Copper absorption spectra

Figure 2.4. UV-vis absorption spectrum of 2.4e in water at concentrations of copper(Il)nitrate varying between 0 and 10 mM.

The equilibrium constants obtained using the metal-ion induced shift in the UV-vis absorption spectrum are in excellent agreement with the results of the Lineweaver-Burke analysis of the rate constants at different catalyst concentrations. For the copper(II)ion catalysed reaction of 2.4a with 2.5 the latter method gives a value for of 432 versus 425 using the spectroscopic method. 

Unfortunately, addition of copper(II)nitrate to a solution of 4.42 in water did not result in the formation of a significant amount of complex, judging from the unchanged UV-vis absorption spectrum. Also after addition of Yb(OTf)3 or Eu(N03)3 no indications for coordination were observed. Apparently, formation of a six-membered chelate ring containing an amine and a ketone functionality is not feasible for these metal ions. Note that 4.13 features a similar arrangement and in aqueous solutions, likewise, does not coordinate significantly to all the Lewis acids that have been... 

Whereas ATR spectroscopy is most commonly applied in obtaining infrared absorption spectra of opaque materials, reflection-absorption infrared spectroscopy (RAIRS) is usually used to obtain the absorption spectrum of a thin layer of material adsorbed on an opaque metal surface. An example would be carbon monoxide adsorbed on copper. The metal surface may be either in the form of a film or, of greaf imporfance in fhe sfudy of cafalysfs, one of fhe parficular crysfal faces of fhe mefal. 

Figure 1. X-ray absorption spectrum of a silica supported ruthenium-copper catalyst at 100 K In the vicinity of the K absorption edge of ruthenium. Reproduced with permission from Ref. 8. Copyright 1980, American Institute of Physics.

Figure 19. In situ X-ray absorption spectrum for a copper upd monolayer on a gold (111) electrode with the polarization of the X-ray beam being perpendicular (A) or parallel (B) to the electrode surface.

FIGURE 6.1 Integration of an EPR spectrum. The EPR derivative spectrum of the hydrated copper ion (trace A) is numerically integrated to its EPR absorption spectrum (trace B) and a second time integrated (trace C) to obtain the area under the absorption spectrum. Note that both the derivative and the absorption spectrum start and end at zero, while the doubly integrated spectrum levels off to a constant value the second-integral value. 

Figure 2.73(a) shows the X-ray absorption spectrum of copper. The K edge is the minimum energy required to ionise an electron from the Is orbital ... 

Figure 2.73 (a) The X-ray absorption spectrum of copper showing the K- and L-absorption edges, (b) The K.-edge in more detail. From A.R. West, Solid State Chemistry and its Applications, John Wiley and Sons, Chichester (1984). Reprinted by permission of John Wiley and Sons, Ltd. 

Type I copper enzymes are called blue proteins because of their intense absorbance (s 3000 M-1 cm- ) in the electronic absorption spectrum around... 

FIGURE 7.13 The absorption spectrum, visible region, of a copper sulfate solution. 

FIGURE 7.14 The absorption spectrum, in a narrow portion of the ultraviolet region, of gaseous copper atoms. 

Figure 11.10 Absorption spectrum of the protein-copper complex of the biuret reaction.

Furthermore, the preparation and reactions of 2-methoxythiophene were studied by Sice (70). This compound was obtained by a copper catalysed Williamson synthesis. It was also found that iodothiophene reacted readily with sodium alkoxides, whereas bromothiophene reacted slowly and chlorothiophene did not react at all. Sodium iodide accelerated the reaction of bromothiophene. The ortho, para orienting alkoxy group on carbon atom 2 increased the directive influence of the sulphur atom to the 5 position but competed with it to induce some attack on the 3 position by electrophilic reagents (nitration, acylation). The acylation of 2-methoxythiophene with stannic chloride at low temperatures furnished a mixture of two isomers. The 5-methoxy-2-acetothienone was obtained in higher yield and was identified by its ultraviolet absorption spectrum. 

