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Journal articles on the topic '4-biradical'

Author: Grafiati

Published: 5 June 2025

Last updated: 1 August 2025

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1

Hastings, David J., and Alan C. Weedon. "Stereochemical studies of the photochemical cycloaddition reaction of alkenes with N-benzoylindole and N-carboethoxyindole; evidence for biradical intermediacy." Canadian Journal of Chemistry 69, no. 7 (1991): 1171–81. http://dx.doi.org/10.1139/v91-175.

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The stereochemistries of the 2 + 2 cycloaddition products obtained from the photochemical addition reaction between N-benzoylindole or N-carboethoxyindole and the alkenes cyclopentene, cyclohexene, cycloheptene, cis- and trans-2-butene, and cis- and trans-4-octene are examined. The structures of the products are shown to be consistent with a photo-cycloaddition mechanism involving the intermediacy of triplet 1,4-biradical species. The quantum yields of adduct formation between N-benzoylindole and both cis- and trans-octene were measured as a function of alkene concentration. The results sugges

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2

Meyer, Lars, and Paul Margaretha. "Biradical to biradical rearrangement via 1,3-H atom transfer in photocycloisomerizations of 4-pent-4-enylcyclohex-2-enones." Photochemical & Photobiological Sciences 3, no. 7 (2004): 684. http://dx.doi.org/10.1039/b403724c.

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3

Zhou, Yan, Junfang Xie, Chaoyi Jin, Yue Ma, and Licun Li. "Magnetic Relaxation in a Heterolanthanide Binuclear Complex Involving a Nitronyl Nitroxide Biradical." Magnetochemistry 11, no. 4 (2025): 26. https://doi.org/10.3390/magnetochemistry11040026.

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The reaction of nitronyl nitroxide biradical NITPhMeImbis(5-(2-methylimidazole)-1,3-bis(1′-oxyl-3′-oxido-4′,4′,5′,5′-tetramethyl-4,5-hydro-1H-imidazol-2-yl)-benzene) with Dy(hfac)3 and La(hfac)3 (hfac = hexafluoroacetylacetonate) afforded a heterolanthanide complex [Dy0.56La1.44(hfac)7(NITPhMeImbisH)] (1). In this complex, the biradical NITPhMeImbis ligand chelates one Ln(III) ion via its two neighboring NO units and simultaneously binds the La(III) ion through another NO group to form a dinuclear structure. Direct current (dc) magnetic measurement shows the dominant ferromagnetic couplings in

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4

Xi, Lu, Jing Han, Xiaohui Huang, and Licun Li. "Nitronyl Nitroxide Biradical-Based Binuclear Lanthanide Complexes: Structure and Magnetic Properties." Magnetochemistry 6, no. 4 (2020): 48. http://dx.doi.org/10.3390/magnetochemistry6040048.

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Employing a new nitronyl nitroxide biradical NITPhPzbis(NITPhPzbis = 5-(1-pyrazolyl)-1,3-bis(1’-oxyl-3’-oxido-4’,4’,5’,5’-tetramethyl-4,5-hydro-1H-imidazol-2-yl)benzene), a series of 2p-4f complexes [Ln2(hfac)6(H2O)(NITPhPzbis)] (LnIII = Gd1, Tb2, Dy3; hfac = hexafluoroacetylacetonate) were successfully synthesized. In complexes 1–3, the designed biradical NITPhPzbis coordinates with two LnIII ions in chelating and bridging modes to form a four-spin binuclear structure. Direct-current magnetic study of Gd analogue indicates that ferromagnetic exchange exists between the Gd ion and the radical

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5

Ito, Saki, Toru Yoshitake, and Takayuki Ishida. "Ferromagnetic 2p-2p and 4f-2p Couplings in a Macrocycle from Two Biradicals and Two Gadolinium(III) Ions." Molecules 27, no. 15 (2022): 4930. http://dx.doi.org/10.3390/molecules27154930.

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A new ground triplet biradical 2′,4′,6′-triisopropylbiphenyl-3,5-diyl bis(tert-butyl nitroxide) (iPr3BPBN) was prepared and characterized by means of room-temperature ESR spectroscopy displaying a zero-field splitting pattern together with a half-field signal. Complex formation with gadolinium(III) 1,1,1,5,5,5-hexafluoropentane-2,4-dionate (hfac) afforded a macrocycle [{Gd(hfac)3(μ-iPr3BPBN)}2]. As the X-ray crystallographic analysis clarified, the biradical serves as a bridging ligand, giving a 16-membered ring, where each nitroxide radical oxygen atom is directly bonded to a Gd3+ ion. The ma

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6

Wang, Xiao-Tong, Xiao-Hui Huang, Hong-Wei Song, Yue Ma, Li-Cun Li, and Jean-Pascal Sutter. "Cyclic [Cu-biRadical]2 Secondary Building Unit in 2p-3d and 2p-3d-4f Complexes: Crystal Structure and Magnetic Properties." Molecules 28, no. 6 (2023): 2514. http://dx.doi.org/10.3390/molecules28062514.

