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New complex of low-valent germanium PhenoxAPGe (I) based on the redox-active ligand 2,4,6,8-tetra-tert-butylphenoxazin-1-one is synthesized and structurally characterized. Its versatile reactivity is demonstrated for the acid-base and redox transformations. The reaction of germylene I with Ni(COD)2 is found to result in the substitution of both cyclooctadiene molecules, coordination of four germylene fragments to zero-valent nickel, and formation of compound (PhenoxAPGe)4Ni (II). The reaction of compound I with [CpNi(CO)]2 in a toluene solution affords complex (PhenoxAPGe)2(NiCp)2 (III), being the substitution product of two carbonyl groups by two isolobal germylene fragments. The reaction with the one-electron oxidant (3,6-di-tert-butyl-2-methoxyphenoxyl radical) generates labile paramagnetic germylene IV characterized by EPR spectroscopy. Digermylene oxide V synthesized by the hydrolysis of the starting germylene Iin situ reacts with N-heterocyclic carbene and KC8 to form ionic derivatives VI and VII containing the Ge(II)–O–Ge(II) fragment. Germylene I is tested as a catalyst for the hydroboration of benzaldehyde. The molecular structures of the compounds are determined by X-ray diffraction (СIF files CCDC nos. 2117783 (I), 2124277 (II), 2125357 (III), and 2118393 (VII)). [ABSTRACT FROM AUTHOR]

New stannylene AdAPSn (I) based on 4,6-di-tert-butyl-N-adamantyl-o-aminophenol is synthesized and structurally characterized. Stannylene I in the crystalline state forms infinite chains due to intermolecular donor–acceptor Sn–N and metallophilic Sn···Sn interactions. The reactivities of compound I and earlier synthesized t-BuAPSn (II) are studied using their redox and acid–base reactions. Stannylenes I and II are inserted at the S–S bond of tetramethylthiuram disulfide to form the corresponding tin(IV) dithiocarbamate complexes. The reactions with soft one-electron oxidants involve the redox-active o-amidophenolate ligand and generate labile paramagnetic stannylenes studied by EPR spectroscopy. The presence of a lone electron pair at the low-valence tin atom is a reason for its basic properties, which is demonstrated for the reaction of compound I with nanocarbonyl iron. The structures of selected synthesized compounds are determined by X-ray diffraction analysis (СIF files CCDC nos. 1905419–1905421). [ABSTRACT FROM AUTHOR]

Quantum-chemical calculations {DFT(B3LYP)/6-311+G(d,p)} were performed for all possible tautomers (aromatic and nonaromatic) of neutral 2- and 4-aminopyridines and their oxidized and reduced forms. One-electron oxidation has no important effect on the tautomeric preference for 2-aminopyridine. The amine tautomer is favored. However, oxidation increases the stability of the imine NH tautomer, and its contribution in the tautomeric mixture cannot be neglected. In the case of 4-aminopyridine, one-electron oxidation increases the stability of both the amine and imine NH tautomers. Consequently, they possess very close energies. As major tautomers, they dictate the composition of the tautomeric mixture. The CH tautomers may be considered as very rare forms for both neutral and oxidized aminopyridines. A reverse situation takes place for the reduced forms of aminopyridines. One-electron reduction favors the C3 atom for the labile proton for both aminopyridines. This may partially explain the origin of the CH tautomers for the anionic states of nucleobases containing the exo NH group. [ABSTRACT FROM AUTHOR]

Quantum-chemical calculations were performed for all possible isomers of neutral aniline and its redox forms, and intramolecular proton-transfer (prototropy) accompanied by π-electron delocalization was analyzed. One-electron oxidation (PhNH - e → [PhNH]) has no important effect on tautomeric preferences. The enamine tautomer is preferred for oxidized aniline similarly as for the neutral molecule. Dramatical changes take place when proceeding from neutral to reduced aniline. One-electron reduction (PhNH + e → [PhNH]) favors the imine tautomer. Independently on the state of oxidation, π- and n-electrons are more delocalized for the enamine than imine tautomers. The change of the tautomeric preferences for reduced aniline may partially explain the origin of the CH tautomers for reduced nucleobases (cytosine, adenine, and guanine). [ABSTRACT FROM AUTHOR]

The competition between positions C1 and C3 in homoadamantane upon oxidation was studied both theoretically and experimentally. B3PW91 and MP2 calculations in the 6-31+G* basis were used to study the structure of the homoadamantane radical-cation and its complexes with acetonitrile. The reaction was found to proceed predominantly at the homoadamantane C1 position in the reaction with photoexcited 1,2,4,5-tetracyanobenzene. [ABSTRACT FROM AUTHOR]

Radical cations of 1,4-dialkoxybenzenes 1 and 2 and alkyl 1,4-dialkoxybenzenes 3–9 generated in oxidation of the parent donors by perfluorodi[1-(2-fluorosulfonyl)ethoxy]propionyl peroxide 10 at -40°C and pentafluorobenzoyl peroxide 11 at 15°C were observed by ESR. Radical cation 6+, generated in other oxidation systems, i.e., Ce(SO4)2/THF, NH4/OAc and (NH4)2S2O8/HOAc, has also been investigated. Based on ESR observation and products analysis, an electron-transfer mechanism of the oxidation reaction is proposed and the influencing factors on hyperfine splitting constants of the radical cations are discussed. [ABSTRACT FROM AUTHOR]

