Recent Developments in Studies of Electronic Excited States by Means of Electron Paramagnetic Resonance Spectroscopy

Yamauchi, Seigo

doi:10.1246/bcsj.77.1255

Cited by 38 publications

(36 citation statements)

References 47 publications

(26 reference statements)

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“…The original discussion of these results (35) assumed that the absorption Lorentzian-like line shape appearing at high temperatures is mainly due to thermal relaxation (SLR). Such explanation provided good fit to the experimental results but does not account for emissive spectra found under similar conditions in triplets such as H 2 TPP and MgTPP (36). An alternative explanation for the apparent thermalization of the spectrum is through very fast rotations about all the molecular axes, similar to the mechanism employed earlier for the C 60 case (13).…”

Section: Applications and Examplesmentioning

confidence: 74%

Triplet line shape simulation in continuous wave electron paramagnetic resonance experiments

Blank¹,

Levanon²

2005

Concepts Magn. Reson.

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ABSTRACT:We present a simple yet powerful method of simulating continuous wave electron spin resonance line shape of triplets in frozen and liquid solutions. The analysis enables one to consider cases such as immobilized triplets with random distribution, anisotropic slow and fast rotation of the triplet molecules, exchange between triplets with different Hamiltonians, anisotropic relaxation rates, and triplets with non-Boltzmann population distribution of the spin levels. Theoretical basis for the method is provided, along with several examples of simulated and experimental spectra for various physical conditions. A short "Matlab" routine, which can be used in the numerical spectra simulation, is given in the Appendix.

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Section: Applications and Examplesmentioning

confidence: 74%

Triplet line shape simulation in continuous wave electron paramagnetic resonance experiments

Blank¹,

Levanon²

2005

Concepts Magn. Reson.

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“…Such dipolar mixing also maygenerate anet polarization for the transition between j D + 1/2 > and j D À1/2 > near the center of the spectrum. [13,[61][62] Hereafter,w ew ill use the ket vectors j D Ms > or j Q Ms > to express the doublet or quartet state, respectively,w ith am agneticq uantum number M s .T his mechanism is expected to be effective in the case of small/ moderate exchange interaction (J), as the mixingi si nversely proportional to the energy splitting between the Da nd Q states (2J = DE DQ = E(D)ÀE(Q)). However,i np-conjugated spin systemss uch as p-radicals, the magnitude of the exchange interaction J is much larger than that of the dipolar interaction.…”

Section: Eisc In Chromophore-linked P-radicalsmentioning

confidence: 99%

Excited‐State Dynamics of Non‐Luminescent and Luminescent π‐Radicals

Teki

2019

Chemistry A European J

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Recently,t he potentialu se of organic p-radicals and relateds pin systems has been expanded to modern technological applications. The unique excited-state dynamics of organic p-radicals can be useful to improvet he stability of photochemically unstable organic compounds, make the polarization transfer applicable to information technology,a nd achieve effective up-conversion of interest for luminescence bioimaging, amongo thers. Furthermore, highly luminescent stable p-radicalsh ave been recently reported, which are especially interesting fora pplication in organic light-emitting devices owing to their potentialt op rovide an internal quantum efficiency of 100 %. Thus,t he excited-state nature of stable p-radicalsa sw ell as the control of their excited-state spin dynamics are emerging topics both in terms of fundamental science and related technological applications. In this minireview,w ef ocus on the excited-state dynamics of both photostable non(weakly)-luminescent and luminescent p-radicals, which are opposites of each other.I n particular, we cover the following topics:1 )effective generation of high-spin photoexcited states and control of the excited-state dynamics by using non-luminescent p-radicals, 2) unique excited-state dynamics of luminescent p-radicals and radical excimers, and 3) applicationsu tilizing excitedstate dynamics of p-radicals.[a] Prof.

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“…The simulation allowed us to estimate the zero-field splitting parameters as D = (À3/2)E z = 0.93 GHz and 2E = E x ÀE y = 0.0 GHz, which are typical values for the excited triplet states of porphyrins. [38,39] The population ratio of the sublevel for P x /P y /P z was 0.0:0.2:0.8. The deviation of the signal from the simulation may result from fast excitation hopping over the porphyrin arrays in the PNC crystals.…”

Section: A C H T U N G T R E N N U N G (H 4 Dppmentioning

confidence: 99%

Selective Inclusion of Electron‐Donating Molecules into Porphyrin Nanochannels Derived from the Self‐Assembly of Saddle‐Distorted, Protonated Porphyrins and Photoinduced Electron Transfer from Guest Molecules to Porphyrin Dications

Kojima

Nakanishi

Harada

et al. 2007

Chemistry A European J

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A doubly protonated hydrochloride salt of a saddle-distorted dodecaphenylporphyrin (H2DPP), [H4DPPP]Cl2, forms a porphyrin nanochannel (PNC). X-ray crystallography was used to determine the structure of the molecule, which revealed the inclusion of guest molecules within the PNC. Electron-donating molecules, such as p-hydroquinone and p-xylene, were selectively included within the PNC in sharp contrast to electron acceptors, such as the corresponding quinones, which were not encapsulated. This result indicates that the PNC can recognize the electronic character and steric hindrance of the guest molecules during the course of inclusion. ESR measurements (photoirradiation at lambda>340 nm at room temperature) of the PNC that contains p-hydroquinone, catechol, and tetrafluorohydroquinone guest molecules gave well-resolved signals, which were assigned to cation radicals formed without deprotonation based on results from computer simulations of the ESR spectra and density functional theory (DFT) calculations. The radicals are derived from photoinduced electron transfer from the guest molecules to the singlet state of H4DPP2+. Transient absorption spectroscopy by femtosecond laser flash photolysis allowed us to observe the formation of 1(H4DPP2+)*, which is converted to H4DPP+. by electron transfer from the guest molecules to 1(H4DPP2+)*, followed by fast disproportionation of H4DPP+., and charge recombination to give diamagnetic species and the triplet excited state 3(H4DPP2+)*, respectively.

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Recent Developments in Studies of Electronic Excited States by Means of Electron Paramagnetic Resonance Spectroscopy

Cited by 38 publications

References 47 publications

Triplet line shape simulation in continuous wave electron paramagnetic resonance experiments

Triplet line shape simulation in continuous wave electron paramagnetic resonance experiments

Excited‐State Dynamics of Non‐Luminescent and Luminescent π‐Radicals

Selective Inclusion of Electron‐Donating Molecules into Porphyrin Nanochannels Derived from the Self‐Assembly of Saddle‐Distorted, Protonated Porphyrins and Photoinduced Electron Transfer from Guest Molecules to Porphyrin Dications

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