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Employing the new nitronyl nitroxide biradical ligand biNIT-3Py-5-Ph (2-(5-phenyl-3-pyridyl)-bis(4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide)), a 16-spin Cu-radical complex, [Cu8(biNIT-3Py-5-Ph)4(hfac)16] 1, and three 2p-3d-4f chain complexes, {[Ln(hfac)3][Cu(hfac)2]2(biNIT-3Py-5-Ph)2}n (LnⅢ= Gd 2, Tb 3, Dy 4; hfac = hexafluoroacetylacetonate), have been prepared and characterized. X-ray crystallographic analysis revealed in all derivatives a common cyclic [Cu-biNIT]2 secondary building unit in which two bi-NIT-3Py-5-Ph biradical ligands and two CuII ions are associated via the pyridine N at

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7

Kostryukov, S. G., E. V. Kraynov, A. Sh Kozlov, and O. Yu Chernyaeva. "SYNTHESIS OF REDOX-ACTIVE POLYMER BASED VERDASIL BIRADICAL." Вестник Пермского университета. Серия «Химия» = Bulletin of Perm University. CHEMISTRY 9, no. 3 (2019): 266–78. http://dx.doi.org/10.17072/2223-1838-2019-3-266-278.

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A redox-active polymer based on a verdazyl biradical - 4,4'-bis(3-(4’-hydroxyphenyl)-5-phenylverdazyl-1)-1,1'-biphenyl and 2,4-toluene diisocyanate was obtained. Verdazyl radical, being a diatomic phenol, easily reacts with toluene diisocyanate to form polyurethane. The presence of ure-thane bonds in the polymer molecule was confirmed by IR, and the presence of radical centers by EPR spectroscopy. The cyclic voltammetry method showed the ability of a polymer to undergo reversible redox transitions.

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8

Surinder, Berar, Berar UrmiJa, Thakur Mandeep, C. Gupta Satish, and C. Kamboj Ramesh. "Photochemistry of 3-alkoxy chromones : Photocyclisation of 3-benzyloxy-6-chloro-2-(1' -methyl-2' -phenylvinyl)-4-oxo-4H-1-benzopyran." Journal of Indian Chemical Society Vol. 85, July 2008 (2008): 759–62. https://doi.org/10.5281/zenodo.5817225.

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Department of Chemistry, Kurukshetra University, Kurukshetra-136 119, Haryana, India E-mail : rckamboj@rediffmail.com            Fax: 91-1744-238277 Manuscript received 31 December 2007. accepted 6 May 2008 Photocyclisation of 3-benzyloxy-6-chloro-2-(11 -methyl-21 -phenylvinyl)-4-oxo-4<em>H</em>-1-benzopyran with pyrex filtered <strong>UV</strong> light to yield linear tricyclic pyranopyrone and angular fused tetracyclic compound is described. The product formation occurred via cyclisation of 1,4-biradical produced through H-abstraction by <strong>C=O</strong> gro

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9

Cindro, Nikola, Margareta Horvat, Kata Mlinarić-Majerski, Axel G. Griesbeck, and Nikola Basarić. "Photoinduced homolytic C–H activation in N-(4-homoadamantyl)phthalimide." Beilstein Journal of Organic Chemistry 7 (March 2, 2011): 270–77. http://dx.doi.org/10.3762/bjoc.7.36.

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N-(4-homoadamantyl)phthalimide (5) on excitation and population of the triplet excited state underwent intramolecular H-abstractions and gave products 6 and 7. The major product, exo-alcohol 6 was a result of the regioselective δ H-abstraction and the stereoselective cyclization of the 1,5-biradical. Minor products 7 were formed by photoinduced γ H-abstractions, followed by ring closure to azetidinols and ring enlargement to azepinediones. The observed selectivity to exo-alcohol 6 was explained by the conformation of 5 and the best orientation and the availability of the δ-H for the abstractio

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10

Sugiyama, Hiroshi, Tsuyoshi Fujiwara, and Isao Saito. "Activation of neocarzinostatin-chromophore by 4-hydroxythiophenol: Intramolecular radical trapping of biradical intermediate." Tetrahedron Letters 35, no. 47 (1994): 8825–28. http://dx.doi.org/10.1016/s0040-4039(00)78508-x.

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11

Kalnin’sh, K. K., and S. G. Semenov. "Excited biradical states in thermal dimerization of bicyclo[2.2.0]hex-1(4)-ene." Russian Journal of Applied Chemistry 82, no. 10 (2009): 1877–81. http://dx.doi.org/10.1134/s1070427209100255.

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12

Nazin, G. M., A. I. Kazakov, A. V. Nabatova, L. L. Fershtat, and A. A. Larin. "Dependence of the decomposition rate of furoxanes on the polarity of the solvent." Himičeskaâ fizika 43, no. 4 (2024): 37–42. http://dx.doi.org/10.31857/s0207401x24040053.

