scholarly journals Conserving Coherence and Storing Energy during Internal Conversion: Photoinduced Dynamics of cis- and trans-Azobenzene Radical Cations

2017 ◽  
Vol 121 (45) ◽  
pp. 8642-8651 ◽  
Author(s):  
Kristin Munkerup ◽  
Dmitri Romanov ◽  
Timothy Bohinski ◽  
Anne B. Stephansen ◽  
Robert J Levis ◽  
...  
Keyword(s):  
Internal Conversion ◽  
Radical Cations ◽  
Cis And Trans ◽  
Trans Azobenzene

ChemInform Abstract: CLATHRATION OF CIS- AND TRANS-AZOBENZENE BY THE COMPLEX NI(4-METHYLPYRIDINE)4(NCS)2

1973 ◽  
Vol 4 (41) ◽  
pp. no-no
Author(s):  
WIKTOR KEMULA ◽  
ZOFIA BORKOWSKA ◽  
DANUTA SYBILSKA
Keyword(s):  
Cis And Trans ◽  
Trans Azobenzene

The effect of meta- and para-methoxy substitution on the reactivity of the radical cations of arylalkenes and alkanes. Radical ions in photochemistry. Part 26

1991 ◽  
Vol 69 (5) ◽  
pp. 839-852 ◽  
Author(s):  
Donald R. Arnold ◽  
Xinyao Du ◽  
Kerstin M. Henseleit
Keyword(s):  
Electron Transfer ◽  
Radical Cation ◽  
Bond Cleavage ◽  
Cation Radical ◽  
Radical Cations ◽  
Addition Product ◽  
Molecular Orbital Calculations ◽  
Carbon Carbon Bond ◽  
Markovnikov Addition ◽  
Cis And Trans

The effect of meta- and para-methoxy substitution on the reactivity of some radical cations has been determined. The compounds chosen for study were 1-(3-methoxyphenyl)-1-phenylethylene (7), 1-(4-methoxyphenyl)-1-phenylethylene (8), 3-(3-methoxyphenyl)indene (9), 3-(4-methoxyphenyl)indene (10), methyl 2-(3-methoxyphenyl)-2-phenylethyl ether (11), methyl 2-(4-methoxyphenyl)-2-phenylethyl ether (12), cis- and trans-2-methoxy-1-(3-methoxyphenyl)indane (13), and cis- and trans-2-methoxy-1-(4-methoxyphenyl)indane (14). The radical cations of these compounds were generated by photosensitization (electron transfer) using 1,4-dicyanobenzene (3) as the electron acceptor. The three reactions studied were: (1) The addition of nucleophiles (methanol) to the radical cation of the arylalkenes, a reaction that yields the anti-Markovnikov addition product. (2) The carbon–carbon bond cleavage of radical cations, which yields products derived from the radical and carbocation fragments. (3) The deprotonation of the radical cation, a reaction that can be used to invert the configuration at a saturated carbon centre. The mechanisms of these reactions are discussed and the factors that need to be considered in order to predict reactivity are defined. Molecular orbital calculations (UHF/STO-3G) were carried out on the radical cations of the model compounds 3- and 4-vinylanisole and 3- and 4-methylanisole. Key words: photochemistry, photosensitize (electron transfer), radical cation, radical.

Reversible photochemical transformations of cis- and trans-2,3-dimethyloxirane radical cations in freonic matrices at 77K

2011 ◽  
Vol 21 (3) ◽  
pp. 153-154 ◽  
Author(s):  
Ivan D. Sorokin ◽  
Vladimir I. Feldman ◽  
Olga L. Melnikova ◽  
Vladimir I. Pergushov ◽  
Daniil A. Tyurin ◽  
...  
Keyword(s):  
Radical Cations ◽  
Photochemical Transformations ◽  
Cis And Trans

1,n-Radical ions. The photosensitized (electron transfer) formation of 1,5-radical cations

1987 ◽  
Vol 65 (12) ◽  
pp. 2734-2743 ◽  
Author(s):  
Donald R. Arnold ◽  
Brian J. Fahie ◽  
Laurie J. Lamont ◽  
Jacek Wierzchowski ◽  
Kent M. Young
Keyword(s):  
Electron Transfer ◽  
Radical Cation ◽  
Phenyl Ring ◽  
Bond Cleavage ◽  
Relative Rate ◽  
Radical Cations ◽  
Carbon Bond ◽  
Trans Isomerization ◽  
Carbon Carbon Bond ◽  
Cis And Trans