Characterization of the Type 2 Depleted Derivative of Laccase. The model for the coupled blnuclear copper site in hemocyanln and tyrosinase (Figure 7) may now be compared to the parallel site in laccase which contains a blue copper (denoted Type 1 or Tl), a normal copper (Type 2, T2), and a coupled binuclear copper (Type 3, T3) center. As shown in Figures 8a and b, native laccase has contributions from both the Tl and T2 copper centers in the EPR spectrum (the T3 cupric ions are coupled and hence EPR nondetectable as in hemocyanln), and an intense absorption band at associated with the Tl center (a thlolate —> Cu(II) CT transition).(14) The only feature in the native laccase spectra believed to be associated with the T3 center was the absorption band at 330 nm (e 3200 M cm ) which reduced with two electrons, independent of the EPR signals.(15) Initial studies have focussed on the simplified Type 2 depleted (T2D) derlvatlve(16) in which the T2 center has been reversibly removed. From Figure 8 the T2 contribution is clearly eliminated from the EPR spectrum of T2D and the Tl contribution to both the EPR and absorption spectrum remains. 

ON(SO,)j /0N(S03)2 - redox couple, 33 106 O—O bond, copper proteins, 39 26 homolytic cleavage, 39 60, 62-63 Opposite-spin correlation, 38 439-440 Optical absorption spectrum cytochrome b, 36 418, 420 holoferritin, 36 418-419 Optical centers, interaction with surroundings, 35 319-322... 

The monochromatic X-ray was obtained by silicon (111) channel cut double crystal using white X-ray (at Beam Line 4A (PF)). The ion chambers were set at the both side of the photoacoustic cell, in order to compare the sp trum of photoacoustic X-ray absorption spectroscopy (PAXAS) with usual absorption spectrum, simultaneously. The chopper at chopping frequency of 10 Hz was t at the up-stream of these detectors. Copper foil (5 pm thick) was used as a sample. 

Figure 11 shows the PAXAS spectrum and the absorption spectrum of the copper sample. Quite corresponding fine structure shows that the information of EXAFS is also included in the PAXAS spectrum. The heat generation process also reflects the EXAFS. The only difference is the monotonous increasing trend of PAXAS signal intensity along with the photon energy increase. This is also seen in the previous... 

Fig, 11. Photoacoustic X-ray absorption spectrum and X-ray absorption spectrum for copper foil (5 pm thick). Photoacoustic signal is normalized by ion chamber current. Chopping frequency 10 Hz. Ring current 145-142 mA... 

Nearly monodisperse TOPO-capped copper sulfide nanocrystals of ca. 4.5 nm diameter have been synthesized from [Cu(S2CNMe( Hex))2]. The absorption spectrum of the (CU2S) nanoparticles shows a large blue shift (2.09 eV) in relation to bulk CU2S (1022 nm, 1.21 eV) [225]. 

J. J. van Laar has shown how the form of the vap. press, curves of a liquid mixture can furnish an indication, not a precise computation, of the degree of dissociation of any compound which maybe formed, on the assumption that the different kind of molecules in the liquid—12, Br2, and IBr—possess partial press, each of which is equal to the product of the vap. press, of a given component in the unmixed state and its fractional molecular concentration in the liquid. It is assumed that in the liquid, there is a balanced reaction 2IBr I2-)-Br2, to which the law of mass action applies, where K is the equilibrium constant, and Clt C2, and C respectively denote the concentration of the free iodine, free bromine, and iodine bromide. From this, P. C. E. M. Terwogt infers that at 50 2°, K for the liquid is 7j and that for iodine monobromide about 20 per cent, of the liquid and about 80 per cent, of the vapour is dissociated. That the vapour of iodine monobromide is not quite dissociated into its elements is evident from its absorption spectrum, which shows some fine red orange and yellow lines in addition to those which characterize iodine and bromine. In thin layers, the colour of the vapour is copper red. 0. Ruff29 could uot prove the formation of a compound by the measurements of the light absorption of soln. of iodine and bromine in carbon tetrachloride. 

---