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The decomposition rates of diphenylfuroxane and a number of 4-nitro-3-alkyl-furoxanes in dilute solutions were measured by manometric and calorimetric methods. In no case, an increase in the reaction rate was detected with an increase in the polarity of the solvent, which corresponds to the absence of an increase in the dipole moment of the molecule during the formation of a transition state. Based on this result, a conclusion is made about the biradical mechanism of decomposition of uncondensed disubstituted furoxanes in solutions.

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13

Pagacz-Kostrzewa, Magdalena, Daria Bumażnik, Stéphane Coussan, and Magdalena Sałdyka. "Structure, Spectra and Photochemistry of 2-Amino-4-Methylthiazole: FTIR Matrix Isolation and Theoretical Studies." Molecules 27, no. 12 (2022): 3897. http://dx.doi.org/10.3390/molecules27123897.

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The structure, tautomerization pathways, vibrational spectra, and photochemistry of 2-amino-4-methylthiazole (AMT) molecule were studied by matrix isolation FTIR spectroscopy and DFT calculations undertaken at the B3LYP/6-311++G(3df,3pd) level of theory. The most stable tautomer with the five-membered ring stabilized by two double C=C and C=N bonds, was detected in argon matrices after deposition. When the AMT/Ar matrices were exposed to 265 nm selective irradiation, three main photoproducts, N-(1-sulfanylprop-1-en-2-yl)carbodiimide (fp1), N-(1-thioxopropan-2-yl)carbodiimide (fp2) and N-(2-met

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14

Hewgill, FR, and MC Pass. "The Oxidation of (±)-Reticuline as Studied by E.S.R Spectroscopy." Australian Journal of Chemistry 38, no. 3 (1985): 497. http://dx.doi.org/10.1071/ch9850497.

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E.s.r. spectra obtained by oxidation of reticuline and closely related compounds in a flow system with cerium(IV) show chiefly the aryloxy radical derived from the 1-benzyl c-ring. The 4′-ethoxy homologue of norreticuline shows both A- and C-ring radicals in roughly equal proportions. The mechanism of intramolecular coupling is discussed, and as no evidence was obtained for the occurrence of a radical substitution reaction it is concluded that radical pairing is more likely, although this apparently happens too quickly for observation of a biradical species.

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15

Gambarelli, Serge, Daniel Jaouen, André Rassat, Louis-Claude Brunel, and Claude Chachaty. "High-Field Electron Spin Resonance Study of a Nitroxide Biradical, 1,4-Bis(4‘,4‘-dimethyloxazolidin-N-oxyl)cyclohexane." Journal of Physical Chemistry 100, no. 23 (1996): 9605–9. http://dx.doi.org/10.1021/jp953788u.

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16

Sato, K., T. Sawai, D. Shiomi, et al. "A cw/pulsed ESR study of a calix[4]arene biradical with two nitroxides." Synthetic Metals 137, no. 1-3 (2003): 1197–98. http://dx.doi.org/10.1016/s0379-6779(02)00982-7.

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17

Kostryukov, Sergey G., Artur Sh Kozlov, Dmitry A. Krasnov, Veronika S. Tezikova, Yulia Yu Masterova, and Lyudmila A. Klimaeva. "SYNTHESIS OF 3,3´-(1,4-PHENYLENE)BIS(1-(4-R-PHENYL)-5-PHENYL-5,6-DIHYDRO-1,2,4,5-TETRAZINIUM) PERCHLORATES." IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 64, no. 5 (2021): 4–11. http://dx.doi.org/10.6060/ivkkt.20216405.6342.

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A series of 3,3'-(1,4-phenylene)bis(1-4-R-phenyl)-5-phenyl-5,6-dihydro-1,2,4,5-tetrazinium) perchlorates containing hydrogen, methyl, bromio, methoxy, acetyl and nitro groups (R = H, Me, Br, OMe, COMe, NO2) as substituents were obtained as a result of a three-stage synthesis from terephthalic aldehyde. The synthesis of tetrazinium salts was carried out by reaction of the corresponding formazans with formalin in the presence of perchloric acid in dioxane. Formazans were obtained by reaction of terephthalic aldehyde phenylhydrazone with arenediazonium tosylates in a mixture of DMF and pyridine.

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18

Guerin, B., and L. J. Johnston. "Laser flash photolysis studies of 2,4,6-trialkylphenyl ketones." Canadian Journal of Chemistry 67, no. 3 (1989): 473–80. http://dx.doi.org/10.1139/v89-074.

