CIDEP measurement of the electron spin-lattice relaxation time of triplet benzophenone in liquid solution

Goudsmit, G.-H.; Paul, H.

doi:10.1016/0009-2614(96)00842-1

Cited by 10 publications

(10 citation statements)

References 25 publications

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“…At room temperature the rate of spin-lattice relaxation of the triplet sublevel is of the order of 1 ns for nonviscous solutions. [19] Since the time resolution of TREPR operating in the continuous wave (CW) mode is of the order of 100 ns, this technique cannot be used to probe the population of the selective triplet sublevel directly in fluid solutions. In addition, REVIEWS N. J. Turro et al…”

Section: Epr Spectroscopy Of T 1 Statesðsome General Considerationsmentioning

confidence: 99%

“…If the polarization found by TREPR (Figure 1) at 77 K is carried over at room temperature, and if a-cleavage can occur within REVIEWS Electron Spin Resonance in Photochemistry the spin-lattice relaxation time of the triplet state (ca. 1 ns), [19] then 1 a and related ketones should produce electron-spin polarized 2 ACO # and 2 B # radicals that can be observed in emission, and 2 (and related compounds) should produce electron spin polarized radicals that can be observed in absorption because angular momentum must be conserved (the superscript # signifies a polarized electronic spin). The general schemes for these two possibilities is shown in Scheme 8 a and b, respectively, while the experimental results obtained in fluid solution at room temperature are shown in Figures 2 and 3.…”

Section: Correlation Of the Trepr Of Molecular Triplets With Primary mentioning

confidence: 99%

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Electron Spin Polarization and Time-Resolved Electron Paramagnetic Resonance: Applications to the Paradigms of Molecular and Supramolecular Photochemistry

Turro

Kleinman

Karatekin

2000

Angew. Chem. Int. Ed.

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Most molecular and supramolecular organic photochemical reactions involve paramagnetic reactive intermediates (such as molecular triplet states, triplet radical pairs, and free radicals). In a number of cases these species are created with “anomalous” spin populations which are far from thermal equilibrium. Such paramagnetic species are said to be “spin polarized” and may be observed directly by time‐resolved electron paramagnetic resonance (TREPR). The TREPR technique can be applied to exploit spin polarization, which, in addition to providing an enormous signal to noise enhancement, also reveals the mechanisms involved in photochemical reactions. TREPR spectroscopy provides a means of tracking the reaction of radicals with molecules and the nonreactive interactions of radicals with other radicals in real time. The latter interactions provide a systematic investigation of supramolecular interactions of geminate radicals in micelles.

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Section: Epr Spectroscopy Of T 1 Statesðsome General Considerationsmentioning

confidence: 99%

Section: Correlation Of the Trepr Of Molecular Triplets With Primary mentioning

confidence: 99%

Electron Spin Polarization and Time-Resolved Electron Paramagnetic Resonance: Applications to the Paradigms of Molecular and Supramolecular Photochemistry

Turro

Kleinman

Karatekin

2000

Angew. Chem. Int. Ed.

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“…In general, a transient intermediate such as a photoexcited triplet is quenched by addition of a suitable compound and the effect of this upon reaction observed. Time-resolved EPR (TREPR) following flash photolysis is a widely used experiment for investigating radical photochemistry, however little work has been done with quenchers [2][3][4]. This is surprising as often a major problem in TREPR is the identification of the origin of net absorptive (A) contributions in spectra arising from triplet precursors, where quenching experiments should provide key information.…”

Section: Introductionmentioning

confidence: 99%

“…This polarisation may then be transferred to the radicals, if the triplet reacts before spin lattice relaxation (3/'1) has destroyed the polarisation. Fast reactions are therefore required, as 3Tl's are thought to be a few nanoseconds in solution [4][5][6][7][8]. However, net A contributions in TREPR spectra may also arise simply from the Boltzmann signal of the radicals or transfer of the Boltzmann polarisation of the triplet precursor.…”

Section: Introductionmentioning

confidence: 99%

Triplet and reversed triplet mechanism CIDEP studied by quenching experiments

1997

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Quenching experiments are shown to provide a convenient tool to check for the presence of triplet mechanism (TM) spin polarisation in time-resolved EPR spectra following laser flash photolysis. The effect of the triplet quenchers, trans-l,3-pentadiene, fumaronitrile, azo-tert-butane and azo-n-butane upon the spectra following laser photolysis of acetone/propan-2-ol and benzophenone/propan-2-ol photosystems show that no TM polarisation is present in the former system but emissive TM is present in the latter. Use of 2,2'-azo-bis[isobutryronitrile] produces an anomalous emissive polarisation upon quenching, which is tentatively attributed to a reversed TM in the tfiplet sensitised azo-compound.

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“…Assuming a very fast electron transfer from an excited state of [Ru(bpy)3] 2 § to an acceptor molecule, it might be possible, even at room temperature, that such a process is faster than spin-lattice relaxation (cf. [238,239]). In this case, a higher lying triplet sublevel might be more important for an electron transfer than the lowest excited state, which is often taken as the most probable candidate.…”

Section: Direct Processes Ofmentioning

confidence: 99%

Characterization of excited electronic and vibronic states of platinum metal compounds with chelate ligands by highly frequency-resolved and time-resolved spectra

Yersin

Humbs

Strasser

Topics in Current Chemistry

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The lowest excited electronic states of triplet character and related vibronic properties are discussed in detail on the basis of highly frequency-resolved and time-resolved emission and excitation spectra of per-protonated, per-deuterated, and partially deuterated [Pt(bpy)2] 2+, [Rh(bpy)3] 3+, [Ru(bpy)3] 2+, and [Os(bpy)3] ~+. Emphasis is placed on the use of the enormous amount of information displayed in well-resolved vibrational satellite structures. For comparison, IR data and Raman spectra are also used. In addition, data are given for [Ru(bpz)Pt(3-thpy) 2, Pt(2-thpy)(CO)(Cl), Pt(2-thpy) 2, Pt(qol)2, Pt(qtl)2. Trends and effects are also addressed, which are related to the amount of metal d-orbital mixing. In particular, we discuss the role of traps and sites in the context of high-resolution, site-selective, and line-narrowed spectra of chromophores doped into matrices; the interplay between states of ligand-centered 3rtrr* and ~MLCT character; localization versus delocalization behavior; radiative decay properties; zero-field splittings; spin-lattice relaxations via direct and Orbach mechanisms; Arrhenius behavior after time delay; Franck-Condon activities and Huang-Rhys factors; Franck-Condon versus Herzberg Teller activities and tunability of these activities under high magnetic fields; isotope marking and deuteration effects; aggregate formation of [Ru(bpy)3]2+; and radiationless energy transfer in neat [Ru(bpy)3](PF6) 2. These effects are in part treated in detail, but the aim is to use easy-to-follow descriptions. In particular, it is emphasized throughout this review that chemical tunability opens fascinating possibilities for controlled variation of physical properties.

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CIDEP measurement of the electron spin-lattice relaxation time of triplet benzophenone in liquid solution

Cited by 10 publications

References 25 publications

Electron Spin Polarization and Time-Resolved Electron Paramagnetic Resonance: Applications to the Paradigms of Molecular and Supramolecular Photochemistry

Electron Spin Polarization and Time-Resolved Electron Paramagnetic Resonance: Applications to the Paradigms of Molecular and Supramolecular Photochemistry

Triplet and reversed triplet mechanism CIDEP studied by quenching experiments

Characterization of excited electronic and vibronic states of platinum metal compounds with chelate ligands by highly frequency-resolved and time-resolved spectra

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