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

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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P^N bridged Cu(I) Dimers Featuring both TADF and Phosphorescence. From Overview Towards Detailed Case Study of the Excited Singlet and Triplet States.

10.20944/preprints202104.0294.v1 ◽

2021 ◽

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(PN)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 varies 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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Time Domain Zero Field NMR and NQR

Zeitschrift für Naturforschung A ◽

10.1515/zna-1986-1-286 ◽

1986 ◽

Vol 41 (1-2) ◽

pp. 440-444 ◽

Cited By ~ 1

Author(s):

A. Bielecki ◽

D. B. Zax ◽

A. M. Thayer ◽

J. M. Millar ◽

A. Pines

Keyword(s):

Time Domain ◽

Relaxation Times ◽

Low Frequency ◽

High Sensitivity ◽

Lattice Relaxation ◽

Spin Lattice Relaxation ◽

Zero Field ◽

Spin Lattice ◽

Field Cycling ◽

The Time Domain

Field cycling methods are described for the time domain measurement of nuclear quadrupolar and dipolar spectra in zero applied field. Since these techniques do not involve irradiation in zero field, they offer significant advantages in terms of resolution, sensitivity at low frequency, and the accessible range of spin lattice relaxation times. Sample data are shown which illustrate the high sensitivity and resolution attainable. Comparison is made to other field cycling methods, and an outline of basic instrumental requirements is given.

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The determination of zero-field splittings from measurements of spin-lattice relaxation times

Journal de Physique Lettres ◽

10.1051/jphyslet:0197400350507300 ◽

1974 ◽

Vol 35 (5) ◽

pp. 73-76 ◽

Cited By ~ 5

Author(s):

A.M. Vasson ◽

A. Vasson ◽

A. Gavaix ◽

T.S. Yalcin ◽

P. Steggles ◽

...

Keyword(s):

Relaxation Times ◽

Lattice Relaxation ◽

Spin Lattice Relaxation ◽

Zero Field ◽

Spin Lattice

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An electron spin resonance and CIDEP study of the primary processes in the photoreductions of furaldehyde, furyl methyl ketone, and acetylthiophene by phenols

Canadian Journal of Chemistry ◽

10.1139/v81-018 ◽

1981 ◽

Vol 59 (1) ◽

pp. 116-122 ◽

Cited By ~ 8

Author(s):

Kuang S. Chen ◽

Jeffrey K. S. Wan

Keyword(s):

Double Bond ◽

Methyl Ketone ◽

Relaxation Times ◽

Lattice Relaxation ◽

Spin Lattice Relaxation ◽

Triplet States ◽

Time Resolved ◽

Spin Lattice ◽

Carbon Double Bond ◽

Photochemical Systems

The primary processes in the photoreduction of 2-furaldehyde, 2-furyl methyl ketone, and 2-acetylthiophene by phenol, 2,6-di-tert-butylphenol, and pentachlorophenol, respectively, were studied by esr and time-resolved CIDEP techniques. These furan derivatives, in their excited triplet states, can abstract a hydrogen atom from phenol via either the carbonyl group or the carbon–carbon double bond. The present results suggest that they all behave in the primary processes predominantly as carbonyl compounds. The spin–lattice relaxation times of all transient and polarized radicals observed in these photochemical systems were estimated by the CIDEP technique. The photoreductions of furaldehyde and furyl methyl ketone were also examined by high-field CIDNP. The nuclear polarization is mainly due to the cage products and the results are consistent with triplet carbonyl abstraction mechanism. Secondary radical addition to the carbon–carbon double bond of the furan ring was also observed in the furaldehyde–phenol system.

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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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Optische Elektronenspin-Polarisation (OEP) in Triplett-Zuständen organischer Moleküle

Zeitschrift für Naturforschung A ◽

10.1515/zna-1970-1005 ◽

1970 ◽

Vol 25 (10) ◽

pp. 1383-1394 ◽

Cited By ~ 7

Author(s):

H. Sixl ◽

M. Schwoerer

Keyword(s):

Spin Polarization ◽

Lattice Relaxation ◽

Microwave Emission ◽

Spin Lattice Relaxation ◽

Electron Spin Polarization ◽

Zero Field ◽

Triplet States ◽

Spin Lattice ◽

Optical Electron ◽

Methyl Naphthalene

Abstract Stimulated microwave emission is observed in the ESR spectrum of 2-methyl-naphthalene and anthracene molecules in their triplet states at 4,2 °K. This is the consequence of a strong deviation from thermal equilibrium distribution within the three magnetic sublevels, a phenomenon called optical electron spin polarization (OEP). The OEP is due to spin selection rules either during the population or during the depopulation processes of the triplet states. In most cases both processes occour predominantly radiationless and are termed intersystem-crossing (ISC).In the present paper we report in detail about the kinetics of population, depopulation and spin-lattice relaxation of the phosphorescent triplet states of 2-methyl-naphthalene and anthra-cene. In addition the kinetical constants, the fine structure constants and the orientation in the host crystal of eleven different metastable triplet state molecules are presented in a table.As opposed to former investigations (quinoxaline, naphthalene, pyrazine) spin polarization in 2-methyl-naphthalene and anthracene is due to the selectivity of the depopulation mechanism. This is demonstrated by the time dependence of the ESR-signals after switching on and off ex-citation light. The evaluation of the experiments yields a common rule concerning the intrinsic zero-field decay rate constants of naphthalene, 2-methyl-naphthalene and anthracene:kx : ky : kz ≈ 2 : 1 : 0,2The selectivity of the population decreases in the sequence naphthalene, 2-methyl-naphthalene, anthracene.

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