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2,4,6-Triisopropylbenzophenone (3), 2,4,6–trimethylbenzophenone (4), and 2,4,6-trimethylacetophenone (5) have been examined by laser flash photolysis. Relatively long-lived triplets compared to similar mono-alkyl substituted ketones have been observed for each (280 ns, >2 μs and 220 ns in acetronitrile for 3, 4 and 5, respectively). Photoenol intermediates with λmax 360 nm and 380 nm were also observed from ketones 3 and 5, respectively. Ketone 3 yielded a mixture of approximately equal amounts of Z and E enols in hexane. The Z enol had a lifetime of ~4 μs while the E enol did not decay app

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19

Fišera, Lubor, Vladimír Oremus, Ladislav Štibrányi, Hans-Joachim Timpe, and Alena Máťušová. "Photo-induced rearrangement of isoxazolines - A pathway to 2,4,5,8-tetrahydro-1,3-dioxa-5-azocine derivatives." Collection of Czechoslovak Chemical Communications 50, no. 9 (1985): 1982–93. http://dx.doi.org/10.1135/cccc19851982.

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4-R-Substituted-8-X-phenyl-3,5,10-trioxa-9-azabicyclo[3,5,0]dec-8-enes (X = H, 4-CH3, 4-OCH3, 4-Cl, 4-Br, 4-F, 3-NO2, 3-Cl, 3-Br) have been prepared by cycloaddition of substituted benzenenitriloxides with 2-R-substituted 1,3-dioxep-5-enes (R = H, CH3, C6H5). A mixture of the endo and exo adducts is formed, if R is CH3 or C6H5. Their irradiation produces high yields of the title compounds as the single products. High selectivity of the photo-rearrangement is due to resonance stabilization of the biradical with p electrons of the oxygen atom. The quantum yields of the photoreaction vary from 0.

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20

Klán, Petr, and Jaromír Literák. "Temperature Dependent Solvent Effects in Photochemistry of 1-Phenylpentan-1-ones." Collection of Czechoslovak Chemical Communications 64, no. 12 (1999): 2007–18. http://dx.doi.org/10.1135/cccc19992007.

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Temperature dependent solvent effects have been investigated on the Norrish Type II reaction of 1-phenylpentan-1-one and its p-methyl derivative. Efficiencies of the photoreaction were studied in terms of solvent polarity and base addition as a function of temperature. Such a small structure change as the p-methyl substitution in 1-phenylpentan-1-one altered the temperature dependent photoreactivity in presence of weak bases. The experimental results suggest that the hydrogen bonding between the Type II biradical intermediate OH group and the solvent is weaker for 1-(4-methylphenyl)pentan-1-on

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21

Palumbo, Fabrizio, Francisco Bosca, Isabel Maria Morera, Inmaculada Andreu, and Miguel A. Miranda. "Biradical vs singlet oxygen photogeneration in suprofen–cholesterol systems." Beilstein Journal of Organic Chemistry 12 (June 14, 2016): 1196–202. http://dx.doi.org/10.3762/bjoc.12.115.

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Cholesterol (Ch) is an important lipidic building block and a target for oxidative degradation, which can be induced via free radicals or singlet oxygen (1O2). Suprofen (SP) is a nonsteroidal anti-inflammatory drug that contains the 2-benzoylthiophene (BZT) chromophore and has a π,π* lowest triplet excited state. In the present work, dyads (S)- and (R)-SP-α-Ch (1 and 2), as well as (S)-SP-β-Ch (3) have been prepared from β- or α-Ch and SP to investigate the possible competition between photogeneration of biradicals and 1O2, the key mechanistic steps in Ch photooxidation. Steady-state irradiati

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22

Havlas, Zdeněk, Mojmír Kývala, and Josef Michl. "Spin-Orbit Coupling in Biradicals. 4. Zero-Field Splitting in Triplet Nitrenes, Phosphinidenes, and Arsinidenes." Collection of Czechoslovak Chemical Communications 68, no. 12 (2003): 2335–43. http://dx.doi.org/10.1135/cccc20032335.

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The spin dipole-spin dipole and spin-orbit coupling contributions to the zero-field splitting parameter D of CH3-N, CH3-P, CH3-As, SiH3-N, SiH3-P, and SiH3-As have been calculated from CAS(12,11)/cc-pVTZ wave functions and the Breit-Pauli Hamiltonian at T1 B3LYP/cc-pVTZ optimized geometries. The spin-orbit coupling contributions represent a minor correction for the nitrenes, and bring the value computed for methylnitrene from 1.66 to 1.84 cm-1, in good agreement with experiment (1.72 cm-1). They dominate the spin-spin terms by an order of magnitude in phosphinidenes and by more than two orders

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23

Fišera, Lubor, Vladimír Ondruš, and Hans-Joachim Timpe. "Derivatives of tetrahydro-2H-pyridine from photorearranged cycloadducts of nitrile oxides." Collection of Czechoslovak Chemical Communications 55, no. 2 (1990): 512–23. http://dx.doi.org/10.1135/cccc19900512.

