Complexes of tertiary amines with hindered quinones

The generation of radical pairs by low-temperature photolysis of solutions of sterically hindered quinones in aliphatic amines has been studied by ESR. The process of stabilization of radical pairs is related to molecular complexes between amines and quinones in solution.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1736–1738, September, 1995.This work was financially supported by the Russian Foundation for Basic Research (Project No. 95-03-09233a).     

Photochemical reactions of some mono- and diketo derivatives of adamantane in various solvents

Adamantanes are photoactive in the presence of CCl₄ and CDCl₃. The mechanism of their photolysis, involving the formation of singlet or triplet excited donor-acceptor complexes has been suggested.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1833–1835, September, 1995.This work was partially financially supported by the Russian Foundation for Basic Research (Project No. 93-03-18102).     

Unusual photorearrangement of 1,7-disubstituted 7-azabenzonorbornadiene

1-(11-Benzoyl-11-azatricyclo[6.2.1.0^2,7]undeca-2,4,6,9-tetraen-1-yl)ethanone was synthesized by cycloaddition of 2-acetyl-N-benzoylpyrrole to benzyne. Direct photolysis of 1-(11-benzoyl-11-azatricyclo-[6.2.1.0^2,7]undeca-2,4,6,9-tetraen-1-yl)ethanone in benzene gave N-(4-acetylnaphthalen-1-yl)benzamide. The formation of this product is discussed in terms of radical-stabilizing and destabilizing effect of electron-withdrawing group in the formation of cyclopropane ring. Published in Russian in Zhurnal Organicheskoi Khimii, 2009, Vol. 45, No. 4, pp. 626–629. The text was submitted by the authors in English.     

Reagents for directed modification of biopolymers

The synthesis of new heterobifunctional reagents that are photo-activated, namely, 6-azido-1,3,4,5,7,8-hexafluoro-2-naphthoic acid (2), succinimido-6-azido-1,3,4,5,7,8-hexafluoro-2-naphthoate (3), andN-(n-butyl)-1,3,4,5,7,8-hexafluoro-2-naphthamide (4), which simulates the product of addition of acid2 to biopolymers, is described. The photolysis of azides2 and4 in methanol and pyridine was studied. Azide4 is superior to photoreagents based on perfluoroaromatic azides of the benzene series in spectral photosensitivity and rate of photolysis in the UV region (334–405 nm). When azide4 is irradiated with light at wavelengths above 400 nm, the rate of its photolysis in methanol increasesca. 10-fold in the presence of a singlet sensitizer, 9-aminoacridine, which makes reagent3 promising for designing binary systems sensitive to visible light. For Part 8, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 328–333, February, 1998.     

Determination of the gas-phase reactivity of hydroxyl with chlorinated methanes at high temperature: Effects of laser/thermal photochemistry

Atmospheric pressure absolute rate coefficients have been determined for the gas phase reaction of OH radicals with methyl chloride (k₁), methylene chloride (k₂), and chloroform (k₃) over an extended temperature range using a laser photolysis/laser-induced fluorescence technique. The rate coefficients are best described by the following modified Arrhenius equations: Measurements were obtained as a function of excimer photolysis intensity and are compared with previous results and extended to higher temperatures. Photolysis intensities in excess of 12 mJ-cm^?2 were found to measurably increase (up to a factor of 2) the rate coefficients for k₃ between 400–775 K, with the effect increasing with increasing temperature. A similar, yet much smaller (ca. 20–35%) increase was observed for k₂ between 675–955 K. No effect was observed for k₁ at any temperature. Relative absorption coefficient measurements at 193.3 nm indicated that chlorinated methane photolysis increases with both increasing temperature and increasing chlorine substitution. These measurements suggest that reactant photolysis may be responsible for the observed dependence of k₂ and k₃ on photolysis intensity at elevated temperatures. The puzzling and disconcerting discrepancy between previously published high temperature measurements of k₃ and transition state model predictions is reconciled with these latest measurements. © 1993 John Wiley & Sons, Inc.     

