Spectrum absorption visible

The preceding empirical measures have taken chemical reactions as model processes. Now we consider a different class of model process, namely, a transition from one energy level to another within a molecule. The various forms of spectroscopy allow us to observe these transitions thus, electronic transitions give rise to ultraviolet—visible absorption spectra and fluorescence spectra. Because of solute-solvent interactions, the electronic energy levels of a solute are influenced by the solvent in which it is dissolved therefore, the absorption and fluorescence spectra contain information about the solute-solvent interactions. A change in electronic absorption spectrum caused by a change in the solvent is called solvatochromism. 

FIGURE 21.9 Typical visible absorption spectra of cytochromes, (a) Cytochrome c, reduced spectrum (b) cytochrome c, oxidized spectrum (c) the difference spectrum (a) minus (b) (d) beef heart mitochondrial particles room temperature difference (reduced minus oxidized) spectrum (e) beef heart submitochondrial particles same as (d) but at 77 K. a- and /3- bauds are labeled, and in (d) and (e) the bauds for cytochromes a, h and c are indicated. 

A. Electronic (Ultraviolet and Visible) Absorption Spectra The electronic absorption spectra of heterocyclic molecules have their origins in the transitions of electrons between different molecular orbitals. In general, the more these orbitals are spread out in space, the closer together are their energy levels and the longer the wavelengths... 

Chase, A. M., and Brigham, E. H. (1951). The ultraviolet and visible absorption spectra of Cypridina luciferin solutions. J. Biol. Chem. 190 529-536. 

W.A. Schroeder et al, Ultraviolet and Visible Absorption Spectra in Ethyl Alcohol. 

The visible absorption maxima for a series of chlorinated dibenzo-p-dioxins in TFMS acid are tabulated in Table I. The visible absorption spectra of these compounds vary with the position and number of chlorine atoms. In general, a bathochromic shift was observed as more chlorine atoms were attached to the dibenzo-p-dioxin nucleus. 

A determination of dimethyl sulphoxide by Dizdar and Idjakovic" is based on the fact that it can cause changes in the visible absorption spectra of some metal compounds, especially transition metals, in aqueous solution. In these solutions water and sulphoxide evidently compete for places in the coordination sphere of the metal ions. The authors found the effect to be largest with ammonium ferric sulphate, (NH4)2S04 Fe2(S04)3T2H20, in dilute acid and related the observed increase in absorption at 410 nm with the concentration of dimethyl sulphoxide. Neither sulphide nor sulphone interfered. Toma and coworkers described a method, which may bear a relation to this group displacement in a sphere of coordination. They reacted sulphoxides (also cyanides and carbon monoxide) with excess sodium aquapentacyanoferrate" (the corresponding amminopentacyanoferrate complex was used) with which a 1 1 complex is formed. In the sulphoxide determination they then titrated spectrophotometrically with methylpyrazinium iodide, the cation of which reacts with the unused ferrate" complex to give a deep blue ion combination product (absorption maximum at 658 nm). 

The intense discoloration which developed rapidly upon UV exposure reveals the high photosensitivity of C-PVC that is even more pronounced than for PVC itself, as shown by the UV-visible absorption spectra of figure 5. After 15 minutes of irradiation, large amounts of polyenes have already accumulated in C-PVC, with sequence lengths up to 20 conjugated double bonds, while PVC is hardly affected after that short exposure. 

Figure 5. UV-visible absorption spectra of PVC and C-PVC films before and after 15 min of UV irradiation in a N2 atmosphere...

Figure 9. UV-visible absorption spectra of a stabilized PVC plate, with or without a 70 yin UV cured epoxy-acrylate coating, before and after QUV aging at 40°C...

Electronic spectroscopy, often referred to as UV/visible spectroscopy, is a useful instrumental technique for characterising the colours of dyes and pigments. These spectra may be obtained from appropriate samples either in transmission (absorption) or reflection mode. UY/visible absorption spectra of dyes in solution, such as that illustrated in Figure 2.3, provide important information to enable relationships between the colour and the molecular structure of the dyes to be developed. 

Tautomerism of the Dye. The complete visible absorption spectra were secured for dyed parathion at several pH values in both 20 and 60% ethyl alcohol. These curves are plotted in Figures 9 and 10. The appearance of an isobestic point in both instances indicates that tautomeric forms of the dye are involved (8). 

The nitroxalkylcorrinoids are easy to characterize since they are basically alkyl corrinoids. The u.v.-visible absorption spectra of the nitroxalkylcorrinoids are quite similar to other alkylcorrinoids. The nitroxalkyl cobalamin has a spectrum with Amax at 525,357, and 329nm with relative extinctions of 1.1, 1.2, and 0.65 respectively. Spectra for a number of typical alkylcobalamins have been reported by Firth et al. (121). The corresponding cobinamide has absorption maxima at 455, 428, 360, and 325 nm with relative extinctions of 1.4, 1.0, 0.61, and 0.62 respectively. Aerobic photolysis of these compounds leaves the corresponding aquocobalamin or aquocobinamide. Likewise, addition of cyanide to the nitroxalkylcobinamide in base leaves dicyano cobinamide. 