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1,3-Dipolar cycloaddition of methoxycarbonylnitrile, furannitrile and substituted benzene nitrile oxides (X = 4-CH3, 4-OCH3, 3-OCH3, 4-Cl, 3-Cl, 2,4-diCl, 4-F) to dimethyl 7-(diphenylmethylene)bicyclo[2.2.1]hept-2-ene-5,6-dicarboxylate (XII) led exclusively to exo cycloadducts IV, on irradiation with a low-pressure mercury lamp afforded the required 4-substituted derivatives of dimethyl 2,2-diphenyl-5-formyl-3-azabicyclo[4.3.0]nona-4,9-diene-7,8-dicarboxylate (XI) as sole products. Selectivity of the photorearrangement of isoxazolines IV to enaminoaldehydes XI is due to a stabilization of the

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24

Nagaoka, Shin-ichi, Kazuo Mukai, and Umpei Nagashima. "Ab initio study on magnetic properties of 1,1′,5,5′-tetramethyl- 6,6′-dithioxo-3,3′-biverdazyl homo-biradical and 3-(2′6′-di-t-butyl-4′-phenoxyl)-1,5-dimethyl-6-thioxoverdazyl hetero-biradical." Journal of Molecular Structure: THEOCHEM 455, no. 2-3 (1998): 199–203. http://dx.doi.org/10.1016/s0166-1280(98)00118-3.

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25

Ramesh, C. Kamboj, Dinesh Kumar Pratibha, Sharma Geeta, et al. "Intramolecular cyclisation of photolabile thienylchromenones : synthesis of angular tetracyclic compounds." Journal of Indian Chemical Society Vol. 90, Apr 2013 (2013): 481–87. https://doi.org/10.5281/zenodo.5770350.

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Department of Chemistry, Kurukshetra University, Kurukshetra-136 119, Haryana, India <em>E-mail</em> : rckamboj@rediffmail.com    Fax: 91-1744-238277 <em>Manuscript received 12 May 2011, revised 20 March 2012, accepted 07 June 2012</em> Photo-irradiation of 3-alkoxy-2-(thiophen-2-yI)-4H-chromen-4-ones in methanol with Pyrex filtered UV-Iight lead to the formation of interesting angular tetracyclic compounds. In the present study, we demonstrate the formation and distribution of the photoproducts which depends upon the stability of <em>in situ</em> generated 1,4-biradicals (throu

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26

Pincock, J. A., S. Rifai, and R. Stefanova. "The photochemistry of the 4-cyanobenzoic acid esters of trans- and cis-2-phenylcyclohexanol." Canadian Journal of Chemistry 79, no. 1 (2001): 63–69. http://dx.doi.org/10.1139/v00-167.

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Irradiation of trans-2-phenylcyclohexyl 4-cyanobenzoate (4) in methanol results in formation of the 1-phenylcyclohexene and 4-cyanobenzoic acid as the major products. The mechanism proposed for this example of the Norrish Type II-like reaction, normally inefficient for the π,π* state of esters, begins with intramolecular electron transfer in the excited singlet state. The next step, intramolecular proton transfer, is highly exergonic as a result of the increased acidity of the benzylic hydrogen of the radical cation and the increased basicity of the carbonyl oxygen of the radical anion. The fi

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27

Gravel, D., R. Giasson, D. Blanchet, R. W. Yip, and D. K. Sharma. "Photochemistry of the o-nitrobenzyl system in solution: effects of distance and geometrical constraint on the hydrogen transfer mechanism in the excited state." Canadian Journal of Chemistry 69, no. 8 (1991): 1193–200. http://dx.doi.org/10.1139/v91-178.

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Two rigid nitrobenzene derivatives, 5-nitro-1,2,3,4-tetrahydro-1,4-methanonaphthalene (6), and 5-nitro-1,2,3,4-tetra-hydro-1,4-ethanonaphthalene (7), have been synthesized and studied by picosecond flash absorption spectroscopy, steady-state irradiation, and MMX molecular mechanics calculations. Transients with lifetimes of 770 and 410 ps have been detected and assigned to the excited triplet states of 6 and 7, respectively. Consistent with prediction, the o-quinonoid intermediate is not detected in the time domain between the laser excitation and the end of decay of the triplet state. Intramo

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28

Alawode, Olajide E., Colette Robinson, and Sundeep Rayat. "Clean Photodecomposition of 1-Methyl-4-phenyl-1H-tetrazole-5(4H)-thiones to Carbodiimides Proceeds via a Biradical." Journal of Organic Chemistry 76, no. 1 (2011): 216–22. http://dx.doi.org/10.1021/jo1019859.

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29

Bock, Hans, Andreas John, Zdenek Havlas, and Jan W. Bats. "The Triplet Biradical Tris(3,5-di-tert-butyl-4-oxophenylene)methane: Crystal Structure, and Spin and Charge Distribution." Angewandte Chemie International Edition in English 32, no. 3 (1993): 416–18. http://dx.doi.org/10.1002/anie.199304161.