Synthesis and reactivity of germanium heterocycles containing germanium-tin bonds

Previously unknown stannyl-substituted germanium heterocycles, 1, 1 -bis(trimethylstannyl) 2,3,4,5-tetraphenyl-l-germacyclopenta-2,4-dienc and 1,1-bis(trimethylstannyl)-3,4-dimethyl-1-germacyclopent-3-ene were synthesized, and their photolysis and chemical transformations were Studied.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp 2764–2767, November, 1996.     

The synthesis and photochemistry of 4-amino-3-cyanopyrazole

4-Amino-3-cyanopyrazole ( 6 ) had once been considered to be a possible intermediate in the photochemical conversion at 350 nm of diaminomaleonitrile ( 1 ) into 4-amino-5-cyanoimidazole ( 3 ), a precursor of adenine. The pyrazole was synthesized and irradiated at 350 nm. No isomerization into the imidazole was observed, even when the photolysis was carried out in the presence of an excess of 1 , where sensitization by this or one of its photolysis products might have operated. At 254 nm, complete decomposition of 6 was observed, with formation of polymeric products. At 300 nm, 6 underwent isomerization to 3 , as well as extensive decomposition. Hydrogen cyanide was probably produced, which reacted with the remaining starting material to yield 7-aminopyrazolo[4,3-d]pyrimidine ( 10 ), which did not isomerize into adenine under the photolysis conditions. A polymer was also obtained, from which glycine was identified after hydrolysis.     

Photolysis of thallium azide

Preliminary treatment of TlN₃(A) with light (λ = 365 nm, I > 1 × 10¹⁴ quantum cm⁻² s⁻¹) in a vacuum (1 × 10⁻⁵ Pa) at 293 K led to the formation of a new long-wave region of spectral sensitivity. The products of photolysis of TlN₃(A) thallium and nitrogen formed in the stoichiometric ratio on the sample surface. The topography and kinetics of thallium accumulation were determined, and the effective rate constants for photolysis evaluated. Measurements of the contact voltage, current-voltage characteristics, and photocurrent showed that the photolysis of thallium azide resulted in the formation of TlN₃(A)-Tl (photolysis product) microheterogeneous systems. A model of photolysis of TlN₃(A) was suggested. According to this model, photolysis included the generation, recombination, and redistribution of nonequilibrium charge carriers in the contact field and the formation of the end products of photolysis. The limiting stage of photolysis of TlN₃(A) was the diffusion of interstitial thallium cations toward the neutral (T _n Tl _m )⁰ center. Original Russian Text ? E.P. Surovoi, L.I. Shurygina, L.N. Bugerko, N.V. Borisova, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 4, pp. 784–790.     

Isotope effect in the gas-phase photolysis of cyclohexanone

An isotope effect was found for the carbonyl and -carbon atom in the gasphase photolysis of cyclohexanone, which is apparently magnetic in nature. This finding additionally indicates that the chemically induced dynamic nuclear polarization in the gas phase in the photolysis of cyclohexanone arises predominantly in biradicals and not in triplet molecules. The separation of isotopes occurs more efficiently in the photolysis of aqueous solutions of cyclohexanone than in the gas phase.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2364–2365, October, 1989.     

Rearrangements photochimiques d'α-epoxycetones spiranniques et de composes dicarbonyles; nouvelle etude de la photolyse du benzoyloxy-3-5-cholestene-2; photoepimerisation en 5 de la benzoyl-2-5α-cholestanone-3

The photolysis of epoxides derived from 2 - benzylidène - 5α - cholestan - 3 - one depends considerably on stereochemistry. No photoepimerisation can be detected; expected β diketones are formed. Several tautomeric forms of 2 - benzoyl - 5α - cholestan - 3 - one have been isolated in crystalline form, and some exist in neutral solution. A δ hydrogen abstraction by the benzoyl group is involved in the photolysis of this δ-diketone.     

