scholarly journals The Very Weak Visible Absorption Band ofp-Benzoquinone

1962 ◽  
Vol 35 (2) ◽  
pp. 295-298 ◽  
Author(s):  
Akira Kuboyama
Keyword(s):  
Absorption Band ◽  
Visible Absorption

Octahedral–tetrahedral equilibria in aqueous cobalt(II) solutions at high temperatures

1980 ◽  
Vol 58 (14) ◽  
pp. 1418-1426 ◽  
Author(s):  
Thomas Wilson Swaddle ◽  
Leonard Fabes
Keyword(s):  
Sulfuric Acid ◽  
High Temperature ◽  
Absorption Band ◽  
High Temperatures ◽  
Intensity Ratio ◽  
Hydrogen Sulfate ◽  
Sulfate Ion ◽  
Acidic Media ◽  
Visible Absorption ◽  
Upper Limits

Evidence is presented to indicate that aqueous Co2+ exists as the hexaaquo-ion in equilibrium with minor amounts (upper limits 0.08% at 298 K, 7% at 625 K, at 16–25 MPa) of tetraaquocobalt(II), with ΔH ~ +17 kJ mol−1. The single visible absorption band of the supposed Co(H2O)42+ has maxima at 552 nm and 486 nm in the intensity ratio 2:1. Hydrogen sulfate ion (up to 0.5 M at least) does not complex Co2+(aq) detectably in acidic media, 290–625 K, and sulfuric acid therefore holds promise as a non-complexing strong monobasic acid for high-temperature aqueous studies. In water containing 2.0 M or more Cl−, the tetrahedral form of cobalt(II) is CoCl42−, ΔH for the octahedral → tetrahedral equilibrium being +62 kJ mol−1; forCoBr42−, the corresponding ΔH is +70 kJ mol−1, the greater endothermicity accounting entirely for the lower stability relative to CoCl42−.

Synthesis and Properties of 1-[2-trifluoromethylpheny-2-[2-methyl-5-(3,5-difluorophenyl)-3-thienyl] perfluorocyclopentene

2013 ◽  
Vol 468 ◽  
pp. 75-78
Author(s):  
Guang Ming Liao ◽  
Shou Zhi Pu ◽  
Zhi Yuan Sun
Keyword(s):  
Absorption Band ◽  
Fluorescence Intensity ◽  
Emission Intensity ◽  
Uv Light ◽  
Fluorescent Properties ◽  
Visible Absorption ◽  
Photostationary State ◽  
Closed Ring ◽  
Open Ring

An asymmetrical photochromic diarylethene 1-[2-trifluoromethylpheny-2-[2-methyl-5-(3,5-difluorophenyl)-3-thienyperfluorocyclopentene (1o) was synthesized and its phtochromic, fluorescent properties in both solution and PMMA films were investigated in detail. This compound exhibited remarkable photochromism, upon irradiation with 297 nm UV light, the colorless solution of 1o turned to plum with a new visible absorption band centered at 544 nm (ε =3.75 × 103 L mol-1 cm-1) attributable to the closed-ring isomer 1c.The fluorescence intensity of diarylethene decreased dramatically along with the photochromism from open-ring isomer to closed-ring isomer in PMMA films and in hexane. The emission intensity of diarylethene 1o in a photostationary state was quenched to ca. 64% in hexane and 27% in PMMA films.

scholarly journals Metaretinochrome in membranes as an effective donor of 11-cis retinal for the synthesis of squid rhodopsin.

1984 ◽  
Vol 84 (1) ◽  
pp. 49-62 ◽  
Author(s):  
T Seki
Keyword(s):  
Absorption Band ◽  
Schiff Bases ◽  
Sodium Dodecyl ◽  
Electrophoretic Pattern ◽  
Difference Spectrum ◽  
Main Peak ◽  
Visible Absorption ◽  
The Difference ◽  
Protein Moiety

Aporetinochrome, which is a protein moiety of retinochrome without chromophore retinal, is found in the membrane containing retinochrome. All of the prosthetic retinal of retinochrome in membranes, which is all-trans retinal, is bound to the chromophoric site on the protein moiety, with protonated Schiff bases showing an absorption band with the maximum at 495 nm. On exposure to light, retinochrome is converted to metaretinochrome at room temperature. The prosthetic retinals of metaretinochrome in membranes, which are 11-cis retinals, are in two states: retinals bound to the chromophoric site with protonated Schiff bases, and the free retinals, which are separated from the protein moiety. These states are suggested from the following observations. (a) The ratio of the absorbance at 470 nm of metaretinochrome to that at 495 nm of the parental retinochrome differs because of differences in samples and is higher in the purer preparations. (b) The difference spectrum of absorption of metaretinochrome caused by alkalinization shows two minimum peaks at approximately 420 and 470 nm. (c) The rate of bleaching of metaretinochrome in membranes with dilute NH2OH is much faster than that of retinochrome, and the absorption band in the near-UV region is more susceptible to NH2OH than the visible absorption band. The state of the prosthetic retinals in metaretinochrome was confirmed directly by the reaction of metaretinochrome in membranes with NaBH4. After treatment with NaBH4, the sodium dodecyl sulfate-polyacrylamide gel electrophoretic pattern shows two fluorescent bands: one at the position that corresponds to the retinochrome protein (mol wt 27,000 +/- 2,000), and another at the front of migration, where no band of protein is observed. Retinoids extracted from the NaBH4-treated metaretinochrome in membranes and analyzed with high-pressure liquid chromatography show a main peak of 11-cis retinol. The results of this and earlier (Seki et al., 1982) papers are summarized, and it is strongly suggested that metaretinochrome in the squid retina may play the role of 11-cis retinal donor for opsin and contribute to the synthesis of the squid rhodopsin.

