Electron spin resonance spectra compounds

Another difference is that the 5/ orbitals have a greater spatial extension relative to the 6,s and 6

electron-spin resonance spectrum of UF3 in a CaF2 lattice shows structure attributable to the interaction of fluorine nuclei and the electron spin of the U3+ ion. This implies a small overlap of 5/ orbitals with fluorine and constitutes an/covalent contribution to the ionic bonding. With the neodymium ion a similar effect is not observed. Because they occupy inner orbitals the 4/ electrons in the lanthanides are not accessible for bonding purposes and virtually no compound in which 4f orbitals are used can be said to exist. 

Amavadin shows the characteristic electron spin resonance spectrum of tetravalent vanadium which can be used to follow isolation. The ESR spectrum is the same before and after isolation (ref.4). Therefore it is clear that no binding to a protein is occurring. The molecular weight determination reveals that amavadin is a low molecular weight compound of approximately 420 + 20 dalton. 

Crystals of the product obtained by this method may be weighed and handled in air although they should be stored and used in further reactions under an inert atmosphere. The compound is only very sparingly soluble in common organic solvents. It is paramagnetic and its electron spin resonance spectrum at room temperature and 77 K has been reported. Its infrared spectrum... 

Solutions of sodium-naphthalene in tetrahydrofuran are dark green, electrically conducting because the compound is a salt Na (THF) CioHs", and paramagnetic because of the extra electron which is in a singly occupied 7r-orbital. Information about the distribution of the unpaired electron about its various possible positions in the anion can in suitable cases be derived from the electron spin resonance spectrum. If the orbital occupied by the unpaired electron in a hydrocarbon anion is non-degenerate, as is the case with naphthalene and anthracene, then a second electron (formation of anion ) would enter the same orbital and both the paramagnetism and e.s.r. spectra disappear. 

As with the nitroxalkylcobalamins (119) and cobinamides, the co-binamides in which nitroxide is coordinated show electron spin resonance spectra very similar to the spectrum of free nitroxide. The high field line is not broadened as much as in the spectrum of a nitroxalkyl-cobinamide. No hyperfine splitting from methyl protons in the 2 or 6 positions can be observed for the bound nitroxide. However, treatment of the coordinate spin labeled compounds with cyanide releases the nitroxide. When this happens, the proton hyperfine can be observed (Fig. 25). Thus treatment with cyanide simply displaces the nitroxide and a spectrum for free nitroxide is observed. 

In the anion-radicals of nitro compounds, an unpaired electron is localized on the nitro group and this localization depends on the nature of the core molecule bearing this nitro substituent. The value of the hyperfine coupling (HFC) constant in the electron-spin resonance (ESR) spectrum reflects the extent of localization of the unpaired electron values of several nitro compounds are given in Table 1.1. 

The effect of temperature on the association of vanadium compounds in asphaltenes was investigated by Tynan and Yen (1969). Using electron spin resonance (ESR), they observed both anisotropic and isotropic hyperfine structures of vanadium, interpreted as bound or associated and free vanadium, from asphaltenes precipitated for a Venezuelan petroleum and reintroduced to various solvents. Higher temperatures and more polar solvents resulted in a transition from bound to free vanadium, as shown in Fig. 12. At 282°C, only 1% of the anisotropic spectrum was observed. An activation energy of 14.3 kcal/mole was observed for the transition. 

It should be stressed that electron-spin resonance can occur only for molecules with unpaired electrons. This is a severe limitation in the sense that very few pure organic compounds contain such molecules and often these have to be prepared and stored under very special conditions. Thus, in contrast with the related technique of nuclear magnetic resonance (n.m.r.), this will never be of much importance to the analytical chemist. In one sense, however, this restriction is a virtue since, however complex a system may be, only those molecules which are paramagnetic will contribute to the spectrum. 

Historically, the triphenylmethyl radical (1), studied by Gomberg in 1987, is the first organic free radical. The triphenylmethyl radical can be obtained by the reaction of triphenylmethyl halide with metal Ag as shown in eq. 1.1. This radical (1) and the dimerized compound (2) are in a state of equilibrium. Free radical (1) is observed by electron spin resonance (ESR) and its spectrum shows beautiful hyperfine spin couplings. The spin density in each carbon atom can be obtained by the analysis of these hyperfine spin coupling constants as well as information on the structure of the free radical. 

Haemoglobin fluoride is an 5 = 1 iron(III) compound known from electron-spin resonance data to have the 5 = 1> Kramers doublet lying lowest. Spectra between 195 K and 1-2 K show appreciable spin-spin and spin-lattice relaxation effects. The examples in Fig. 13.7 can be compared with the predicted line spectrum. Surprisingly, the spectrum sharpens in... 

Rode et al. (107) carried out an electron spin resonance study of the intermediate oxides formed in the thermal decomposition of chromic anhydride. Chromium decachromate, chromium dichromate, and chromium hydroxide at room temperature, as well as the ferromagnetic compounds chromium monochromate and chromium dioxide above their Curie points at 130°, give symmetrical absorption lines 130 to 160 gauss wide with a g factor of 1.97, Shnkin and Fedorovskaia (108) studied CrgOa containing lithium, and detected fine structure in the ESR spectrum. 

Spectral Database for Organic Compounds (SDBS) is an integrated spectral database system for organic compounds, which includes six different types of spectra, an electron-impact mass spectrum (EI-MS), a Fourier transform infrared spectrum (FT-IR), a H NMR spectrum, a NMR spectrum, a laser Raman spectrum, and an electron spin resonance (ESR) spectrum [72], SDBS is maintained by the National Metrology Institute of Japan (NMU) under the National Instimte of Advanced Industrial Science and technology (AIST). Currently, EI-MS spectrum, H NMR spectrum, C NMR spectrum, FT-IR spectrum, and the compound dictionary are... 

The catalyst for the styrene polymerization is prepared by the mixing of a compound with MAO. The catalytic activity of Cp Ti(OMe)3 is increased by the mixing time under room temperature, and the intensity of the electron spin resonance (ESR) spectrum (g=1.998) also showed an increase of the trivalent titanium species (Fig. 4.6). The polymerization activity of a titanium catalyst increases with an increase in the molar ratio of MAO to Ti. 

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