Journal of Photochemistry最新文献

{"title":"Photophysics of photoconducting polymers with pendant bichromophores I: Intramolecular photoprocesses in 9-[γ-(N-carbazolyl)propyl]-9-methyl-2,7-dinitrofluorene","authors":"Bogumil Zelent,&nbsp;Philippe Messier,&nbsp;Denis Gravel,&nbsp;Sylvain Gauthier,&nbsp;Gilles Durocher","doi":"10.1016/0047-2670(87)87052-1","DOIUrl":"10.1016/0047-2670(87)87052-1","url":null,"abstract":"<div><p>Electronic absorption and luminescence spectroscopies were used to study the intramolecular photoprocesses in the bichromophoric D—A compound 9-[γ-(<em>N</em>-carbazolyl)propyl]-9-methyl-2,7-dinitrofluorene (<strong>II</strong>) together with the monochromophoric model molecules <em>N</em>-ethylcarbazole (NEC) and 9-γ-hydroxypropyl-9-methyl-2,7-dinitrofluorene (<strong>I</strong>). It was shown that no intramolecular charge transfer interaction exists between the carbazolyl and the 2,7-dinitrofluorene chromophores in the electronic ground state of the bichromophoric compound <strong>II</strong> in EPA at room temperature and at 77 K. In contrast, the strong quenching effect of the fluorescence and phosphorescence emission of the carbazolyl chromophore in the bichromophoric molecule <strong>II</strong> was explained in terms of intramolecular energy transfer and the possible electron transfer interactions between the carbazolyl and the 2,7-dinitrofluorene groups. These two intramolecular photoprocesses in <strong>II</strong> were characterized well by the Förster critical transfer distance (<em>R</em>₀ = 2.6 Å at 296 K and <em>R</em>₀ = 30.4 Å at 77 K) and by the Rehm-Weller free energy change of the electron transfer step (Δ<em>G</em>_ET &lt; 0) respectively. Electron transfer processes are usually facilitated by good orbital overlap, but this is not favored by the spatial conformation of the chromophores in <strong>II</strong>. This is in agreement with the fact that the phosphorescence lifetime (τ_P = 0.12 ± 0.01) and the phosphorescence quantum yield (φ_P = 0.060 ± 0.006) of the monochromophoric molecule <strong>I</strong> remain the same in <strong>II</strong> and in the polymer (<strong>III</strong>) (polysebacate containing <strong>II</strong> as a pendant group). We concluded that long-range energy transfer (Förster type) seems to be the dominant path in these systems.</p></div>","PeriodicalId":16771,"journal":{"name":"Journal of Photochemistry","volume":"40 1","pages":"Pages 145-168"},"PeriodicalIF":0.0,"publicationDate":"1987-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0047-2670(87)87052-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80163230","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An examination of diffusion-influenced fluorescence quenching by nearest quenching neighbors in liquids","authors":"B. Stevens, D. N. McKeithan","doi":"10.1016/0047-2670(87)87039-9","DOIUrl":"https://doi.org/10.1016/0047-2670(87)87039-9","url":null,"abstract":"","PeriodicalId":16771,"journal":{"name":"Journal of Photochemistry","volume":"36 1","pages":"1-8"},"PeriodicalIF":0.0,"publicationDate":"1987-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82204926","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Announcement: the Grammaticakis-Neumann award in photochemistry","authors":"A.M. Braun","doi":"10.1016/0047-2670(87)87057-0","DOIUrl":"10.1016/0047-2670(87)87057-0","url":null,"abstract":"","PeriodicalId":16771,"journal":{"name":"Journal of Photochemistry","volume":"40 1","pages":"Page 193"},"PeriodicalIF":0.0,"publicationDate":"1987-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0047-2670(87)87057-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90841925","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Formation and decay of nitronic acid in the photorearrangement of o-nitrobenzyl esters","authors":"Q.Q. Zhu,&nbsp;W. Schnabel,&nbsp;H. Schupp","doi":"10.1016/0047-2670(87)80041-2","DOIUrl":"10.1016/0047-2670(87)80041-2","url":null,"abstract":"<div><p><em>o</em>-Nitrobenzyl benzoate (oNBB), α-methyl-<em>o</em>-nitrobenzyl benzoate (αMoNBB), α-phenyl-<em>o</em>-nitrobenzyl benzoate (αPoNBB) and copolymers of methyl methacrylate and of <em>o</em>-nitrobenzyl, methyl-<em>o</em>-nitrobenzyl and phenyl-<em>o</em>-nitrobenzyl acrylates were flash photolysed or continuously irradiated with UV light in dilute solution. The quantum yield φ(PR) of bond cleavage in the photorearrangement of the <em>o</em>-nitrobenzyl esters does not depend on the chemical nature of the ester group but is significantly influenced by the substituent in the α position φ(PR) = 0.22 ± 0.03 (αMoNBB, αPoNBB) and φ = 0.10 ± 0.02 (oNBB). This was revealed from the yields of carboxylic acid and <em>o</em>-nitrobenzyl groups. The differences in φ(PR) correspond to the differences in the yields of nitronic acid formed as an intermediate. In aqueous systems the kinetics of the decay of the nitronic acid were found to be determined by the formation of rather stable nitronate ions according to the equilibrium <figure><img></figure> The relatively long lifetime of the nitronate ion formed in the case of oNBB (longer than 100 ms) is assumed to be caused by a rather strong intramolecular interaction of the hydrogen at the α-carbon with the nitronate group and the carbonyl group. In acetonitrile solution, where nitronate ions were not formed, the non-substituted compound (oNBB) also behaved differently from the substituted compounds (αMoNBB and αPoNBB): two transients differing in lifetime (6 × 10⁻⁴ and 5.8 × 10⁻³ s) were observed with oNBB which were ascribed to different isomers of the nitronic acid. Addition of H₂SO₄ to acetonitrile solutions accelerated the rearrangement of the nitronic acid. The acceleration is assumed to be caused by protonation of the oxygen of the carbonyl group. The carbocation formed this way strongly interacts intramolecularly with oxygens of the nitronic acid group, thus inducing the rearrangement.