Synthesis and Properties of 1-(2-Methyl-3-benzothiophene)-2-[2-methyl-5-(3-fluoro-4-chloro)phenyl-3-thienyl]perfluorocyclopentene

2014 ◽  
Vol 1078 ◽  
pp. 98-101
Author(s):  
Guan Ming Liao ◽  
Chun Hong Zheng ◽  
Shou Zhi Pu
Keyword(s):  
Absorption Band ◽  
Emission Intensity ◽  
Uv Light ◽  
Order Reaction ◽  
First Order Reaction ◽  
Fluorescent Properties ◽  
Visible Absorption ◽  
First Order ◽  
Photostationary State ◽  
Closed Ring

An asymmetrical photochromic diarylethene1-(2-Methyl-3-benzothiophene)-2-[2-methyl-5-(3-fluoro-4-chloro) phenyl-3-thienyl] perfluorocyclopentene (1o) was synthesized and its phtochromic, fluorescent properties were investigated in detail. This compound exhibited remarkable photochromism, upon irradiation with 297 nm UV light, the colorless solution of 1o turned to violetred with a new visible absorption band centered at 538 nm (ε = 1.17 × 104 L mol-1 cm-1) attributable to the closed-ring isomer 1c. The kinetic experiments showed that the cyclization and cycloreversion processes were zeroth and first order reaction, respectively. Moreover, diarylethene 1o also exhibited obviously fluorescence switches along with the photochromism.The emission intensity of diarylethene 1o in a photostationary state was quenched to ca. 27% in hexane.

Synthesis and Photochromism Studies of 1-(2-methyl-3-benzofuran)-2-[2-methyl-5-naphthyl-3-thienyl]perfluorocyclopentene

2014 ◽  
Vol 1078 ◽  
pp. 86-89
Author(s):  
Xiao Rong Dong ◽  
Hong Yan Xu ◽  
Shou Zhi Pu
Keyword(s):  
Absorption Band ◽  
Uv Light ◽  
Amorphous Film ◽  
Order Reaction ◽  
Pmma Film ◽  
Zeroth Order ◽  
Fluorescent Properties ◽  
Visible Absorption ◽  
First Order ◽  
Photochromic Reaction

A novel photochromic diarylethene was synthesized and its photochromic and fluorescent properties were investigated. The results showed that this compound exhibited reversible photochromism, changing from colorless to amaranth after irradiation with UV light both in solution and PMMA amorphous film. In hexane, compound 1a exhibited an absorption peak at 266 nm, upon irradiation with 297 nm light, a new visible absorption band centered at 530 nm emerged while the original peak at 266 nm decreased. In PMMA amorphous film, diarylethene 1a also showed good photochromism as similar to that in solution. The photochromic reaction kinetics indicated that the cyclization processes of 1a belong to the zeroth order reaction and the cycloreversion process belong to the first order reaction. Diarylethene 1a also exhibited good fluorescent switching both in solution and in PMMA film upon alternating irradiation with UV and visible light.

Effects of Substrate Temperature and External Poling Field on Molecular Orientation and Aggregation in Vacuum Deposited Photo Responsive DR1 Films

2003 ◽  
Vol 12 (02) ◽  
pp. 213-219
Author(s):  
H. Taunaumang ◽  
R. Hidayat ◽  
M. O. Tjia
Keyword(s):  
Absorption Band ◽  
Electric Field ◽  
Substrate Temperature ◽  
Molecular Orientation ◽  
Blue Shift ◽  
Poling Field ◽  
Visible Absorption ◽  
Oriented Molecules ◽  
Disperse Red 1 ◽  
Substrate Temperatures

A series of absorption spectroscopy measurements have been conducted on photo responsive Disperse Red 1 (DR1) films vacuum deposited at different substrate temperatures, with and without the presence of external poling field. Compared with the spectrum in solution, the spectra of DR1 films are generally featured by a pronounced depression of the visible absorption band and the appearance of a new peak at considerably shorter wavelength. A further depression of the absorption band and enhancement of the new peak are observed in the films deposited at higher substrate temperatures or in the presence of poling electric field, without showing, however, visible increase of the corresponding blue shift. These changes are attributed to increased portion of the vertically oriented DR1 molecules without resulting in higher packing of the oriented molecules.