The photosensitized (electron transfer) reactions of 3-phenyl-2,3-dihydrobenzofuran (8a), 5-methyl-3-phenyl-2,3-dihydrobenzofuran (8b), cis and trans-2-methoxy-1-phenylindane (9, cis and trans), 3,3-diphenyltetrahydrofuran (10), and 2,2-diphenyl-1-methoxycyclopentane (11) have been studied using 1,4-dicyanobenzene as an electron-accepting photosensitizer and acetonitrile–methanol (3:1) as solvent. These reaction conditions cause carbon–carbon bond cleavage of analogous acyclic β,β-diphenylethyl ethers to give products derived from the diphenylmethyl radical and the α-oxycarbocation intermediates. The purpose of this study was to determine if this reaction could be applied to five-membered cyclic derivatives to give 1,5-radical cations.The primary products from 8a and 8b were the dehydrogenated, aromatized 3-phenylbenzofurans 14a and 14b. These products react further; continued irradiation gave the methanol adducts, cis and trans-2-methoxy-3-phenyl-2,3-dihydrobenzofuran (15a and 15b, cis and trans). The only observed reaction of the indanes (9, cis and trans) was cis-trans isomerization. Deuterium was incorporated at the bis-benzylic position of 8 and 9 when the irradiation was carried out in acetonitrilemethanol-O-d. These results are consistent with reversible deprotonation from the radical cations. There was no evidence for carbon–carbon bond cleavage with either 8 or 9. The relative rate, deprotonation faster than carbon–carbon bond cleavage, is explained in terms of the conformation of the bond that cleaves in relation to the singly occupied molecular orbital (SOMO) of the radical cation. Oxidation potential measurements support the conclusion that the SOMO of 8 and 9 is largely associated with the fused phenyl ring and is therefore orthogonal to the benzylic carbon–carbon bond. Irradiation of cis or trans-2-methoxy-3-phenyl-2,3-dihydrobenzofuran (15a, cis or trans), under these conditions, leads to cis–trans isomerization. The mechanism in this case involves the reversible loss of methanol. There is evidence that the addition of methanol to 14 involves the sensitizer radical anion – 14 radical cation pair.In contrast with the fused bicyclic systems, the monocyclic tetrahydrofuran 10 and the methoxycyclopentane 11 both cleave under these conditions; the products are the expected acetals 22 and 29 formed from the intermediate 1,5-radical cations. In 10 and 11 the SOMO, which is largely associated with the diphenylmethyl moiety, can overlap with the adjacent carbon–carbon bond and cleavage occurs as in analogous acyclic systems. Both 10 and 11 are relatively stable to irradiation under conditions that are identical except with acetonitrile as solvent (without methanol). We found no evidence for cyclization of the intermediates (1,5-radical cation or 1,5-diradical) into the terminal phenyl ring.

Carbon-13 and nitrogen-15 NMR spectra of cis- and trans-azobenzene, 4-monosubstituted and 4,4'-disubstituted trans-azobenzenes

1982 ◽  
Vol 47 (4) ◽  
pp. 1112-1120 ◽  
Author(s):  
Antonín Lyčka
Keyword(s):  
Nmr Spectra ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Downfield Shift ◽  
Signal Assignment ◽  
In Series ◽  
Characteristic Values ◽  
The Individual ◽  
Cis And Trans ◽  
Trans Azobenzene

13C and 15N NMR spectra of cis- and trans-azobenzene, 4-substituted trans-azobenzenes (N(CH3)2; NH2; OH; OCH3; CH3; Br; NO2) and 4,4'-disubstituted trans-azobenzenes (OH; NO2; NH2; OH; N(CH3)2, CH3; N(CH3)2, NO2) were measured. In comparison with trans-azobenzene, cis-azobenzene exhibits a downfield shift of nitrogen and C(1) signals and an upfield one of the C(2) and C(4) signals. The individual coupling constants nJ(15N13C) in 4-substituted and 4,4'-disubstituted trans-azobenzenes, respectively, have characteristic values and can be used for carbon signal assignment. With 4-substituted trans-azobenzenes, the 15N substitution chemical shifts of the nitrogen of the azo-bond were determined and their additivity in series of 4,4'-disubstituted trans-azobenzenes was proved.

Electronic states of cis- and trans-decalin radical cations in zeolites

1991 ◽  
Vol 187 (6) ◽  
pp. 565-570 ◽  
Author(s):  
Mary V. Barnabas ◽  
Alexander D. Trifunac
Keyword(s):  
Electronic States ◽  
Radical Cations ◽  
Cis And Trans

The effect of meta- or para-cyano substitution on the reactivity of the radical cations of arylalkenes and alkanes. Radical ions in photochemistry, Part 34

1995 ◽  
Vol 73 (3) ◽  
pp. 307-318 ◽  
Author(s):  
Donald R. Arnold ◽  
Xinyao Du ◽  
Jing Chen
Keyword(s):  
Electron Transfer ◽  
Molecular Orbital ◽  
Radical Cation ◽  
Radical Cations ◽  
Molecular Orbital Calculations ◽  
Single Electron Transfer ◽  
Radical Ions ◽  
Benzylic Carbon ◽  
Carbon Carbon Bond ◽  
Cis And Trans

The effect of electron-withdrawing substituents, meta- or para-cyano, on the reactivity of the radical cation of arylalkenes and alkanes has been determined. The radical cations were generated by single electron transfer (set) to an electron-accepting photosensitizer. Three reactions were studied: (i) the addition of nucleophile to the radical cation of arylalkenes, (ii) cleavage of the benzylic carbon–carbon bond of the radical cation of arylalkanes; and (iii) the deprotonation of the benzylic carbon–hydrogen bond of the radical cation of arylalkanes. The radical cations of 4-(1-phenylethenyl)benzonitrile (1b), 3-(1-phenylethenyl)benzonitrile (1c), 4-(2-methoxy-1-phenylethyl)benzonitrile (2b), 3-(2-methoxy-1-phenylethyl)benzonitrile (2c), cis- and trans-5-cyano-2-methoxy-1-phenylindane (6b-cis and -trans), and 6-cyano-3-phenylindene (7b) were generated, by single electron transfer to the lowest excited singlet state of 1,4-dicyanobenzene (3), in acetonitrile–methanol. The radical cations of 1b, 1c, and 7b react with methanol to yield the anti-Markovnikov adducts (2b, 2c, and 6b-cis and 6b-trans). The radical cations of 2b, 2c, and 6b-trans cleave at the benzylic carbon–carbon bond to give products derived from the radical and carbocation fragments. The radical cation of 6b-cis deprotonates from the benzylic position with subsequent formation of the diastereomer, 6b-trans. This behaviour can be explained/predicted on the basis of the proposed mechanisms for these reactions. Molecular orbital calculations (AM1) support the conclusions. Keywords: photosensitized, electron transfer, radical ions, radicals, molecular orbital calculations (AM1).

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