Copper complexes spectra

In their pursuit of determining solution structures of dinuclear copper complexes as carried out for complex (29) (Section 6.6.3.1.1). Comba reported complex (431) (r = 0.02 Cu-Cu 6.9 A, comparable with the values of 7.2 A predicted by molecular mechanics calculations and 6.7 A obtained from the simulated EPR spectrum).54 They reported369 complexes (432) (square planar) and (433) (Cu-Cu 3.35 A) as well. As part of studying magnetic properties of mono-, di-, and... 

A typical nitrogen ENDOR spectrum of a copper complex (Cu(sal)2) with two magnetically equivalent 14N nuclei and with the EPR observer at mF = 0 (two sets of six ENDOR lines) is shown in Fig. 9. The pronounced splitting of the lines into a doublet structure is described by the term 4/Jai. The splitting of the more intense lines by 4/ a3 is not resolved (see B5). 

The copper complex Cu(bipyam)2(C104)2 diluted into the corresponding Zn host crystal1055 shows an ENDOR spectrum which is due to four magnetically nonequivalent... 

The blue copper protein stellacyanin, with a molecular weight of about 20,000, is obtained from the Japanese lacquer tree Rhus vemicifera. The EPR spectrum is described by roughly axial g and ACu hfs tensors and an unusually small a j value. As shown in Fig. 39 a, only the largest copper hf value A u can be directly determined from the EPR spectrum202. This coupling does not lie along the largest g-principal axis, in contrast to the usual behaviour of square planar copper complexes. 

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

Jezowska-Bojczuk et al." compared the coordination modes of tobramycin (6) with Cu + with respect to kanamycin B (tobramycin possesses a 3 -H as opposed to the 3 -OH functionality encountered in kanamycin B). The copper complexes of tobramycin formed at various solution pH values were observed to closely resemble those of kanamycin B (Table 8.1). However, the UV-vis spectrum of... 

The other copper-only binuclear centre to be considered is the CuA or purple copper complex. It is part of the terminal oxidase in mitochondrial respiration, cytochrome c oxidase (COX). Its EPR signature, a seven-line spectrum, has since long been known to be different from the classes type 1 to 3 and arises from two copper ions in a 1.5 valence (or mixed valence) state, first proposed from EPR-analysis of a similar center in nitrous oxide (N20) reductase. There is a close correspondence between the blue and purple states of copper since each of the two copper ions in CuA can be considered as being structurally related to the mononuclear blue site coordination. 

Fig. 6. PTI spectra of the copper-dihydrogen acceptors that appear in samples that were grown under atmospheres of different hydrogen isotopes, (a) Pure H2, showing the complex spectrum of A(CuH2) (b) a 1 1 mixture of H2 and D2, showing A(CuH2), A(CuHD), and A(CuD2) in a 1 2 1 ratio (c) nearly pure D2, showing A(CuD2) and a trace of A(CuHD).

Thus, the historical development of the chemistry of metallocorrolates until 1980 includes complexes with Cu2+, Ni2+, Pd2+, Fe3+, Co3+, Rh+, Mo5+ and Cr5+. The palladium complex has been isolated as its pyridinium salt since the neutral species was too unstable to be isolated or spectroscopically characterized [19]. The nickel complex was non-aromatic, with one of the potentially tautomeric hydrogens displaced from nitrogen to carbon in such a way as to interrupt the chromophore. In contrast the electronic spectrum of the paramagnetic copper complex is similar to those of the fully conjugated lV(21)-methyl derivatives [11],... 

Complexes of formazans having one or two carboxylic groups in the 2- or 2,2-positions of the aryl substituents, however, appear to be bicyclic. Thus, a hydrate was obtained on reaction of l,5-bis(2-carboxyphenyl)-3-cyanoformazan with copper acetate [76], The coordinated water could not be removed by drying and produced a broad band in the IR spectrum at 3450 cm-1. The copper complexes of formazans containing carboxyl groups were then assigned the structure 42. 

The d-d absorption of the copper complex differs in each step of the catalysis because of the change in the coordination structure of the copper complex and in the oxidation state of copper. The change in the visible spectrum when phenol was added to the solution of the copper catalyst was observed by means of rapid-scanning spectroscopy [68], The absorbance at the d-d transition changes from that change the rate constants for each elementary step have been determined [69], From the comparison of the rate constants, the electron transfer process has been determined to be the rate-determining step in the catalytic cycle. 

Additional information on the nature of copper complexes formed on the Ti02 surface and their relative amount has been obtained in [285]. Fig. 8.18 represents typical EPR spectra of Cu2+ ions adsorbed onto Ti02 nanoparticles at pH 3.1 and 6.0. At pH 3.1, the spectrum is typical of isolated mononuclear Cu(II) complexes. Some noticeable broadening of the ESR lines corresponding to the parallel orientation of Cu(II) complexes in the external magnetic field, which is observed even for the most magnetically diluted samples, is indicative of the existence of several paramagnetic centers with similar, but not identical structures. The increase of Cu(II) concentration results initially in an increase of... 

Fig. 3. Relationship between width at half-height (AH1/2) of the low-field component of the ESR spectrum of copper complex with poly(hydroxyphenyl-benzoxazolterephthalamide) and the ratio [Cu]/[L] at -196 °C...

Figure 7. Ground-state wave function of plastocyanin. A HOMO wave function contour for plastocyanin (28). B HOMO wave function contour for the thiolate copper complex tet b (34/ C Copper L-edge (38) and sulfur K-edge (34) spectra as probes of metal-ligand covalency. D Absorption, single-crystal polarized absorption, and low-temperature MCD spectra of plastocyanin. The absorption spectrum has been Gaussian resolved into its component bands as in reference 33.

The first example of a chiral copper photosensitizer is [Cu(dmp)((R,R-diop))]+ [R,R-diop = (R,R)-2,3-0-isopropylidene-2,3-dihydroxy-1,4-bis(diphe-nylphosphino)-butane dmp = 2,9-dimethyl-1,10-phenanthroline], in which two chiral centers are introduced in the (R,R)-diop ligand. This complex was applied to the stereoselective photoreduction of [Co(edta)]- [25]. After the reaction, the CD spectrum exhibits a positive peak at 590 nm and a negative one at 515 nm, which indicates the presence of excess A-fCo(edta)]. This means that A-[Co(edta)] more rapidly reacts with the photoexcited copper complex than does the A-enantiomer, where the stereoselectivity, defined as the ratio of the conversion rate, is 1.17. However, the photoreduction of Co(acac)3 and [Co(bpy)3]3+ occurs without stereoselectivity. This is probably because the electrostatic attraction between [Cu(dmp)((R,R-diop))]+ and [Co(edta)] is favorable for the stereoselection, but such interaction does not exist between [Cu(dmp)((R,R-diop))]+ and the other cobalt(III) complexes. 

S-Diketones which contain aliphatic, aromatic, or heterocyclic radicals as well as a selenienyl radical have in the UV spectrum two characteristic absorption maxima (280 and 300 m/a) and high absorption intensity almost equal to that of their copper complexes. In the... 

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