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30

Mashkovtsev, Rudolf I., та Yuanming Pan. "Biradical states of oxygen-vacancy defects in α-quartz: centers $$ E_{2}^{\prime \prime } $$ and $$ E_{4}^{\prime \prime } $$". Physics and Chemistry of Minerals 38, № 8 (2011): 647–54. http://dx.doi.org/10.1007/s00269-011-0437-0.

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Miesen, Franciscus W. A. M., Hans C. M. Baeten, Harm A. Langermans, Leo H. Koole, and Henk A. Claessens. "Novel, intramolecular hydrogen-transfer and cyclo-addition photochemistry of cyclic 1,3-dienes." Canadian Journal of Chemistry 69, no. 10 (1991): 1554–62. http://dx.doi.org/10.1139/v91-230.

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With use of one- and two-dimensional NMR spectroscopy and deuterium labelling, the photochemistry of 9-endo-hydroxy-9-exo-vinyl-bicyclo[4.2.1]nonadiene (1) and the 9-exo-(11-dimethylvinyl)- (2) and 9-exo-ethyl- (3) analogues has been studied. Irradiation of 1–3 gave novel 8-membered ring systems 4–6 by a light-induced rearrangement process, in which the hydroxyl proton is transferred on one side of the molecule toward one of the termini of the endocyclic diene. This rearrangement process thus involves a formal hydrogen transfer, during which either H+ or H• may be transferred to a reactive die

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Pang, Xiaojuan, Chenghao Yang, Ningbo Zhang, and Chenwei Jiang. "Nonadiabatic Surface Hopping Dynamics of Photocatalytic Water Splitting Process with Heptazine–(H2O)4 Chromophore." International Journal of Molecular Sciences 26, no. 10 (2025): 4549. https://doi.org/10.3390/ijms26104549.

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Recent research on the use of heptazine-based polymeric carbon nitride materials as potential photocatalysts for hydrogen evolution has made significant progress. However, the impact of the water cluster’s size on the time-dependent photochemical mechanisms during the water splitting process of heptazine–water clusters remains largely unexplored. Here, we present a Landau–Zener trajectory surface hopping dynamics calculation for heptazine–(H2O)4 clusters at the ADC(2) level. The electron-driven proton transfer (EDPT) mechanism reaction from water to hydrogen-bonded heptazine–water clusters was

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33

Duque-Prata, Amilcar, Carlos Serpa, and Pedro J. S. B. Caridade. "Photochemistry of 1-Phenyl-4-Allyl-Tetrazol-5-One: A Theoretical Study Contribution towards Mechanism Elucidation." Applied Sciences 11, no. 9 (2021): 4045. http://dx.doi.org/10.3390/app11094045.

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The photodegradation mechanism of 1-phenyl-4-allyl-tetrazol-5-one has been studied using (time-dependent) density functional theory with the M06-HF, B3LYP, and PBE0 functionals and the VDZ basis set. All calculations have been carried out using the polarizable continuum model to simulate the solvent effects of methanol. The reaction pathway evolution on the triplet state has been characterised to validate a previously postulated experimental-based mechanism. The transition states and minimums have been initially located by local scanning in partial constrained optimisation, followed by a fully

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34

Naghipur, Ali, Krzysztof Reszka, J. William Lown, and Anne-Marie Sapse. "Benzoxathiete and related structures: experimental and quantum chemical studies." Canadian Journal of Chemistry 68, no. 11 (1990): 1950–60. http://dx.doi.org/10.1139/v90-300.

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The products, plausible intermediates, and their mechanisms of formation in the aprotic diazotization of 2-[(2-acetoxyethyl)-sulfinyl (and sulfonyl)]anilines with isoamyl nitrate have been investigated by experimental and quantum chemical methods. Oxidation of 1,2,3-benzthiadiazole with hydrogen peroxide in acetic acid affords 1,2,3-benzthiadiazole-1-oxide, 13. The thermal stability of 13 up to 135 °C, together with EPR evidence which disfavors an aryldiazenyl radical precursor, discount 13 as an intermediate in the formation of benzoxathiete 14 or its valence tautomer 17 during aprotic diazot

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35

Jiang, Yun-Bao, Xiu-Juan Wang, and Li Lin. "Fluorescent Probing of the Restriction by Aqueous Micelles of the Formation of the Photoinduced Biradical State P* of 4-(Dimethylamino)chalcone." Journal of Physical Chemistry 98, no. 47 (1994): 12367–72. http://dx.doi.org/10.1021/j100098a035.

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36

Shultz, David A., Andrew K. Boal, and Gary T. Farmer. "The Biradical, Bis(3,5-di-tert-butyl-4-phenoxyl)methyleneadamantane, Exhibits Matrix-Dependent EPR Spectra Suggesting Rotamer Bistability with Differential Exchange Coupling." Journal of the American Chemical Society 119, no. 16 (1997): 3846–47. http://dx.doi.org/10.1021/ja964330o.

