Hexa-peri-benzocoronene, a candidate for the origin of the diffuse interstellar visible absorption bands ?

Tetrahedron ◽  
1986 ◽  
Vol 42 (4) ◽  
pp. 1127-1134 ◽  
Author(s):  
W. Hendel ◽  
Z.H. Khan ◽  
W. Schmidt
Keyword(s):  
Absorption Bands ◽  
Visible Absorption

Meso-aryl-ß-pyrrolic positions interactions in meso-tetraarylporphyrins: Flat arylporphyrins and building blocks for oligoporphyrins

2004 ◽  
Vol 08 (02) ◽  
pp. 111-119 ◽  
Author(s):  
Henry J. Callot ◽  
Romain Ruppert ◽  
Christophe Jeandon ◽  
Sébastien Richeter
Keyword(s):  
Building Blocks ◽  
Absorption Bands ◽  
Visible Absorption ◽  
Aryl Ring ◽  
Porphyrin Macrocycle ◽  
Uv Visible

Aryl groups bound to the meso positions of porphyrins often react with neighboring groups, in particular ß-acyl groups to give highly diversified monomeric and dimeric new functionalized porphyrins. The products, whose meso-aryl ring approaches coplanarity with the porphyrin macrocycle, show large shifts of UV-visible absorption bands and various potentialities for building external chelating moieties and assembling oligoporphyrins.

Initial Reaction Intermediates in the Oxidation of Ascorbic Acid by Nitrous Acid

1981 ◽  
Vol 44 (1) ◽  
pp. 28-32 ◽  
Author(s):  
JAY B. FOX ◽  
ROSEMARY N. FIDDLER ◽  
AARON E. WASSERMAN
Keyword(s):  
Nitric Oxide ◽  
Ascorbic Acid ◽  
Nitrous Acid ◽  
Organic Radicals ◽  
Initial Reaction ◽  
Reaction Intermediates ◽  
Absorption Bands ◽  
Visible Absorption ◽  
Decomposition Products

Nitrite and ascorbate react to form nitric oxide at pH 5.5. In the initial stages of the reaction, seven intermediates can be identified spectrally and chromatographically; these include two colorless nitroso derivatives which contain 30–60% of the initial nitrite, two nitroso reductant derivatives absorbing at 345 and 412 nm, diketogulonic acid and two further decomposition products. None of the intermediates was paramagnetic; except for diketogulonic acid, all decomposed rapidly during or after isolation. Based on the order of appearance of the ultraviolet and visible absorption bands in the reaction mixtures, the observed characteristics of the intermediates, and the lack of organic radicals, a sequence is proposed for the initial steps in the oxidation of ascorbic acid by nitrous acid.

A spectroscopic study of the solvent dependent processes of the anils of benzaldehyde and salicylaldehyde

1982 ◽  
Vol 60 (13) ◽  
pp. 1727-1737 ◽  
Author(s):  
Jerry W. Lewis ◽  
Camille Sandorfy
Keyword(s):  
Hydrogen Bond ◽  
Ground State ◽  
Spectral Characteristics ◽  
Infrared And Raman Spectra ◽  
Absorption Data ◽  
Absorption Bands ◽  
Visible Absorption ◽  
Raman Spectral ◽  
Dependent Processes ◽  
Electronic Ground

The ultraviolet–visible, infrared, and Raman spectral characteristics of some anils of benzaldehyde and salicylaldehyde in several solvents have been investigated. The ultraviolet–visible absorption data indicate that in solvents with a proton donating ability less than or equal to trifluoroethanol a single equilibrium exists in solutions of N-(2-hydroxybenzylidene)aniline, whereas in solvents with a proton donating ability equal to or greater than hexafluoroisopropanol more than one equilibrium occurs. The infrared spectra of this compound dissolved in trifluoroethanol do not show new absorption bands in the 1700–1500 cm−1 region; however, new absorption bands in this region do appear when hexafluoroisopropanol is employed as solvent. From these data it is inferred that the first equilibrium involves the breaking of the chelate hydrogen bond and the second equilibrium involves actual protonation of N-(2-hydroxybenzylidene)aniline in the electronic ground state. A comparison of the infrared and Raman spectra of the title compounds is also made and alternate assignments for several observed bands in the 1700–1500 cm−1 region are proposed.

