Maximum absorption wavelength

A third topic will be the molecular weight dependance of the UV absorption maxima wavelengths. 

Therefore, the concentration of each pigment can be estimated from the absorption coefficients at the absorption maximum wavelength of the first pigment, corrected by the absorption contribution of the second pigment by creating equations that solve for two unknown pigments. 

When parameters of the Pariser-Parr-Pople configuration interaction molecular orbital (PPP-CI MO) method were modified so as to reproduce the Aol)s values for l,3-di(5-aryl-l,3,4-oxadiazol-2-yl)benzenes 16 and 17, the calculated HOMO and LUMO energy levels corresponded with the experimental ionization potential and electron affinity values. The relationships between the electrical properties and molecular structures for the dyes were investigated. The absorption maximum wavelengths for amorphous films were found to be nearly equal to those for solution samples <1997PCA2350>. 

Absorption maximum wavelengths, correlation equations for, 20 508t Absorption, metabolism, distribution, and excretion (ADME), predicting using diversity analysis, 6 18 Absorption properties, of sutures,... 

The useful spectral range is usually found between 700 and 200 nm. (The region below 200 nm is the vacuum ultraviolet, which requires special instrumentation and, for this reason, is less important.) The spectrum is the result of measuring the absorption of light versus wavelength. The position of the absorption maximum (wavelength = peak position), is important, as is related to the amount of radiation absorbed (molar absorptivity, e). 

Scheme 5). On the other hand, when the substituent R is of a suitable size, an intramolecular ion pair such as structure 38 will be formed and stabilized by interionic hydrogen bond N+ —H—O- in addition to hydrogen bond N+—H—O and ion-dipole interaction N +—O. At the same time, the solution will be turned to violet because of short interionic distance between N + and O, which is strongly affected on the electronic state of the dinitrophenylazophenol chromophore. Accordingly, the absorption maximum wavelengths of the amine complexes in visible spectra will possibly be indicative of the type of complex, i.e. salt complex (abbreviated as saltex) 38 or simple salt 39. 

In a polar polymer, i.e., cellulose acetate (CA) or nitrocellulose (NC) 35E, 35Z, and 36 had a relatively longer absorption maximum wavelength than in less polar matrices. In NC the of 36 shifts to 528 nm, which is also longer than in organic solvents. The role of polymer films in the quantum yields of photoreactions is not clear. In a comparison of the photochemical properties of 35 in polymer films and in solvents, it was found that the E c in polymer matrices was substantially smaller than that in the corresponding solvent with similar polarity. However, the decoloration quantum yield Oc e in a polymer film was larger than that in solvents. In conclusion, the polymer matrix properties, such as polarity, viscosity, and glass transition temperature (Tg) are quite important for photochromic reactions and applications. The coloration, E — Z and Z —> E isomerizations were suppressed in polymer matrices. 

The difference in the absorption maximum wavelengths between the E form and Z form was not large. The deviation was only about 10 nm when R3 was an ethyl group. The Zmax of the colored form was 616 nm, which was a 32-nm bathochromic shift compared with the methyl group-substituted fulgide, suggesting that the steric hindrance effect of R3 on the planar molecular structure of the colored form must be considered. 

Table 4.18. Solvent Effect on the Absorption Maximum Wavelength (Xmax) of Fulgide 62...

Absorption maximum Wavelength at which greatest absorption occurs... 

As an intern in a food industry laboratory you are about to prepare a 500.0 L solution of FD C Yellow 6 ("Sunset Yellow") for a batch of Jell-o . Afterward, you will check its concentration by measuring absorbance at 481 nm, the absorption maximum wavelength for this dye. The lab procedure says you should weigh and dissolve 0.6113 g of the dye and dissolve it in a 500.0 L vat of water. The molecular mass of sunset yellow, or disodium 6-hydroxy-5-[(4-sulfophenyl)azo]-2-naphthalenesulfonate, is 452.37 g mol and its absorption coefficient at 481 nm, 6481, b 5.55x10 L mol cm T V /hat absorbance, A481, do you expect of this solution ... 

Zhao, H., Lu, W. C., Liu, L. and Song, H. F. (2004). Support vector machine applied to prediction of absorption maximum wavelength of azo dyestuff, Acta chemica sinica, pp. 649-656. 

Fig. 5 Photoluminescence spectra of polymer 13 and compound 19 in CHQ3 (1.0 X10" M) excited at each absorption maximum wavelength...

The shape of the broad absorption curve in Figure 9.17 is typical of that of any dye suitable for a laser. It shows an absorption maximum to low wavelength of the Og band position, which is close to the absorption-fluorescence crossing point. The shape of the absorption curve results from a change of shape of the molecule, from Sq to 5i, in the... 

Resonance Raman Spectroscopy. If the excitation wavelength is chosen to correspond to an absorption maximum of the species being studied, a 10 —10 enhancement of the Raman scatter of the chromophore is observed. This effect is called resonance enhancement or resonance Raman (RR) spectroscopy. There are several mechanisms to explain this phenomenon, the most common of which is Franck-Condon enhancement. In this case, a band intensity is enhanced if some component of the vibrational motion is along one of the directions in which the molecule expands in the electronic excited state. The intensity is roughly proportional to the distortion of the molecule along this axis. RR spectroscopy has been an important biochemical tool, and it may have industrial uses in some areas of pigment chemistry. Two biological appHcations include the deterrnination of helix transitions of deoxyribonucleic acid (DNA) (18), and the elucidation of several peptide stmctures (19). A review of topics in this area has been pubHshed (20). 

There are two main kinds of dye aggregates, characterized by their typical spectral properties J-aggregates and H-aggregates. The absorption band maximum (f-band) of the J-aggregates is shifted bathochromicaHy with respect to that of an isolated molecule (M-band) the absorption maximum of the H-aggregates is shifted hypsochromicaHy (H-band). The dyes can also form dimers with a shorter absorption wavelength (D-band). 

A quantitative expression of these observations is shown in equation 1, where is the observed absorption maximum for the unsymmetrical carbocyanine and Xj is the arithmetic mean (isoenergetic wavelength) for the absorption maxima of the related symmetrical dyes. 

Isothiazole has an absorption maximum in ethanol solution at 244 nm, with a molar absorptivity of 5200. This absorption occurs at a longer wavelength than with pyrazole or isoxazole, the displacement being due to the presence of the sulfur atom. A series of approximate additive wavelength shifts has been drawn up in Table 11 and this should enable prediction of UV maxima of isothiazoles with reasonable accuracy, even for multiply substituted compounds. The longest wavelength band results from a electronic... 

Absorption spectra of standard solutions of Cyt c was obtained at different concentration. Maximum of absolution was observed at wavelength 410 nm. It is known haemoglobin and other haems have absolution maximum at the same wavelength. For elaboration of selective method of Cyt c determination in semm of mice its reaction with phtalocyanine of copper was investigated. Absorption maximum of Cyt c with Cu phtalocyanine in H SO was observed at wavelength 710 nm. Dependence on optical density at 710 nm against concentration of Cyt c have linear character in range 0.162-10-"-6.49-10 mol/L. 

---