One-electron oxidation of N-4-desmethylwyosine (dYt), a derivative of rare tricyclic nucleoside wyosine with several oxidative radicals, has been studied by using pulse radiolysis. The transient spectra of the radicals dYt˙+ and dYt(-H)˙ and the p K a of the radical cation were measured. The rate constants of reactions of dYt with SO and CO radicals have been determined and related reaction mechanisms were discussed. [ABSTRACT FROM AUTHOR]

The chemical processes of tryptophan (Trp), tyrosine (Tyr) and a dipeptide Trp-Tyr, which are induced by UV radiation and one-electron oxidation of SO[sup .][sub 4][sup –], have been investigated in aqueous solution by KrF (248 nm) laser flash photolysis. On the basis of optical studies, the photoionization of Trp and Tyr produces the tryptophan indolyl radical and tyrosine phenoxyl radical, respectively, and these are different from the intermediates resulting from interaction of Trp and Tyr with SO[sup .][sub 4][sup –]. In the case of Trp, SO[sup .][sub 4][sup –] would attack the indole moiety to produce a C(2)-yl sulphate radical adduct, and Tyr is oxidized to produce mainly the corresponding one-electron oxidized radical, which deprotonates rapidly to form the phenoxyl radical in neutral solution, and a possible sulphate radical adduct. From transient absorption spectra of photoionization of Trp-Tyr, an intramolecular electron transfer, Trp/N[sup .]-Tyr → Trp-Tyr/O[sup .], has been observed, but there was no observation of the process of one-electron oxidation of Trp-Tyr by SO[sup .][sub 4][sup –]. [ABSTRACT FROM AUTHOR]

Stable molecular complexes of bis[tris(trifluoromethyl)germyl]mercury( II) Hg[(CF)Ge] ( 1) with o-quinones (3,6-di- tert-butylbenzoquinone-1,2 ( 2), 3,6-di- tert-butyl-4,5-dimethoxybenzoquinone-1,2 ( 3), and 1,4,5,7-tetra- tert-butyldibenzo[1,4]dioxin-2,3-dione ( 4)) have been synthesized and characterized by elemental analysis and IR and electronic absorption spectroscopies. Depending on the ratio between the starting reactants, the reactions of o-quinones with 1 gave complexes of the composition RHg · Q ( 5, 7, 9) or RHg · Q ( 6, 8, 10), where Q= 2 ( 5, 6), 3 ( 7, 8), 4 ( 9, 10); R=Ge(CF). According to the spectral data, the molecule of o-quinone in RHg · Q acts as a neutral ligand, whereas the second molecule of o-quinone in RHg · Q is not coordinated to 1. It has been found by ESR that thermolysis of polycrystalline samples of complexes 6 and 10 involves intermediate formation of radical pairs and finally yields paramagnetic o-semiquinone complexes, SQGe(CF), which are typical products of one-electron oxidation of Organometallic compounds by o-quinones. [ABSTRACT FROM AUTHOR]

The electrochemical behavior of rhodium sandwich complexes containing η-pentamethylcyclopentadiene or tetramethylfulvene fragments has been studied by cyclic voltammetry. The complexes undergo one-electron oxidation to give unstable 17-electron radical cations which are converted into rhodocenium salts as a result of elimination or uptake of hydrogen or C-C bond cleavage. [ABSTRACT FROM AUTHOR]

The one-electron oxidation of toluidine blue by specific oxidising radicals such as Cl, Tl(II), N, Br etc. has been studied by employing the pulse radiolysis technique. The Br radical was found to be less efficient in oxidising toluidine blue as compared to Cl., Tl and N. The semioxidised species exhibited only one pK indicating the presence of two conjugate acid-base forms whose spectral and kinetic features were evaluated. Reaction of OH radicals with the dye gave rise to a transient species which exhibited spectral and kinetic features different from that of the semioxidised species indicating that the mode of reaction of OH is different. [ABSTRACT FROM AUTHOR]

One-electron oxidation of thionine has been studied using specific oxidizing radicals such as ClTl(II) and N generated by pulse radiolysis of aqueous solutions. The semioxidized thionine exhibited three pK's indicating four conjugate acid-base forms. N radicals were found to be less efficient in oxidizing thionine as compared to Cl, Tl and Tl(OH). The rate constants for electron abstraction from thionine by Cl, Tl, Tl(OH), Tl(OH) and N were evaluated. The spectra of different protonated forms of semioxidized thionine and the extinction coefficients at λ are presented. Reaction of OH radicals with thionine gave transient products whose spectra and acid-base properties were different from those of semioxidized thionine. The rate constant for formation of the product transient agrees well with competition kinetic value for reaction of OH with thionine reported earlier. [ABSTRACT FROM AUTHOR]

The reaction of salts of 1- aci-nitroethane and 1- aci-nitrobutane with sodium azide and ammonium peroxodisulfate in the methylene chloride—water two-phase system affords 1-azido-1-nitroethane and 1-azido-1-nitrobutane, respectively. [ABSTRACT FROM AUTHOR]