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37

Sawai, Takatoshi, Kazunobu Sato, Daisuke Shiomi, et al. "Intramolecular Hydrogen Bonding in Calix[4]arene-Based Nitroxide Monoradical and Biradical as Studied by CW-ESR and Pulse-ESR HYSCORE Spectroscopy." Applied Magnetic Resonance 41, no. 2-4 (2011): 337–52. http://dx.doi.org/10.1007/s00723-011-0269-6.

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38

Grenda, Sabrina, Maxime Beau та Dominique Luneau. "Synthesis, Crystal Structure and Magnetic Properties of a Trinuclear Copper(II) Complex Based on P-Cresol-Substituted Bis(α-Nitronyl Nitroxide) Biradical". Molecules 27, № 10 (2022): 3218. http://dx.doi.org/10.3390/molecules27103218.

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Trinuclear copper(II) complex [CuII3(NIT2PhO)2Cl4] was synthesized with p-cresol-substituted bis(α-nitronyl nitroxide) biradical: 4-methyl-2,6-bis(1-oxyl-3-oxido-4,4,5,5-tetramethyl-2-imidazolin-2-yl)phenol (NIT2PhOH). The crystal structure of this heterospin complex was determined using single-crystal X-ray diffraction analysis and exhibits four unusual seven-membered metallocycles formed from the coordination of oxygen atoms of the N-O groups and of bridging phenoxo (µ-PhO−) moieties with copper(II) ions. The crystal structure analysis reveals an incipient agostic interaction between a squar

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39

Liu, Fengbo, Hakim Karoui, Antal Rockenbauer, Simin Liu, Olivier Ouari, and David Bardelang. "EPR Spectroscopy: A Powerful Tool to Analyze Supramolecular Host•Guest Complexes of Stable Radicals with Cucurbiturils." Molecules 25, no. 4 (2020): 776. http://dx.doi.org/10.3390/molecules25040776.

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Stable organic free radicals are increasingly studied compounds due to the multiple and unusual properties imparted by the single electron(s). However, being paramagnetic, classical methods such as NMR spectroscopy can hardly be used due to relaxation and line broadening effects. EPR spectroscopy is thus better suited to get information about the immediate surroundings of the single electrons. EPR has enabled obtaining useful data in the context of host•guest chemistry, and a classical example is reported here for the stable (2,2,6,6-tetramethyl-4-oxo-piperidin-1-yl)oxyl or 4-oxo-TEMPO nitroxi

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Luneau, Dominique, Christophe Stroh, Joan Cano, and Raymond Ziessel. "Synthesis, Structure, and Magnetism of a 1D Compound Engineered from a Biradical [5,5‘-Bis(3‘ ‘-oxide-1‘ ‘-oxyl-4‘ ‘,4‘ ‘,5‘ ‘,5‘ ‘-tetramethylimidazolin-2‘ ‘-yl)-2,2‘-bipyridine] and MnII(hfac)2." Inorganic Chemistry 44, no. 3 (2005): 633–37. http://dx.doi.org/10.1021/ic049007y.

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41

Gonzalez, C. M., and J. A. Pincock. "Steric effects in the phototransposition reactions of dialkylbenzenes." Canadian Journal of Chemistry 84, no. 1 (2006): 10–20. http://dx.doi.org/10.1139/v05-258.

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The photochemistry, photophysical properties, and temperature dependence (25 to +65 °C) of fluorescence by quantum yields and excited singlet state lifetimes in acetonitrile have been examined for three sets of dialkylbenzene derivatives: Set 1 ortho-xylene (10), tetralin (11), and indan (12); Set 2 2,3-dimethylbenzonitrile (9-23), 5-cyanotetralin (T-23), and 4-cyanoindan (I-23); and Set 3 3,4-dimethylbenzonitrile (9-34), 6-cyanotetralin (T-34), and 5-cyanoindan (I-34). Phototransposition reactions occur for 10, 9-23, 9-34, and T-34. Fitting of the temperature-dependent fluorescence dat

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42

Netto-Ferreira, J. C., and J. C. Scaiano. "Laser flash photolysis study of the photochemistry of ortho-benzoylbenzaldehyde." Canadian Journal of Chemistry 71, no. 8 (1993): 1209–15. http://dx.doi.org/10.1139/v93-156.

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Ketene-enols 4 and 5 have been generated by laser flash photolysis of ortho-benzoylbenzaldehyde (3) and kinetically and spectroscopically characterized. In benzene or acetonitrile, the E ketene-enol, 4, shows absorption at 340 and 400 nm and a lifetime in excess of 1 ms, whereas the Z ketene-enol, 5, shows maxima at 360 and 430 nm and a lifetime of only 1.5 μs. At shorter time scales we observed a weak absorption (λmax = 580 nm) tentatively assigned to biradical 6 with a lifetime of 140 ns. The E ketene-enol is readily quenched by oxygen, dienophiles, methanol, and water, with quenching rate c

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43

HASTINGS, D. J., and A. C. WEEDON. "ChemInform Abstract: The Origin of the Regioselectivity in the (2 + 2)Photochemical Cycloaddition Reactions of N-Benzoylindole with Alkenes: Trapping of 1, 4-Biradical Intermediates with Hydrogen Selenide." ChemInform 23, no. 19 (2010): no. http://dx.doi.org/10.1002/chin.199219101.