Polo and Murakami Iha used anthocyanins extracted from jaboticaba (Myrciaria cauliflora Mart) and calafate (Berberis buxifolia Lam) as dyes for DSSCs. [46] The interaction between the dye molecules and Ti02 was identified by comparing the visible absorption spectra of the bare dye in solution with those acquired after dye absorption on the semiconductor a 15 nm red shift indicated the anchorage of the anthocyanin molecules on the Ti02 nanoparticles. The inorganic semiconductor layer was deposited on ITO and the electrolyte employed was I /I3 dissolved in acetonitrile. The photovoltaic cell obtained with the jaboticaba extract gave an IPCE value of 0.2 with a short-circuit current (/sc) of 7.2 mAcm 2, a Voc of 0.5 V and a fill factor of 54%. 

Despite the considerable amount of information that has been garnered from more traditional methods of study it is clearly desirable to be able to generate, spectroscopically characterize and follow the reaction kinetics of coordinatively unsaturated species in real time. Since desired timescales for reaction will typically be in the microsecond to sub-microsecond range, a system with a rapid time response will be required. Transient absorption systems employing a visible or UV probe which meet this criterion have been developed and have provided valuable information for metal carbonyl systems [14,15,27]. However, since metal carbonyls are extremely photolabile and their UV-visible absorption spectra are not very structure sensitive, the preferred choice for a spectroscopic probe is time resolved infrared spectroscopy. Unfortunately, infrared detectors are enormously less sensitive and significantly slower... 

Figure 9 UY-visible absorption spectra of the complexes (22) and (37) in ethanol solution at room...

Figure 25 Comparison of the UY-visible absorption spectra of complexes (22), (24), and (43) in ethanol...

Figure 2.107 (a) UV-visible absorption spectra of 5 x 10 3 M 1,4-benzoquinone (BQ), its radical anion (BQ ) and dianion BQ2 ) in dimethylsulphoxide solution containing 0,5 M tetra-ethylammonium perchlorate, (b) FTIR absorbance difference spectra of 0.02 M 1,4-benzoquinone in dimethylsulphoxide solution containing 0.5 M tetraethylammonium perchlorate. Positive absorbances are due to the 1,4-benzoquinone radical anion (BQ ) and dianion (BQ2 ) recorded at -1.00 V and -1.80 V respectively. Negative absorbances are due to 1,4-benzoquinone (BQ) present at the reference potential +0.1 V. From Ranjith et ai (1990). 

Figure 2. Diffuse reflectance UV-visible absorption spectra recorded as a function of time after the mixing of solid DPB and H0 57ZSM-5 (a) and after of solid DPB and H6 6ZSM-5 (b)...

Figure 2. Visible absorption spectra of solutions of 3 BC MUfor various mole fractions of chloroform in hexane. The spectra are progressively offset by multiples of 5000 Ljmol-cm. The polymer concentration is 1.94 10 s moll L.

Salfeld JC (1972) Ultraviolet and visible absorption spectra of humic systems. In Humic Substances (eds Povoledo D, Golterman HL), Center for Agriculture Publications and Documentation, Wageningen, The Netherlands, p. 269-280... 

The conformational mobility of a chromophoric main-chain polymer is often connected to its electronic structure. Therefore, changes in the UV-visible absorption spectra and/or chiroptical properties are spectroscopically observable as thermo-, solvato-, piezo-, or electrochromisms. It is widely reported that o-conjugating polysilanes exhibit these phenomena remarkably clearly.34 However, their structural origins were controversial until recently, since limited information was available on the correlation between the conformational properties of the main chain, electronic state, and (chir)optical characteristics. In 1996, we reported that in various polysilanes in tetrahydrofuran (THF) at 30°C, the main-chain peak intensity per silicon repeat unit, e (Si repeat unit)-1 dm3 cm-1, increases exponentially as the viscosity index, a, increases.41 Although conventional viscometric measurements often requires a wide range of low-dispersity molecular-weight polymer samples, a size exclusion chromatography (SEC) machine equipped with a viscometric detector can afford... 

The kinetics of three redox processes have been studied for sensitized Ti02 systems where the sensitizers are [Ru(dicarboxy-bpy)2(CN)2], [Ru(dicarboxy-bpy)2(SCN)2], [Os(dicarboxy-bpy)2(CN)2], and [Os(dicar-boxy-bpy)2(SCN)2] (30). The Ru(II) complexes display characteristic excited-state spectra in methanol solution and decay back to the ground state with lifetimes of about 200 ns. For the Os(II) complexes in solution the excited states decay much more rapidly (< 10ns). On the other hand, when these complexes are adsorbed on Ti02 excitation leads to the prompt conversion to the M(III) oxidation state, as indicated by transient visible absorption spectra. These results imply that electron injection from all four of the excited sensitizers into the Ti02 occurs rapidly (< 10 ns). 

In this paper, UV-visible absorption spectra and X-ray diffraction experiments of single crystals and solvent cast films of the azobenzene amphiphiles, CnAzoCmN+Br, were systematically investigated. Structural characterization of the cast bilayer films are discussed in comparison with aqueous solutions and single crystals. Some novel functional properties of the cast films are described, too. We also emphasize that the two-dimensional molecular assemblies, cast films and crystals of bilayer-forming amphiphiles, are suitable candidates for "crystal engineering" because of their simple structures compared with usual three-dimensional molecular crystals. 

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