lattice Relaxation Rate

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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 ◽

10.3390/molecules26113415 ◽

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.

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