Solvent influence on the magnetic field effect of polymethylene-linked photogenerated radical ion pairs

Busmann, H.‐G.; Staerk, H.; Weller, A.

doi:10.1063/1.457624

Cited by 66 publications

(36 citation statements)

References 28 publications

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“…In such RIPs having a long D-A distance, the exchange interaction may be so small that ISC from the singlet to the triplet states is reduced by H, as shown in solution [27,28] and at crystal surfaces [29]. Since the population of the singlet RIPs relative to that of the triplet RIPs becomes higher in the presence of H, exciplex fluorescence reduced by F is recovered to some extent in the presence of H; E-F-I-Q of the exciplex fluorescence becomes less in the presence of H. As already mentioned, it is also considered that fluorescent exciplex in type (I) is formed not only from RIP produced by PIET but also from a contact pair of the LE state, i.e., (D*…A) in Figure 1, since E-F-I-Q of the LE fluorescence, which leads to E-F-I-E of the number of RIPs produced by PIET, does not induce an enhancement of the exciplex fluorescence [61].…”

Section: Discussionmentioning

confidence: 99%

Magnetic field effects on electro-photoluminescence of photoinduced electron transfer systems in a polymer film

Awasthi

Ohta

2011

Journal of Photochemistry and Photobiology A: Chemistry

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Magnetic field effects on photoluminescence (PL) in the presence of external electric fields have been examined for a variety of electron donor and acceptor pairs, either linked with methylene chain or randomly distributed in polymethyl methacrylate (PMMA) films, which show intermolecular photoinduced electron transfer (PIET). Application of electric fields changes the energy separation among different electronic states, because the electric dipole moment at the state under consideration is usually different from the others. The energy levels within the same spin multiplicity are also shifted or splitted by application of magnetic field. Then, simultaneous application of electric field and magnetic field induces interesting effects on PL which cannot be observed when only electric field or magnetic field is applied to molecules. In this article, experimental results of the magnetic field effect of the electric field effect both on LE fluorescence and on exciplex fluorescence resulting from PIET are presented, and the mechanism of the synergy effects of the electric and magnetic fields on PL are discussed. The hyperfine interaction of the various radical-ion pairs produced by PIET has been also determined on the basis of the synergy effects on PL, and the results are compared with the calculated values.

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Section: Discussionmentioning

confidence: 99%

Magnetic field effects on electro-photoluminescence of photoinduced electron transfer systems in a polymer film

Awasthi

Ohta

2011

Journal of Photochemistry and Photobiology A: Chemistry

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“…Therefore, the exchange energy ( J ) of these two electrons at HOMO and LUMO can be calculated by Equation :

J = \int true \int ϕ_{L} (1) ϕ_{H} (2) (\frac{e^{2}}{r_{1} - r_{2}}) ϕ_{L} (2) ϕ_{H} (1) d r_{1} d r_{2}

where φ H and φ L represent the HOMO and LUMO wave functions, respectively; e is the electron charge. From Equation , it is clear that a small Δ E ST can be resulted via a small overlap integral of <φ H |φ L >, i.e., via spatial wave function separation of HOMO and LUMO …”

Section: Key Tadf Processesmentioning

confidence: 99%

Thermally Activated Delayed Fluorescence Materials Towards the Breakthrough of Organoelectronics

et al. 2014

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The design and characterization of thermally activated delayed fluorescence (TADF) materials for optoelectronic applications represents an active area of recent research in organoelectronics. Noble metal-free TADF molecules offer unique optical and electronic properties arising from the efficient transition and interconversion between the lowest singlet (S1 ) and triplet (T1 ) excited states. Their ability to harvest triplet excitons for fluorescence through facilitated reverse intersystem crossing (T1 →S1 ) could directly impact their properties and performances, which is attractive for a wide variety of low-cost optoelectronic devices. TADF-based organic light-emitting diodes, oxygen, and temperature sensors show significantly upgraded device performances that are comparable to the ones of traditional rare-metal complexes. Here we present an overview of the quick development in TADF mechanisms, materials, and applications. Fundamental principles on design strategies of TADF materials and the common relationship between the molecular structures and optoelectronic properties for diverse research topics and a survey of recent progress in the development of TADF materials, with a particular emphasis on their different types of metal-organic complexes, D-A molecules, and fullerenes, are highlighted. The success in the breakthrough of the theoretical and technical challenges that arise in developing high-performance TADF materials may pave the way to shape the future of organoelectronics.

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“…Some contrasting conclusions have been reported for¯exibly linked radical pairs. Whereas Bittl and Schulten [52] found no di erence between distance-dependent and distance-inde pendent electron transfer, an observatio n which they assigned to the e ect that the stochastic motion averages the decay rates in the various conformations of the biradical to one e cient decay rate, Staerk et al [55] found it essential to use contact reaction behaviou r in order to reproduce the experimental results. This was not possible with distance independen t recombination.…”

Section: Introductionmentioning

confidence: 99%

Magnetic field effect as a probe of distance-dependent electron transfer in systems undergoing free diffusion

KRISSINEL¹

1999

Molecular Physics

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A theoretical analysis is presented of the problem of how distance-dependent electron transf er in photoinduced forward electron transfer followed by geminate backward electron transfer in liquid solution is re¯ected in the viscosity dependence of the magnetic ® eld e ect ( MFE) on the e ciency of free radical formation u ce in such reactions. The stochastic Liouville equation formalism is employed to model the reaction behaviour of distance-distributed, triplet-born radical pairs ( R Ps) undergoing free di usion, distance-and spin-dependent backward electron transfer, coherent and incoherent spin evolution in the ps time domain. In comparison with real systems the spin situation is simpli® ed by reducing it to a two state S , T 0 problem, yet it is parametrized in a way that allows sensible comparison of the results with those of recent experiments. It is predicted that the MFE on u ce exhibits characteristic minima in the MFE versus viscosity curves, and it is veri® ed in detail that this f eature is peculiar to the di usional model with distance-dependent electron transfer, i.e. cannot be reproduced with the simpler (`exponential') R P model employing distance-independent rate constants. Thus, the MFE versus viscosity curves are established as a genuine ® ngerprint of distance-dependent electron transfer. The theoretical results compare f avourably with recent experimental results obtained with R u III complex/methylviologen RPs.

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Solvent influence on the magnetic field effect of polymethylene-linked photogenerated radical ion pairs

Cited by 66 publications

References 28 publications

Magnetic field effects on electro-photoluminescence of photoinduced electron transfer systems in a polymer film

Magnetic field effects on electro-photoluminescence of photoinduced electron transfer systems in a polymer film

Thermally Activated Delayed Fluorescence Materials Towards the Breakthrough of Organoelectronics

Magnetic field effect as a probe of distance-dependent electron transfer in systems undergoing free diffusion

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