Spectroelectrochemical Study of some μ3-Oxo-μ-acetato Trinuclear Rhodium(III) and Iridium(III) Complexes

1995 ◽  
Vol 50 (4) ◽  
pp. 551-557 ◽  
Author(s):  
Kenta Takahashi ◽  
Keisuke Umakoshi ◽  
Akihiro Kikuchi ◽  
Yoichi Sasaki ◽  
Masato Tominaga ◽  
...  
Keyword(s):  
Absorption Spectrum ◽  
Electronic Absorption Spectrum ◽  
Absorption Spectra ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Visible Region ◽  
Absorption Bands ◽  
Visible Absorption ◽  
The One ◽  
Species Being

New trinuclear rhodium(III) complexes, [Rh3(μ3-O)(μ-CH3COO)6(L)3]+ (L = imidazole (Him), 1-methylimidazole (Meim), and 4-methylpyridine (Mepy)) have been prepared. The Him, Meim, and Mepy complexes show reversible one-electron oxidation waves at E1/2 = +1.12, +1.12, and +1.28 V vs Ag/AgCl, respectively, in acetonitrile. Electronic absorption spectra of the one electron oxidized species of these complexes and [Rh3(μ3-O)(μ-CH3COO)6(py)3]+ (py = pyridine) (E1/2 = +1.32 V ) were obtained by spectroelectrochemical techniques. While the Rh3(III,III,III) states show no strong visible absorption, the Rh3(III,III,IV ) species give a band at ca. 700 nm (ε = 3390-5540 mol dm-3 cm-1). [Ir3(μ3-O)(μ-CH3COO)6(py)3]+ with no strong absorption in the visible region, shows two reversible one-electron oxidation waves at +0.68 and +1.86 V in acetonitrile. The electronic absorption spectrum of the one-electron oxidized species (Ir3(III,III,IV )) also shows some absorption bands (688 nm (ε, 5119), 1093 (2325) and 1400 (ca. 1800)). It is suggested that the oxidation removes an electron from the fully occupied anti-bonding orbital based on metal-dπ-μ3-O-pπ interactions, the absorption bands of the (III,III,IV ) species being assigned to transitions to the anti-bonding orbital.

scholarly journals Physiological performance by growth rate, pigment and protein content of the brown seaweed Sargassum filipendula (Ochrophyta: Fucales) induced by moderate UV radiation exposure in the laboratory

2020 ◽  
Vol 84 (1) ◽  
pp. 59
Author(s):  
Luz K. Polo ◽  
Fungyi Chow
Keyword(s):  
Growth Rate ◽  
Uv Radiation ◽  
Brown Seaweed ◽  
Physiological Parameters ◽  
Absorption Bands ◽  
Visible Absorption ◽  
Photosynthetic Organisms ◽  
Antioxidant Defence System ◽  
Sargassum Filipendula ◽  
Ecosystem Studies

UV radiation is a factor affecting the distribution and physiology of photosynthetic organisms in an aquatic ecosystem. Studies with macroalgae indicate diverse biological disturbances in response to UV radiation. This work aimed to study sensitivity of the brown macroalga Sargassum filipendula exposed to UV radiation: PAR (control), PAR+UVA+UVB(++) and PAR+UVA(++)+UVB. Changes in the physiological parameters growth rate, total soluble proteins, photosynthetic pigments and the UV-vis absorbing compounds were analysed after T0, T4, T7 and T10 (days) of UV exposure. Physiological parameters showed little variation between treatments and over time, suggesting that moderate UV radiation doses could regulate resistance responses to re-establish the cellular homoeostasis condition through activation of an antioxidant defence system, such as an overproduction of phenolic compounds. Responses recorded in S. filipendula would be related to acclimation mechanisms against acute UV radiation stress, triggering resistance responses to avoid serious damage to the metabolic machinery, activating control systems to maintain hormesis, and homoeostasis of deleterious actions of reactive species, similar to the phenomenon known as preparation for oxidative stress. Finally, UV-visible absorption spectra showed absorption bands evidencing the presence of mainly UV-absorbing compounds with photoprotective function, such as phlorotannins, flavonoids and carotenoids, which could provide adaptive advantages for organisms exposed to UV radiation.

scholarly journals A New Non-Centrosymmetricorganotin (IV) Hybrid Compound C5H14N2 [SnCl6] 2H2O: Crystal Structure And Optical Study Characterization

2021 ◽  
Author(s):  
Nejeh Hannachi ◽  
Thierry ROISNEL ◽  
Faouzi HLEL
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Optical Band Gap ◽  
X Ray Diffraction ◽  
Absorption Bands ◽  
Hybrid Compound ◽  
Visible Absorption ◽  
X Ray ◽  
Uv Visible ◽  
Absorption Measurements

Abstract A new non-centrosymmetricorganotin (IV) hybrid compoundC5H14N2 [SnCl6] 2H2O was determined by single crystal X-ray diffraction at 150(2) K. Its crystal structure was solved by single crystal X-ray diffraction reveling that compound crystallizes in the orthorhombic system with Pbca space group with the following lattice parameters: a = 12.1486 (15) Å, b= 15.4571 (17) Å, c = 16.7610 (18) Å with Z = 8. The bonding between inorganic and organic entities in the compounds is realized by hydrogen bonding O−H…O ,O−H…Cl , NH • • • Cl, N-H…Cl and O−H…Cl. Finally,UV-visible absorption measurements exhibit two absorption bands (226 nm and 262 nm).The optical band gap (Eg) is deduced to be 3.46 Ev.

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