</p></div>","PeriodicalId":16771,"journal":{"name":"Journal of Photochemistry","volume":"39 2","pages":"Pages 317-332"},"PeriodicalIF":0.0,"publicationDate":"1987-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0047-2670(87)80041-2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83766046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A theoretical study of two-color photoionization and autoionization of molecules","authors":"S.H. Lin,&nbsp;A. Boeglin,&nbsp;S.M. Lin","doi":"10.1016/0047-2670(87)80031-X","DOIUrl":"10.1016/0047-2670(87)80031-X","url":null,"abstract":"<div><p>The main purpose of this paper is to apply the density matrix formalism for treating multiphoton ionization of multirovibronic level systems. Both direct photoionization and photoionization through autoionization states are taken into account. Numerical results will be presented for demonstrating the effect of the interference resulting from the neighboring rovibronic levels. The theoretical results are applied to interpret two sets of experimental data on two-color photoionization of molecules; one set is for two-color threshold photoionization spectra of jet-cooled aniline which exhibit autoionizing Rydberg structures and the other is for high resolution Rydberg spectra of H₂ by stepwise resonance two-photon ion-pair (H⁺ + H⁻) production.</p></div>","PeriodicalId":16771,"journal":{"name":"Journal of Photochemistry","volume":"39 2","pages":"Pages 173-200"},"PeriodicalIF":0.0,"publicationDate":"1987-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0047-2670(87)80031-X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78290800","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The effect of added salts on electron transfer reactions involving exciplexes: the N,N-dimethylaniline-photosensitized dechlorination of 4-chlorobiphenyl","authors":"C.A. Chesta,&nbsp;J.J. Cosa,&nbsp;C.M. Previtali","doi":"10.1016/0047-2670(87)80036-9","DOIUrl":"10.1016/0047-2670(87)80036-9","url":null,"abstract":"<div><p>The dechlorination of 4-chlorobiphenyl (ClBi) photosensitized by <em>N,N</em>-dimenthylaniline (DMA) was studied in methanolic and ethyl acetate solutions by means of continuous photolysis at 313 nm. The hydrogen chloride quantum yield was measured as a function of ClBi concentration. The reaction proceeds mainly via DMA singlet state sensitization.</p><p>Excited singlet deactivation of DMA by ClBi was investigated by fluorescence quenching. In low polarity solvents such as cyclohexane and ethyl acetate, the fluorescence quenching was accompanied by the appearance of the fluorescence band of an exciplex. The fluorescence quenching of the DMAClBi exciplex by tetrabutylammonium perchlorate and lithium perchlorate was also studied. Both salts enhanced the sensitized dechlorination of ClBi and an electrostatic interaction between undissociated perchlorates and the exciplexes is postulated to be responsible for the enhanced dechlorination.</p></div>","PeriodicalId":16771,"journal":{"name":"Journal of Photochemistry","volume":"39 2","pages":"Pages 251-261"},"PeriodicalIF":0.0,"publicationDate":"1987-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0047-2670(87)80036-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91494826","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fluorescence and phosphorescence of harmol and harmalol at 77 K","authors":"A. Olba,&nbsp;P. Medina,&nbsp;A. Codonñer,&nbsp;S. Monsó","doi":"10.1016/0047-2670(87)80038-2","DOIUrl":"10.1016/0047-2670(87)80038-2","url":null,"abstract":"<div><p>We have investigated the fluorescence and phosphorescence spectra of harmol and harmalol in the solid phase at 77 K. Three molecular species, namely, the cation, the neutral molecule and the molecular anion are characterized for harmol in both the fluorescence and phosphorescence spectra. We have also identified three molecular species, namely, the cation, the zwitterion and the molecular anion in the fluorescence spectra of harmalol but only the cation and the molecular anion in the phosphorescence spectra.</p><p>The excited state p<em>K</em>_a values in the first excited triplet state T₁ have been estimated from the Förster equation. It is found that in the first excited triplet state the ring nitrogen atom is more basic and the hydroxy group is more acidic than in the ground state.