Photochemical isomerization of 2H-imidazoleN-oxides

1,3-Diaza-6-oxabicyclo[3.1.0]hex-3-enes and their 3-oxides were obtained by the photolysis of 2H-imidazole 1-oxides and 2H-imidazole 1,3-dioxides. 1,3-Diaza-6-oxabicyclo [3.1.0]hex-3-ene 3-oxides are thermally unstable and are converted to the starting 2H-imidazole 1,3-dioxides; their further photolysis affords a mixture of stereoisomeric 1,3-diaza-4,7-dioxatricyclo [4.1.0.0^3,5]heptanes.For the previous communication, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2096–2100, December, 1993.     

Absorption cross section and photolysis of OIO

Pulsed laser photolysis combined with transient absorption spectroscopy and resonance fluorescence was used to examine the photolysis of OIO at a number of wavelengths corresponding to absorption bands in its visible spectrum between approximately 530 and 570 nm. Photolysis at 532 nm was found to result in substantial depopulation of the absorbing ground state, enabling an estimate for the absorption cross section of OIO at 610.2 nm of (6 +/- 2) x 10(-18) cm2 molecule(-1) to be obtained. No evidence was found for I atom formation following photolysis of OIO at 532, 562.3, 567.9 and 573.8 nm, enabling an upper limit to the I atom quantum yield of < 0.05 (560-580 nm) and < 0.24 (532 nm) to be established.     

Photoinduced electron transfer in ion pairs of cation-anion polymethine dyes

Photoinduced electron transfer in ion pairs of cation-anion polymethine dyes was studied by flash photolysis. The formation of radicals, which are the products of photoinduced transfer of an electron from an anion to a cation in the ion pairs, was observed during photoexcitation of a number of cation-anion dyes in nonpolar and some weakly polar solvents (in particular, in toluene and chloroform). Photoinduced electron transfer is also observed during triplet sensitization of ion pairs of the cation-anion dyes. The redox potentials of the cations and anions constituting the dyes were measured; the radical yields were compared with the free energies of photoinduced electron transfer. Photoinduced electron transfer in the systems under study was compared with similar process in cyanineborate ion pairs.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 878–884, May, 1995.The authors thank I. Ya. Levitin for help in measuring redox potentials.This work was financially supported by the Russian Foundation for Basic Research (Project No. 93-03-4217).     

Photolysis of 2-dialkylamino-3-amino(or alkylamino)-1,4-naphthoquinones

Using¹H and¹³C NMR spectroscopy, naphthodihydroimidazolediols were identified as the primary products of photolysis of 2-dialkylamino-3-amino(alkylamino)-1,4-naphthoquinones. Their further non-photochemical (thermal) transformations depend on their structure and on the photolysis conditions.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 358–362, February, 1993.     

ESR study of the photolysis of C60Cl6

The photolysis of C₆₀Cl₆ in the presence of α-phenyl-N-tert-butylnitron (PBN) as a spin trap was studied by ESR spectroscopy. It was shown that a C−Cl bond undergoes homolytic cleavage to give a stable fullerenyl radical of the cyclopentadienyl type, whose formation was confirmed by quantum-chemical computations. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 752–754, April, 2000.     

Cis-trans-isomerization of cationic-anionic polymethine dyes

The effect of solvent polarity and ion pair formation oncis-trans-isomerization of cationic-anionic polymethine dyes and of related simple cationic and anionic dyes is studied by flash photolysis. The change in the rate constant for reversecis-trans- isomerization of photoisomers due to the interaction of a cation with an anion in an ion pair is observed in nonpolar solvents. A drop in the yield of the photoisomers to zero is observed for a number of cationic-anionic dyes in weakly polar and nonpolar solvents which is possibly due to steric hindrances in the photoisomerization process in ion pairs.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 719–724, April, 1993.     