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44

Tzirakis, Manolis D., та Mariza N. Alberti. "On the mechanism of the [4+2] cycloaddition of 1Ο2 with 1,3-dienes: Identifying the putative biradical/dipolar intermediate by employing the gem-diphenylcyclopropyl group as a mechanistic probe". Arkivoc 2015, № 3 (2015): 83–100. http://dx.doi.org/10.3998/ark.5550190.0016.307.

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45

Shiomi, Daisuke, Masafumi Tamura, Hiroko Aruga Katori, et al. "Magnetic structure of the 4,4,4′,4′,5,5,5′,5′-octamethyl-2,2′-m-phenylenebis(4,5-dihydroimidazol-1-oxyl 3-oxide) biradical: quantum spin effect of S= 1 species associated with structural change." J. Mater. Chem. 4, no. 6 (1994): 915–20. http://dx.doi.org/10.1039/jm9940400915.

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46

BOCK, H., A. JOHN, Z. HAVLAS, and J. W. BATS. "ChemInform Abstract: Structures of Charge-Perturbed and Sterically Overcrowded Molecules. Part 25. The Triplet Biradical Tris(3,5-di-tert-butyl-4-oxophenylene) methane: Crystal Structure and Spin and Charge Distribution." ChemInform 24, no. 28 (2010): no. http://dx.doi.org/10.1002/chin.199328119.

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47

Leigh, William J., Rabah Boukherroub, Christine J. Bradaric, Christine C. Cserti, and Jennifer M. Schmeisser. "Steady state and time-resolved spectroscopic studies of the photochemistry of 1-arylsilacyclobutanes and the chemistry of 1-arylsilenes." Canadian Journal of Chemistry 77, no. 5-6 (1999): 1136–47. http://dx.doi.org/10.1139/v99-114.

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Direct photolysis of 1-phenylsilacyclobutane and 1-phenyl-, 1-(2-phenylethynyl)-, and 1-(4'-biphenylyl)-1-methylsilacyclobutane in hexane solution leads to the formation of ethylene and the corresponding 1-arylsilenes, which have been trapped by photolysis in the presence of methanol. Quantum yields for photolysis of the three methyl-substituted compounds have been determined to be 0.04, 0.26, and 0.29, respectively, using the photolysis of 1,1-diphenylsilacyclobutane Φsilene = 0.21) as the actinometer. The corresponding silenes have been detected by laser flash photolysis; they have lifetimes

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48

Wang, Qi, Yong Li, and Guo-shi Wu. "Synthesis and reversible thermo-induced conformational transitions of a stable nitroxide biradical based on calix[4]areneElectronic supplementary information (ESI) available: selected experimental details. See http://www.rsc.org/suppdata/cc/b2/b201010k/." Chemical Communications, no. 12 (May 14, 2002): 1268–69. http://dx.doi.org/10.1039/b201010k.

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49

Ramesh, C. Kamboj, Thakur Mandeep, Berar Surinder, Berar Urmila, N. Siddiqui Zeba, and C. Gupta Satish. "Photoinduced reactions : Phototransformations of 2-aryl-3-(methoxymethoxy)- chromones." Journal of Indian Chemical Society Vol. 86, Dec 2009 (2009): 1325–31. https://doi.org/10.5281/zenodo.5823971.

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Department of Chemistry, Kurukshetra University, Kurukshetra-136 119, Haryana, India <em>E-mail</em>: rckamboj@rediffmail.com Fax: 91-1744-238277 Department of Chemistry, Aligarh Muslim University, Aligarh-202 002, Uttar Pradesh, India <em>Manuscript received 15 December 2008, revised 9 June 2009, accepted 7 July 2009</em> Photochemical cycllsation of 3-methoxymethyl ethers of 3-hydroxychromones to angular tetracyclic dihydroand dehydrogenated compounds Is studied. The product formation is explained on the basis of type-II hydrogen abstraction by the excited C=O group.

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50

Kostryukov, S. G., A. A. Burtasov, A. V. Dolganov, et al. "Synthesis of tetrazinyl biradicals containing a <i>p</i>-phenylene fragment." Журнал общей химии 93, no. 4 (2023): 507–15. http://dx.doi.org/10.31857/s0044460x23040029.

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3,3′-(1,4-Phenylene)bis[1-(4-R-phenyl)-5-phenyl-5,6-dihydro-1,2,4,5-tetrazinium] perchlorates were transformed into stable tetrazinyl biradicals by the action of D-glucose in slightly alkaline medium (NH4OH) in the presence of air oxygen. The tetrazinyl biradicals were isolated in individual state and characterized by cyclic voltammetry, elemental analysis, IR, UV, EPR spectroscopy methods.

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