1,721,130 research outputs found
ESR of free radical reactions in gamma-irradiated ethylene–propylene-based terpolymers. II
No full textThe gamma irradiation at liquid nitrogen temperature of dicyclopentadiene, 2-methylennorbornene, and cyclopentadienyl-5-endo-norbor-2-enyl-methane-based ethylene–propylene terpolymers leads to the formation of macroradicals of the alkyl type by loss of hydrogen atoms from the ethylene–propylene chains. When warmed almost to glass transition temperature these primary alkyl species decay and generate new radicals by the double-bond addition and/or H abstraction from the unsaturations. The nature of the radical products was determined by ESR and MO methods
ESR study of paramagnetic centres in irradiated platinum complexes
No full textPlatinum dichloride complexes with diolefins and phosphines were γ-irradiated at 77K and studied by ESR spectroscopy. Several paramagnetic species were simultaneously produced by electron capture, electron loss and bond homolysis in the pure compounds. An high selectivity in the generation of the reduced species was reached by the irradiation at 77K of the metal complexes in methyltetrahydrofuran solutions. The ESR spectra analysis of the paramagnetic Pt(I) species suggested a SOMO of σ-antibonding character for diolefins complexes and 7π-out-of-plane character for phosphine complexes
EPR Investigation of sulphur radicals in the mechanism of accelerated sulphur vulcanization of SBR elastomers.
No full text
Matrix isolation and ESR study of unstable intermediate generated by radiation techniques from metal carbonyl complexes
No full textExposure of MeTHF solutions of M(CO)6 (M=Cr, Mo, W) to γ-rays or photoionization with TMPD at 77 K gives paramagnetic species attributed to 17 electron radical anions M(CO) . The excess energy arising from the primary electron capture process is responsible of the fast M—CO bond breaking which prevents the trapping of 19-electron species M(CO) . Experimental and EHT-MO calculated g-tensors of the pentacoordinated anions are consistent with a square pyramidal C4ν structure having the unpaired electron in a molecular orbital with a high dz2 character
Electron spin resonance of γ-ray induced radicals in thiourea–adamantane solid solutions
No full textThiourea adducts of adamantane are shown to be suitable crystalline matrices for the selective preparation and e.s.r. study of radicals in combination with the γ-irradiation technique. Examples of applications to alcohols, ketones, and vinyl monomers are reported
ESR study of radical processes in irradiated DNA: the effect of the complexation with cis-dichloro diamino Pt(II)
No full textThe room temperature esr spectra of irradiated neat duplex hydrated, dehydrated and thermally denaturated DNA are interpreted in terms of the radicals formed by protonation of the thymine and cytosine anion radicals, by deprotonation of the guanine cation radicals, by addition of OH radicals at C8 of guanine and by loss of a methyl hydrogen from thymine. The complexation of DNA with cis-dichlorodiamino Pt(II) causes a drastic alteration of the radical distribution interpreted in terms of electron scavenging by the Pt(II) complex, a partial inhibition of the radical-cation chemistry of guanine, and enhancement of the reactivity of thymine toward hydrogen abstractions
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