E.S.R. Spectra

Tri-(l-naphthyl)phosphine is cleaved by alkali metals in THF solution. " Reaction with sodium gives the naphthalene radical-ion, with lithium the perylene radical-ion, and with potassium the radical-ion (22). Hydrocarbon radical-ion formation was thought to occur via naphthalene derived from the metal naphthalenide. E.s.r. spectra of further examples of phosphorus-substituted picrylhydrazyl radicals have been reported. ... 

Nitroxides have been shown to associate quite strongly with model hydroperoxides in the liquid phase (17.). We have now found evidence for NO /hydroperoxide group association in solid PPH films based both on the e.s.r. spectra of N0> species and... 

In contrast, when CH3N02 is exposed to radiation, neither CH3N02 nor CH3N02+ centres are formed [2]. We can be sure of this since the e.s.r. spectra of both these radical-ions have been thoroughly studied, and give well-defined spectra [3-4]. Instead, the major radicals detected by e.s.r. methods are CH3 and N02. These radicals, which are also formed by photolysis, are presumably formed by electron-return into an outer orbital followed by homolysis (3 and 4). In this case, electron or hole transfer, or... 

Sometimes it is possible to dope crystals with impurities which act as electron or hole traps, but if powder e.s.r. spectra suffice, it is convenient to use specific solvents to encourage either specific electron-capture or hole-capture by dilute solutions of suitable compounds. 

First-derivative X-band e.s.r. spectra for dilute solutions of methylcobaloxime after exposure to 60Co y-rays at 77 K ... 

Compounds of the type CpSnX3 (X = alkyl, Cp, Cl) are very photosensitive compared with alkyltin compounds, and on irradiation show strong E.S.R. spectra of the Cp-radical54. The equivalent silicon and germanium compounds do not show this reactivity (reaction 34). 

Miscellaneous spectral studies include e.s.r. spectra of chloro-phosphines (2)6 and vibrational spectra of various phosphines.6-8 N.m.r. studies include those of borane complexes of aryldichlorophosphines,9 and studies of the conformation of dichloro-(isopropyl)phosphine (3)10 and dichloro(ethyl)phosphine (4).10 These phosphines have the preferred conformations shown. Conformation has also been the theme of electron-diffraction work on the anhydride (5), which appears to have a staggered conformation.11 The electronic implications of a relatively short P—O bond and wide POP angle have been discussed.11... 

The e.s.r. spectra of phosphorus compounds have been reviewed.101 The phosphorus hyperfine splitting (ap 33.5 G) of the radical anion (77) is within the 25—36 G range of phosphorin radical anions.102 The cis- and fra/w-isomers of 1,2-bisdiphenylphos-phinoethylene gave the same radical anion (78). The unpaired electron is coupled to all the protons in the molecule as well as to the two phosphorus atoms, and shows that the electron is completely delocalized. Only when caesium was used as the gegenion in THF could a metal interaction be detected. The spectrum in this case corresponded to the association of two caesium ions with the radical anion, the third... 

The e.s.r. spectra of y-irradiated diethyl phosphate and its salts have been studied111 and the structures of the phosphonates(89)112 and some nucleoside phosphates113 have been studied from the e.s.r. spectra of the nitroxide spin-labelled compounds. An e.s.r. study of electron transfer in dinucleoside phosphate anions indicates preferen-... 

Electron-spin resonance (e.s.r.) spectra with characteristic hyperfine structure have been recorded during the initial stages of the Maillard reaction between various sugar and amino compounds. The products responsible for the spectra appear to be IV, Af -disubstituted pyrazine radical cations. The pyrazine derivatives are assumed to be formed by the bimolecular condensation of two- and three-carbon enaminol compo-... 

A series of oxovanadium(iv) carboxylates V0(RC02)2 (RCO2 = acetate, propionate, butyrate, isobutyrate, valerate, pivalate, phenylacetate, benzoate, or w-chlorobenzoate) have been prepared by the reaction of freshly prepared hydrated V2O4 with a mixture of the corresponding acid and anhydride in toluene or DMF solution, and/or by the reaction of VOCI2 and the corresponding carboxylic acid in aqueous solution. I.r., electronic, and e.s.r. spectra... 

The e.s.r. spectra obtained for several oxovanadium (iv) complexes, including [VO(acac)2], orientated in nematic glasses, compare favourably with those obtained by dilute single-crystal procedures.X-Band e.s.r. spectra of magnetically dilute glasses at 77 K show that EtOH and py form weak complexes with [VO(P-dik)] molecules [P-dik = acac, bzac, tropolone, 3-bromotropolone, (35), or (36)], and that vanadium(iv) in solutions of these... 

N-Donor Ligands. E.s.r. spectra of the [V(NEt2) ]-EtAlCl2 system, in heptane solution, have shown that the olefin polymerization catalysts are the 1 1 or 1 2 adducts, which are formed for V A1 ratios of greater or less, respectively, than 4 1. OClj reacts with ammonia at room temperature to give [VO(NH3)5]Cl2. which appears to involve weak V=0---------V=0-------inter-... 

Good evidence for the formation of dimeric 4,4, 4",4 "-tetrasulphophthalo-cyanine oxovanadiumtiv) species in HjO-DMF solutions has been obtained from e.s.r. spectra, and the metal centres are estimated to be 450 pm apart. In aqueous solution, although dimers are present, most of the oxovanadium(iv) complexes are polymerized, and in DMF solution substantial amounts of monomer exist. Stability constants for the formation of 1 1 complexes between pyridine and some oxovanadium(iv)-2,4-disubstituted deuteriopor-phyrin dimethyl esters have been determined in chloroform solution at 25 °C. Magnetic and spectroscopic evidence suggest the presence of an electronic interaction between centres in these compounds. 

Dilute single-crystal e.s.r. spectra have been obtained for [(jr-Cp)2VCl2] in [(n-Cp)2TiCl2]. The experimental results were interpreted using MO calculations which indicate that the unpaired electron is in an a -type MO... 

N-, P-, As-, and Sh-donor Ligands. [Cr(CO) (bipy)] has been reduced by sodium in THF. Electronic and e.s.r. spectra of the resulting complex suggest that it involves co-ordination of the uni-negative ion of bipy. The complex loses CO to afford either a five-co-ordinate complex or a dimeric species. ... 

A detailed study of the electronic, vibrational, and e.s.r. spectra of a series of substituted dipyrromethane complexes of nickel(ii) has been reported." The reduction of the nickel(ii) 1,19-diethoxycarbonyltetradehydrocorrin cation with a sodium film in THF under high vacuum gives both one- and two-electron reduction products. The one-electron reduction product is a very stable free radical, and the other product is formulated as a Ni" species with the two extra electrons located in ligand n-orbitals. The structures of nickel-(ii)-octaethylporphin and nickel(ii)-deoxophylloerythrin methyl ester-1,2-... 

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