Two types of localized excess electrons in crystalline D2O ice

1977 ◽  
Vol 55 (12) ◽  
pp. 2385-2395 ◽  
Author(s):  
George V. Buxton ◽  
Hugh A. Gillis ◽  
Norman V. Klassen
Keyword(s):  
Absorption Band ◽  
Infrared Absorption ◽  
Low Temperatures ◽  
Total Yield ◽  
Equilibrium Concentration ◽  
Electron Trap ◽  
Decay Kinetics ◽  
Infrared Band ◽  
Visible Absorption ◽  
Perfect Lattice

In a pulse radiolysis study of crystalline D2O ice, an intense infrared absorption band with λmax > 2350 nm has been found at low temperatures, in addition to the well-known visible absorption band of the trapped electron. The infrared band is also attributed to trapped electrons, partly because of its similarity to the electron absorption band found recently in some D2O glasses at low temperatures. The effects of temperature, dose per pulse, accumulated dose, and added NH4F, HF, and ND3 on the yields and decay kinetics of both bands have been investigated. It is concluded that the electron trap giving rise to the visible band is a vacancy which at low temperatures is radiation-produced by a two-step spur process. At temperatures close to the melting point the vacancy-trap probably exists before the radiation pulse at equilibrium concentration. The electron trap which gives rise to the infrared band is thought to be a cavity that occurs naturally in the perfect lattice. For previously unirradiated samples the infrared band decays by a second order process which is remarkably fast [Formula: see text] The decay reaction is probably neutralization by D2O+. Doping with NH4F increases the yield of the infrared absorption and greatly decreases its decay rate. The total yield of localized electrons in irradiated crystalline D2O is higher than has been generally recognized.

Research on Photochromic Materials with Synthesis and Properties of 1-(2-Methyl-3-Benzothiophene)-2-[2-Methyl-5-(3-Cyanophenyl)-3-Thienyl]Perfluorocyclopentene

2014 ◽  
Vol 662 ◽  
pp. 95-98
Author(s):  
Guang Ming Liao ◽  
Chun Hong Zheng ◽  
Shou Zhi Pu
Keyword(s):  
Absorption Band ◽  
Emission Intensity ◽  
Uv Light ◽  
Pmma Film ◽  
Fluorescent Properties ◽  
Visible Absorption ◽  
Photostationary State ◽  
Closed Ring ◽  
Photochromic Materials

An asymmetrical photochromic diarylethene1-(2-Methyl-3-benzothiophene)-2-[2-methyl-5-(3-cyanophenyl)-3-thienyl] perfluorocyclopentene (1o) was synthesized and its phtochromic, fluorescent properties in both solution and PMMA films were investigated in detail. This compound exhibited remarkable photochromism, upon irradiation with 297 nm UV light, the colorless solution of 1o turned to violet with a new visible absorption band centered at 535 nm (ε = 1.08 × 104 L mol-1 cm-1) attributable to the closed-ring isomer 1c. The emission intensity of diarylethene 1o in a photostationary state was quenched to ca. 32% in hexane and 43% in PMMA film.

Coordination complexes of amino acids: Preparation and properties of some Amino-acidatobis(acetylacetonato)cobalt(III) and Bis(amino-acidato)(acetylacetonato)cobalt(III) complexes

1968 ◽  
Vol 21 (3) ◽  
pp. 679 ◽  
Author(s):  
SH Laurie
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Absorption Band ◽  
Absorption Spectra ◽  
Coordination Complexes ◽  
Optically Active ◽  
Ultraviolet Absorption ◽  
Visible Absorption ◽  
Molecular Weights ◽  
Cotton Effects

Complexes of the type [Co(acac)2(aa)] have been synthesized, in which the amino acid is DL- and L-phenylalanine, L-valine, L-leucine, L-proline, DL-, L-,and D-alanine, and glycine. The complexes were characterized by means of analyses, molecular weights, and their infrared, visible, and ultraviolet absorption spectra. During the syntheses several of the bis(amino-acidato) complexes, [Co(acac)(aa)2], were also formed; the L-phenylalanine and glycine complexes were isolated and characterized. The complexes prepared from the optically active amino acids exhibited Cotton effects in the region of the visible absorption band (lA1g, + 1T1g). These effects have been attributed to induced asymmetry rather than stereoselectivity. Amino acids of the same configuration gave rise to Cotton effects of the same sign, ie. (-)590-[Co(acac)2(L-aa)], (-)6590-[Co(acac)(L-aa)2], and (+)590-[Co(acac),(D-aa)].

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