Electron spin amines

Further aspects of the reaction of aromatic tertiary hydroxyl amines have been examined by more sophisticated techniques [49]. 2-Methyl-2-nitrosopropane was used as a radical trap, and the endgroups on PMMA resulting from its addition were detectable by ultraviolet spectroscopy. Electron spin resonance results on the same system have also been reported [50]. 

By far the most NMR studies have been concerned with the amine adducts of Ni(R-dtp)2 complexes. The green complexes formed with primary (mono-and bidentate) and heterocyclic (mono- und bidentate) amines and the yellow-brown five-co-ordinate adducts with secondly amines exhibit paramagnetic shifts in their NMR spectra. The use of paramagnetic NMR shifts in mapping unpaired electron spin distributions of paramagnetic complexes has been reviewed 378-381) jhe upfield paramagnetic shifts of NH protons are diagnostic... 

A number of adducts of bis(acetylacetonato)nickel(lI) have been studied by H and 13C NMR spectroscopy.39739,407"423 In several cases, always when aromatic bases are involved, the shifts of both protons and carbons cannot be accounted for by cr- and r-delocalization mechanisms. Similar results have been found for non-aromatic amines such as piperidine derivatives, showing that in these complexes there are also alternating 13C contact shifts which have been accounted for by inclusion of spin polarization in the mechanism of electron spin transfer through the carbon skeleton with INDO-MO calculations.412... 

Neta P, Fessenden RW (1971) Electron spin resonance study of radicals produced in irradiated aqueous solutions of amines and amino acids. J Phys Chem 75 738-748... 

Huttermann J, Ward JF, Myers LS Jr (1971) Electron spin resonance studies of free radicals in irradiated single crystals of 5-methylcytosine. Int J Radiat PhysChem 3 117-129 Huttermann J, Ohlmann J, Schaefer A, Gatzweiler W (1991) The polymorphism of a cytosine anion studied by electron paramagnetic resonance spectroscopy. Int J Radiat Biol 59 1297-1311 Hwang CT, Stumpf CL, Yu Y-Q, Kentamaa HI (1999) Intrinsic acidity and redox properties of the adenine radical cation. Int J Mass Spectrom 182/183 253-259 Ide H, Otsuki N, Nishimoto S, Kagiya T (1985) Photoreduction of thymine glycol sensitized by aromatic amines in aqueous solution. J Chem Soc Perkin Trans 2 1387-1392 Idris Ali KM, Scholes G (1980) Analysis of radiolysis products of aqueous uracil + N20 solutions. J Chem Soc Faraday Trans 176 449-456... 

Cai Z, Gu Z, Sevilla MD (2001) Electron spin resonance study of electron and hole transfer in DNA effects of hydration, aliphatic amine cations and histone proteins. J Phys Chem B 105 6031-6041 Cai Z, Li X, Sevilla MD (2002) Excess electron transfer in DNA effect of base sequence and proton transfer. J Phys Chem B 106 2755-2762... 

The separation (A) of the hyperfine lines in the ESR spectra of metal-amine, and metal-ether solutions represents a direct measure of the average s-electron (spin) density of the unpaired electron at the particular metal nucleus (12,156). When this splitting is compared to that of the free (gas-phase) atom, we obtain a measure of the "percent atomic character of the paramagnetic species. The percent atomic character in all these fluid systems increases markedly with temperature, and under certain circumstances the paramagnetic species almost takes on "atomic characteristics (43, 53, 160). Figure 9 shows the experimental data for fluid solutions of K, Rb, and Cs in various amines and ethers, and also for frozen solutions (solid data points) of these metals in HMPA (17). The fluid solution spectra have coupling con-... 

Second, it is conceivable that amines quench triplet ketones before spin-lattice relaxation takes place within the three triplet sublevels 159>, which are populated unevenly 160>. In that event, radicals can be produced with their electron spins polarized. The CIDEP phenomenon 161>, whereby EPR emission is observed upon irradiation of ketones and very reactive substrates, may involve this mechanism. In fact, certain CIDNP observations may depend on rapid quenching of spin-polarized triplets 162>. 

Electron Spin Resonance and Field Desorption - Mass Spectrometry Oxidation Studies of Partially Hindered Amines 3,3-Dialkyldecahydroquinoxalin-2-ones." by R. W. Layer, J. T. Lai, R. P. Lattimer and J. C. Westfahl, this symposium. 

Electron Spin Resonance and Field Desorption-Mass Spectrometry Oxidation Studies of Partially Hindered Amines... 

Fully hindered amines are excellent UV stabilizers, but poor thermal antioxidants, for polyolefins. We have found that partially hindered bicyclic amines, such as 3,3-dialkyldecahydroquinoxalin-2-ones, are excellent UV stabilizers and also excellent thermal antioxidants as well. The oxidation of these bicyclic amines with m-chloroperbenzoic acid was studied by electron spin resonance spectroscopy. They form stable, partially hindered nitroxyl radicals (6-line spectra). However, these primary radicals are easily oxidized to a new, fully hindered nitroxyl radical (3-line spectra) which are also very stable. Field desorption mass spectroscopic studies of the oxidation of these amines show that the primary nitroxyl radicals, which form first, lose two hydrogen atoms and add an oxygen. Thus, these bicyclic partially hindered amines are unique in being both stable and at the same time hydrogen atom donors. 

A recent LFP, electron spin resonance, and product study on the photodissociation of 7/-(triphenylmethyl)anilines concludes that the primary photochemical event is homolytic cleavage [72]. However, the chromophore in these molecules is the aromatic amine. Triphenylmethyl cations were observed when the excitation wavelength was 248 nm but these were apparently formed by a biphotonic process of electron photoejection from the triphenylmethyl radical. 

E.N. Step, J. Turro, M.E. Gande, and P.P. Klemchuck, Flash photolysis and time-resolved electron spin resonance studies triplet benzophenone quenching by hindered amine light stbilizers (HALS). A comparison of HALS amines and aminoethers and hydrogen atom donors, J. Photochem. Photobiool. A Chem. 1993, 74, 203-210. 

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