Complexation electronic absorption spectroscopy

Resonance Raman (RR) spectroscopy provides information about the vibrational characteristics of a chromophore, for example, a metal center, within the complex environment of a protein. In RR spectra, those vibrational transitions are observed selectively that are coupled to electronic transitions. In iron sulfur proteins, this technique has been used to resolve the complex electronic absorption spectra and to identify both vibrational and electronic transitions. 

The purity of the terminal Au-oxo complexes, 3 and 4, was established by several methods including P NMR (3 and 4 have only one phosphorus peak at —8.55 and —13.15 ppm, respectively), cyclic voltammetry, electronic absorption spectroscopy, vibrational spectroscopy, detailed magnetic measurements and elemental analysis on all elements (triplicate analyses for Au) (44). The single peak in the PNMR spectra is consistent with the C2V symmetry of 3 and 4 established by multiple X-ray crystallographic structure determinations and a neutron diffraction study on 3 at liquid He... 

Appleby, D., Hussey, C.L., Seddon, K.R., Turp, J.E., Room-temperature ionic liquids as solvents for electronic absorption spectroscopy of halide complexes. Nature, 323,614-615,1986. 

X6]2- with L-L. The trans-dioxo complexes were characterized by IR, H NMR, and electronic absorption spectroscopies (209). 

Low-spin complexes have a 3A ground state and are all diamagnetic. The spectroscopic technique most widely used to investigate their electronic structures is electronic absorption spectroscopy. In the following subsections we will consider some applications of this spectroscopic technique. 

In electronic absorption spectroscopy, we are interested in a transition from the ground state Pg to an excited state e that is allowed by the transition moment operator M that derives from the interaction of the electromagnetic radiation of the photon with the electron in a metal complex (Figure 1.2). 

The electronic absorption spectroscopy of charge transfer (CT) complexes of donor molecules of n-, n- and cr-type (DX) with jt- and rr-acceptors (A = TCNE, I2 etc.) allows one to study the influence of the X substituents bonded to a donor centre, D, on the energies of charge transfer bands, hvcr129- The hvcr and Ip parameters are connected by a linear dependence given in equation 19. 

For the complex [ (bpy)2Ru 2(p.-adc)]3+ (38), researchers invoked a contribution of resonance form II to the ground state in order to explain ESR and electronic absorption spectroscopy results. Alternatively, if Ru orbitals closely match the energy of the LUMO of the bridging ligand, the following resonance forms may result ... 

The electronic structure of transition metal clusters is difficult to probe by electronic absorption spectroscopy, which has proved so fhiitful in revealing the d orbital orderings of classical complexes, because of the multiplicity of overlapping absorption bands. The one-to-one correlation between occupied orbitals and PE bands means that PES can give valuable information on the smaller clusters. The information obtained has given support to the semiempirical theoretical treatments of this class of molecules. 

Coupled techniques have increased in popularity in recent years. Electrochemical techniques can be coupled to another characterization method to provide unique information. Many electrochemical techniques lend themselves well to coupling with other electrochemical or nonelectrochemical techniques. With these methods, cell design is often complex to allow simultaneous execution of both techniques. For example, optically transparent indium tin oxide is used as the working electrode with an optically transparent mesh electrode to allow for simultaneous electrochemical conversion and electronic absorption spectroscopy. For some techniques the sample is electrolyzed and then transferred under inert atmosphere for analysis. 

Electronic Absorption Spectroscopy. Theoretical considerations of the light absorption spectra of /3-carotene (189) and related polyenes have been presented.A method has been devised for describing the shapes of the absorption spectra of polyenes such as -carotene and retinyl acetate as lognormal distribution curves.A new absorption band is seen in the spectrum of jS-carotene acting as electron donor in charge-transfer complexes.The triplet-triplet... 

Mononuclear complexes, [Ru(NH3)5(LH)]2+, where LH = Me2dicydl I, dicydl I and Cl2dicydH, have been prepared and characterized by electronic absorption spectroscopy and cyclic voltammetry.40 When deprotonated, the complexes oxidize to the Ru17 oxidation state and this allowed a spectroscopic analysis the RuIV-cyanamide chromophore. Only [Ru(NH3)5(Me2dicyd)]2+ could be isolated with sufficient purity to permit NMR studies, which suggested the metal ion was diamagnetic RuIv. 

Other Degraded Carotenoids Carotenoid-Protein Complexes Physical Methods Separation and Assay N.M.R. Spectroscopy Electronic Absorption Spectroscopy Resonance Raman Spectroscopy X-Ray Structures Linear Dichroism... 

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