Search results for "absorptio"
showing 10 items of 2815 documents
Red- and Blue-Shifts in Oligo(1,4-phenyleneethynylene)s Having Terminal Donor−Acceptor Substitutions
2004
Four series of oligo(1,4-phenyleneethynylene)s (OPEs), 1−4 (a−d), each having a terminal dialkylamino group as their electron donor, were prepared by applying Sonogashira−Hagihara reactions and a protecting group strategy. To study the influence that the push−pull effect has on the long-wavelength absorption, three of the four series of OPEs contain terminal acceptor groups (CN, CHO, NO2). Extending the conjugation (increasing the number of repeat units, n) lowers the energy E(n) of the electron transition in the purely donor-substituted series 1a−4a (bathochromic shift). This effect is superimposed in the push−pull series 1−4 (b−d) by the effect of the intramolecular charge transfer (ICT),…
Cation-induced self-assembly of an amphiphilic perylene diimide derivative in solution and Langmuir–Blodgett films
2015
Abstract A novel amphiphilic perylenetetracarboxylic diimide (PDI) derivative, N-(4′-benzo-15-crown-5-ether)-N-hexyl-1,7-di(4-tert-butyl-phenoxy)perylen-3,4,9,10-tetracarboxylic diimide (15C5PDI), has been synthesized and characterized. Dimerization of 15C5PDI is induced in CHCl 3 solution with the present of K + , resulting in the formation of the slipped co-facial J -aggregates, as revealed by absorption and fluorescence spectroscopies. Analysis of the surface pressure–area ( π – A ) isotherms and spectral change for the monolayer formed at the air/water interface, disclosed that 15C5PDI molecules adopted the H -type aggregation mode with a face-to-face configuration and edge-on orientati…
Konvergenz von Absorption und Fluoreszenz bei gekreuzt konjugierten Oligomeren aus Chalkon-Bausteinen
1999
The absorption and fluorescence spectra of two series of chalcone oligomers (1a–d) and (2a–d) are reported. Due to small or vanishing orbital coefficients (HMO calculation) within the cross-conjugated systems, the bathochromic shifts caused by the extension of the chains are modest. The effective conjugation lengths amount to 6 and 14 chalcone building blocks in the absorptions of the series 1 and 2. The convergence of the fluorescence bands is already reached in 1d and 2d with 4 and 8 enone units, respectively. Besides the uniform or alternate arrangement of the chalcone building blocks, the positions of the propoxy substituents show a considerable influence on the electronic transitions p…
Dielektrische Relaxation und aromatischer Bindungszustand der Amino- und Hydroxylgruppe
1965
Bei funf Wellenlangen im Bereich von 60 cm bis 7 mm wurde in benzolischer Losung bei 20 °C die dielecktrische Absorption von Benzolderivaten gemessen, die Amino- oder Hydroxylgruppen enthalten. Danach erfolgt die elektrische Dipolorientierung bei N, N'-Dimethylanilin, Diphenylamin und ver wandten Molekulen in der Art, das die drei Bindungen des Stickstoffs uber die ebene Anordnung hinweg umklappen. Ebenso kann auch das Relaxationsverhalten von Anilin beschrieben werden. Voraussetzung fur diese Inversion ist die mesomere Wechselwirkung zwischen dem Stickstoff und einem aromatischen ϕ-Elektronen-system. Dagegen ergeben die Meswerte keinen Hinweis darauf, das bei der Hydroxylgruppe auch eine s…
A new interpretation for the structure of the VN bands of ethylene
1971
Abstract Potential surfaces for CC stretch and CH2 twisting of ethylene obtained by the combined SCF CI method lead to the prediction that non-vertical transitions are responsible for the absorption maximum in the VN bands and that the broad diffuse nature of the spectrum in this region could well be caused by the proximity of two states of the same symmetry of the twisted molecule.
Stability in physiological saline of intravenous busulfan in a polyolefin pack
2008
Abstract Introduction Although it has been used orally, the variability in its absorption and the risk of causing vomiting has lead to a push towards the intravenous use of busulfan. This study looks at the stability of 60 mg of busulfan, in fixed volumes of 250 mL (0.24 mg/mL) and 500 mL (0.12 mg/mL) of physiological saline and different conservation conditions, in a new plastic pack made from polyolefin/polyamide laminates. Material and methods High-performance liquid chromatography with ultraviolet detection was used to determine the concentration of busulfan derivate with sodium diethyldithiocarbamate trihydrate. Stability was assessed for both concentrations; refrigerated and at room t…
Specific dye adsorption at oriented monolayers
2007
We studied the adsorption of water soluble cyanine dyes (pseudoiso-cyanine and “stains-all”) to monomolecular layers of arachidic acid at the water-air interface in a Langmuir trough. Fluorescence microscopy was employed to on-line monitor the formation of J-aggregates upon adsorption. Large two-dimensional monodomain single crystals could be grown by this self-assembly process with optical properties reminiscent of those found and extensively studied for amphiphilic derivatives of the same chromophors [12]. In addition to the necessary Coulombic interaction between subphasedye and target monolayer, we found that details of the crystal morphology also crucially depend on substrate parameter…
Effect of Mn Doping on the Optical Properties of Chalcogenide Compounds ZnS and ZnTe
2020
In this paper, the influence of the addition of Mn on the optical properties of the binary compounds ZnS and ZnTe deposited by a close-spaced vacuum sublimation method onto nonoriented glass at different substrate temperatures was considered. The spectral dependences of the transmittance T (λ), reflectance R (λ) and the absorption α (λ), as well as the bandgap for each material (Eg) were measured and calculated.
Optical properties of lithium niobate single crystals
2005
Studies of thermal and γ-irradiation effects on the optical properties in congruous lithium niobate single crystals containing Y, Mg, Gd, B, and Zn dopants including samples with double dopants Y, Mg and Gd, Mg are reported. Formation of defects at irradiation and thermal treatment of the samples is explored by electron absorption spectra. Considerable increase of absorption with the dose of γ-radiation is observed at 500 nm. The changes of absorption examined under different conditions are explained by creation and destruction of Nb 4 + defects.
On the Occurrence of Flavonoids in the acrocarpous Mosses
1978
Summary By means of paper chromatography two flavonoids were isolated from the methanolic extract of the moss Mnium undulatum. One substance was identified by chromatographic data, absorption spectra and acid hydrolysis as isovitexin-7-0-glucoside (saponarin). The second substance resists acid hydrolysis and is by chromatography and absorption spectrum identical with apigenin-6,8-di-C-glycoside (viccnin).