Photolysis of 2,6 di-tert-butyl-4-tert-butylperoxy-4-methyl-2,5-cyclohexadienone

The photolysis of a heptane solution of 2,6-di-tert-butyl-4-tert-butylperoxy-4-methyl- 2,5-cyclohexadienone (1) with light of 360–480 nm in the presence of 2,6-di-tert-butyl-4-methylphenol or 2,4,6-tri-tert-butylphenol gives rise to their corresponding phenoxyls in a reaction with the tert-butoxyl arising in the photolysis. Direct evidence of the formation of t-BuO^. by the photolysis of 1 was provided by the ESR characterization of spin-adducts of this radical with nitrosobenzene and nitrosodurene. Evidence of the photolysis of the peroxide bond in 1 is important for the mechanism of reaction of phenolic chain-breaking antioxidants.     

Photochemical and thermal transformations of diazo derivatives of 1-aryloxy- and 1-arylthio-2-aminoanthraquinones

In the photochemical and thermal decomposition of diazonium derivatives of 1-aryloxy- and 1-arylthio-2-aminoanthraquinones in CH ₃ COOH and dioxane, high yields of intramolecular arylation products — anthra-[2, 1-d]-4-tert-butylbenzo-[b]-furan-and anthra-[2, 1-d]-4-tert-butylbenzo-[b]-thiophene-8,13-diones — are formed. It was established that 2-azo derivatives of 1-aryloxy- and 1-acyloxyanthraquinones synthesized on the basis of the diazonium salts are stable under photolysis conditions.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 582–585, March, 1992.     

Photochemical synthesis and properties of quintet pyridyl-2,6-dinitrenes

The structures and properties of quintet pyridyl-2,6-dinitrenes formed by low-temperature photolysis of 2,6-diazidopyridines were studied by ESR and quantum chemical (B3LYP/6-31G^*) methods. The synthesized dinitrenes represent a new type of quintet tetraradicals for which the ratio of zero-field splitting parameters is | E _q|/|D _q| = 1/3. This ratio is characteristic of quintet molecules in which the vector angle between two biradical centers is close to 114.5°. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1536–1540, September, 2006.     

Studies on Debenzylation and Photolysis of 1-Benzyl- and 1-(β-Phenethyl)-1,2,3,4-tetrahydroisoquinolines

Debenzylation of 1-(3-benzyloxybenzyl)-1,2,3,4-tetrahydroisoquinolines 1 , 6 , 7 with hydrochloric acid and ethanol gave the corresponding phenolic isoquinolines 2 , 8 , 9 and tetrahydroprotoberberines 4 , 12 , 13 . Compounds 2 , 8 , 9 on photolysis also gave, besides the expected noraporphines 3 , 10 , 11 , the tetrahydroprotoberberines 4 , 12 , 13 [1–4] (Schemes 1 and 2). 6-Benzyloxy-1-(5-benzyloxy-2-bromo-benzyl)-1,2,3,4-tetrahydroisoquinoline (27a) containing no methoxy or methylenedioxy groups either in ring A or C does not give protoberberine during debenzylation; but 28 , the debenzylation product of 27a , on photolysis gives both the noraporphine 29 and the tetrahydroprotoberberine 30 (Scheme 6), proving that during debenzylation of 1-(3-benzyloxybenzyl)-1,2,3,4-tetrahydroisoquinolines containing additional methoxy or methylenedioxy groups, the necessary formaldehyde comes from the latter groups. During photolysis both the methoxy groups (methylenedioxy groups) and the C(3) atom of the tetrahydroisoquinoline moiety provide the formaldehyde. Veratrole under debenzylation and photolytic conditions and tetrahydroisoquinoline under the latter condition also give rise to formaldehyde (Schemes 8 and 10). The novel bromohomoprotoberberine 43 along with 42 was formed during debenzylation of the 1-phenethyl-1,2,3,4-tetrahydroisoquinoline 41 . Photolysis of 42 yielded the novel nor-homoaporphine 44 , in addition to 43 ; the latter was debrominated to give the homoberbine 45 .