Germanium-centered Radicals Research Articles

Synthesis, Spectroscopic Behavior, and Photoinduced Reactivity of Tetraacylgermanes

Acylgermanes have been subject of great interest recently because of their low toxicity and the applicability as sources for germanium-centered radicals for visible-light induced free radical polymerization processes. We report on a novel and versatile method for the synthesis of tetraacylgermanes allowing the preparation of various tetra-substituted acylgermanes 1a–m. The formation of these derivatives was confirmed by NMR spectroscopy, mass spectrometry, and X-ray crystallography. UV–vis absorption spectra of the prepared compounds reveal absorption in the visible region. This transition was assigned by TD-DFT calculations. It enabled a general screening of the influence of different substitution patterns on the absorption properties. The radical formation upon irradiation was confirmed by TR-EPR spectroscopy.

The first direct observation of magnetic field effects on the dynamic behavior of radical pairs involving Group 14 silicon and germanium centered radicals

Laser flash photolysis was performed on micellar solutions and oil emulsions of organosilicon and organogermanium compounds ((aryl) n Me n-4 E: E=Si or Ge) in the absence and presence of magneticfields at room temperature. The dynamic behavior of the silyl and germyl radicals formed upon decomposition of the triplet states was directly observed. The lifetime of the radical pair of group 14 element centered and aryl radicals and the yields of the escaped silyl and germyl radicals were observed to increase with magnetic field strength increasing from 0 to 1.35 T

Etude de la réaction de germyllithiums sur la di-t-butyl-3,5 orthoquinone: mise en évidence d'un mécanisme par transfert monoélectronique

Reactions between organogermyllithiums R 3GeLi and 3,5-di-t-butylorthoquinone mainly give digermanes but also O-germylcatechol and germadioxolanes. It appears that these reactions start after an initial single electron transfer (SET) which is supported by an ESR study of the reaction. ESR analysis shows the transient formation of an O-semiquinonic species and also germanium centered radicals R 3Ge · (stable at 20°C for R = Mes). The digermane formation can occur through germanium centered radicals duplication. But it appears that other by-reactions lead also to digermane as O-germylcatechol lithiogermolysis and unexpected successive SET reactions. All these reactions which work to form digermanes are highly dependent on the nature of the R group linked to germanium and specially on their steric hindrance.

Polygermanes precurseurs d'especes du germanium a coordinance non usuelle

Several thermal or photochemical α-elimination reactions of functional polygermanes lead to germylenes, R 2Ge. Photolysis of polygermanes, cyclopolygermanes and polygermylmercury compounds and also hydrogen abstraction from various organohydropolygermanes using t-BuO ., lead to the formation of polymetallated chains containing one or two germanium-centered radicals. These polygermyl radicals give germylenes, R 2Ge, germanium centered radicals ▪, α-digermyl diradicals (or digermenes) [ ▪ or ▪] and β- or γ-polygermyl diradicals via a homolytic monoelectronic α-elimination process. In some cases the formation of α-digermyl diradicals or digermenes can also be seen as occurring through dimerization of germylenes but with lower yields. All these intermediates have been characterized by several trapping reactions with dimethyl disulfide, 2,3-dimethylbutadiene or biacetyl.

Synthese de composes a liaison M IVBmercure. Precurseurs d'especes monovalentes (germynes), et bivalentes (germylenes), de radicaux centrometalles et d'intermediaires

Polynuclear germylmercury compounds are obtained from the reaction of organohydrogermanes Ph n GeH 4− n or digermanes Ph 2 n Ge 2H 4− n ( n = 1, 2) with dialkylmercury R 2Hg. Di- or tri-mercurated geminal polygermates thus synthesized generally present a low stability and undergo thermal- or photo-decompositions leading to the corresponding monovalent (germynes), divalent (germylenes) or, trivalent (germanium centered radicals) species and also to intermediate ▪ biradicals which could be considered as limit forms of germanium doubly-bonded compounds ▪. Such intermediates have been chemically and spectroscopically characterized. Extension of these reactions to the silicon analogs met with difficulties, and thus previously observed differences between silicon and germanium chemistry were confirmed.

ChemInform Abstract: GERMANIUM‐CENTERED RADICALS. II. ELECTRON PARAMAGNETIC RESONANCE OF IRRADIATED SINGLE CRYSTALS OF HEXAPHENYLDIGERMOXANE

Chemischer InformationsdienstVolume 8, Issue 5 Physical Organic Chemistry ChemInform Abstract: GERMANIUM-CENTERED RADICALS. II. ELECTRON PARAMAGNETIC RESONANCE OF IRRADIATED SINGLE CRYSTALS OF HEXAPHENYLDIGERMOXANE M. GEOFFROY, M. GEOFFROYSearch for more papers by this authorL. GINET, L. GINETSearch for more papers by this author M. GEOFFROY, M. GEOFFROYSearch for more papers by this authorL. GINET, L. GINETSearch for more papers by this author First published: February 1, 1977 https://doi.org/10.1002/chin.197705056AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume8, Issue5February 1, 1977 RelatedInformation