Radical pair formation from excited states in doped aromatic crystals. II. Optical nuclear polarization (ONP) studies

1979 ◽  
Vol 44 (1) ◽  
pp. 113-129 ◽  
Author(s):  
V. Macho ◽  
J.P. Colpa ◽  
D. Stehlik
Keyword(s):  
Excited States ◽  
Nuclear Polarization ◽  
Radical Pair ◽  
Pair Formation

scholarly journals Exploration of the close chemical space of tryptophan and tyrosine reveals importance of hydrophobicity in CW-photo-CIDNP performances

2021 ◽  
Vol 2 (1) ◽  
pp. 321-329
Author(s):  
Felix Torres ◽  
Alois Renn ◽  
Roland Riek
Keyword(s):  
Magnetic Field ◽  
Nuclear Polarization ◽  
Continuous Wave ◽  
Radical Pair ◽  
Chemical Space ◽  
Spin Dynamics ◽  
Basic Mechanism ◽  
Chemical Library ◽  
Chemically Induced ◽  
Small Chemical

Abstract. Sensitivity being one of the main hurdles of nuclear magnetic resonance (NMR) can be gained by polarization techniques including chemically induced dynamic nuclear polarization (CIDNP). Kaptein demonstrated that the basic mechanism of the CIDNP arises from spin sorting based on coherent electron–electron nuclear spin dynamics during the formation and the recombination of a radical pair in a magnetic field. In photo-CIDNP of interest here the radical pair is between a dye and the molecule to be polarized. Here, we explore continuous-wave (CW) photo-CIDNP (denoted CW-photo-CIDNP) with a set of 10 tryptophan and tyrosine analogues, many of them newly identified to be photo-CIDNP active, and we observe not only signal enhancement of 2 orders of magnitude for 1H at 600 MHz (corresponding to 10 000 times in measurement time) but also reveal that polarization enhancement correlates with the hydrophobicity of the molecules. Furthermore, the small chemical library established indicates the existence of many photo-CIDNP-active molecules.

Radical pair formation due to compression-induced electron transfer in crystals of energetic salts

2021 ◽  
Author(s):  
Sergey V. Bondarchuk
Keyword(s):  
Electron Transfer ◽  
Pressure Dependence ◽  
Radical Pair ◽  
Pair Formation ◽  
Energetic Salts

This puzzle illustrates how explosive and non-explosive salts can be separated using pressure-dependence of the cationic charges.

Photo-CIDNP Studies of 2-Butanone and 3-Pentanone in Solution

1974 ◽  
Vol 52 (16) ◽  
pp. 2978-2984 ◽  
Author(s):  
Shiv P. Vaish ◽  
Robert D. McAlpine ◽  
Michael Cocivera
Keyword(s):  
Electron Spin Resonance ◽  
Carbon Tetrachloride ◽  
Excited States ◽  
Nuclear Polarization ◽  
Radical Reactions ◽  
Electron Spin Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
Chemically Induced ◽  
Spin Resonance ◽  
Spin Polarized

The results of photolysis of 2-butanone and 3-pentanone as studied by chemically induced dynamic nuclear polarization (CIDNP) and electron spin resonance spectroscopy (e.s.r.) are reported. In aqueous solutions and t-butanol only the ethyl radical is detected by means of e.s.r., indicating α cleavage to be a major path involving excited states. This observation is further supported by the n.m.r. spectra which are obtained during irradiation of these ketones in D2O and a mixture of CD3CN–D2O (1:1 by volume) containing carbon tetrachloride. Several compounds are detected with their protons spin polarized. A mechanism involving radical reactions is proposed which is consistent with the experimental results.

Chemically Induced Dynamic Nuclear Polarization During Irradiation of Phenol in the Presence of Amides

1975 ◽  
Vol 53 (16) ◽  
pp. 2459-2464
Author(s):  
Shiv P. Vaish ◽  
Holger E. Chen ◽  
Micha Tomkiewicz ◽  
Robert D. McAlpine ◽  
Michael Cocivera
Keyword(s):  
Carbonyl Group ◽  
Spin Polarization ◽  
Dynamic Nuclear Polarization ◽  
Nuclear Spin ◽  
Nuclear Polarization ◽  
Radical Pair ◽  
Hydroxybenzoic Acid ◽  
Nuclear Spin Polarization ◽  
Ph Values ◽  
Chemically Induced

Irradiation of D2O solutions containing various phenols with aliphatic amides at pH values between 9 and 12 results in nuclear spin polarization which is observed as n.m.r. emission signals during irradiation. No polarization is observed for the phenols which include tyrosine, cresol, p-hydroxybenzoic acid, phenol, and others. For the amides which include acetamide, propionamide, N-methylacetamide, and N,N-dimethylacetamide, polarization was observed for only the protons on the carbon bonded to the carbonyl group. Because excited phenolate ions are known to eject electrons, it is proposed that the radical RĊ(O−)NR2 is formed by reaction of the amide with the hydrated electron. The polarization observed for the amides can be explained by reaction of RĊ(O−)NR2 with a benzosemiquinone radical via a radical pair.

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