</p></div>","PeriodicalId":16771,"journal":{"name":"Journal of Photochemistry","volume":"39 2","pages":"Pages 273-283"},"PeriodicalIF":0.0,"publicationDate":"1987-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0047-2670(87)80038-2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86483321","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Photoresponsive peptide and polypeptide systems IV: Light-induced conformational changes in ϵ-poly(l-lysine) wit photochromic side chains","authors":"Hiroyuki Yamamoto,&nbsp;Yasuko Miyagi,&nbsp;Ayako Nishida,&nbsp;Toru Takagishi,&nbsp;Shoji Shima","doi":"10.1016/0047-2670(87)80043-6","DOIUrl":"10.1016/0047-2670(87)80043-6","url":null,"abstract":"<div><p>ϵ(Poly(<span>l</span>-lysine) containing a high mole percentage of azo aromatic side chains was synthesized by the active ester method. The photochemical properties of the azo polypeptide, ϵ-poly(<em>N</em>^α-phenylazobenzoyl-<span>l</span>-lysine) (ϵ-PPABLL), were investigated by absorption and circular dichroism (CD) spectroscopy in hexafluoro-2-propanol (HFIP). The photochromism of the absorption band in the near UV and visible wavelength region was found to be mostly reversible as a function of irradiation time at different wavelengths (360 nm and 460 nm) owing to the trans—cis photoisomerization of the azo aromatic moieties. The CD spectrum exhibited multistage photochromism on irradiation by light. The whole CD spectrum, especially at the dichroic bands at 300 nm (positive), 340 nm (negative) and 365 nm (trans, positive), showed a peculiar reversible photochromism on irradiation by 360 nm and 460 nm light, except the first irradiation time course. The position and magnitude of the negative dichroic band at 225 nm suggested that the backbone conformational change of ϵ-PPABLL was a light-induced partial reversible transition from a β-form-rich structure to a random-coil-rich structure.</p></div>","PeriodicalId":16771,"journal":{"name":"Journal of Photochemistry","volume":"39 2","pages":"Pages 343-350"},"PeriodicalIF":0.0,"publicationDate":"1987-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0047-2670(87)80043-6","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79293188","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Methylene-blue-sensitized photochemical hydroxylation of 2-hydroxybenzoic acid by hydrogen peroxide: photocatalytic effect of ferric chloride","authors":"Stanislav Luňák,&nbsp;Petr Sedlák,&nbsp;Pavel Lederer","doi":"10.1016/0047-2670(87)80035-7","DOIUrl":"10.1016/0047-2670(87)80035-7","url":null,"abstract":"<div><p>The methylene-blue-sensitized hydroxylation of 2-hydroxybenzoic acid by hydrogen peroxide initiated by visible radiation and catalysed by ferric chloride has been investigated. The major reaction product is 2,3-dihydroxy-benzoic acid. In the absence of iron(III), the reaction occurs extremely slowly. Iron(III) is observed to have an appreciable catalytic effect on the photosensitized reaction at concentrations as low as 10⁻⁸ M. The first step of the reaction is the photochemical reduction of iron(III) to iron(II), <em>i.e.</em> the generation of Fenton's reagent.</p></div>","PeriodicalId":16771,"journal":{"name":"Journal of Photochemistry","volume":"39 2","pages":"Pages 239-250"},"PeriodicalIF":0.0,"publicationDate":"1987-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0047-2670(87)80035-7","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75370971","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Phosphorescence emission and polarization of harmane","authors":"A. Olba,&nbsp;F. Tomás,&nbsp;I. Zabala,&nbsp;P. Medina","doi":"10.1016/0047-2670(87)80037-0","DOIUrl":"10.1016/0047-2670(87)80037-0","url":null,"abstract":"<div><p>Phosphorescence and excitation spectra, phosphorescence and excitation polarization spectra and phosphorescence lifetimes were measured in methylcyclohexane (MC) and EPA glasses at 77 K for harmane (1-methyl-9<em>H</em>-pyrido[3,4-<em>b</em>]indole).</p><p>It has been found that the 0—0 band of the phosphorescence emission is polarized out of plane, using the excitations corresponding to absorptions into the first and second excited ππ^* singlet states. This fact and the order of the lifetimes measured indicate an emitting triplet that is ³(ππ^*) in both solvents. The origin of this polarization is very likely ¹(nπ^*) → ³(ππ^*) mixing as a result of spin–orbit coupling. However, the vibrational structure and changing polarization outside the OO band indicate that second-order effects involving spin—orbit coupling and vibronic interactions are important and the mixing scheme appears to be <figure><img></figure></p><p>The “proximity effect” can qualitatively explain the low intensity of phosphorescence and the stronger vibronic interaction between the nπ^* and ππ^* states of harmane in a hydrocarbon solvent (MC).</p></div>","PeriodicalId":16771,"journal":{"name":"Journal of Photochemistry","volume":"39 2","pages":"Pages 263-272"},"PeriodicalIF":0.0,"publicationDate":"1987-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0047-2670(87)80037-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73133711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}