Spin Hamiltonian parameters for

Table 5.1 shows the spin Hamiltonian parameters for some of the complexes. The equilibrium constants and rate constants are given in Table 5.2. 

The EPR spectrum is a reflection of the electronic structure of the paramagnet. The latter may be complicated (especially in low-symmetry biological systems), and the precise relation between the two may be very difficult to establish. As an intermediate level of interpretation, the concept of the spin Hamiltonian was developed, which will be dealt with later in Part 2 on theory. For the time being it suffices to know that in this approach the EPR spectrum is described by means of a small number of parameters, the spin-Hamiltonian parameters, such as g-values, A-values, and )-values. This approach has the advantage that spectral data can be easily tabulated, while a demanding interpretation of the parameters in terms of the electronic structure can be deferred to a later date, for example, by the time we have developed a sufficiently adequate theory to describe electronic structure. In the meantime we can use the spin-Hamiltonian parameters for less demanding, but not necessarily less relevant applications, for example, spin counting. We can also try to establish... 

Spin Hamiltonian Parameters for d5 Ions in Weak Crystal Fields °... 

Spin Hamiltonian Parameters for d1 Ions in Strong Crystal Field... 

Table 38 Spin-Hamiltonian Parameters for Vanadyl Complexes...

Comparison of the Computed and Observed 253 458 Triplet State Electron Spin Resonance Spin Hamiltonian Parameters for Thymine11... 

When these experiments were repeated, in the absence of air, it was discovered that the intensity of the ESR signal due to the Ag11 species almost doubled.539 Reexamination of the reaction for R = Bun showed that further oxidation to a red, diamagnetic Ag complex occurred in air or with excess thiuram disulfide and this accounted for the decrease in signal intensity.540 Values of spin Hamiltonian parameters for some silver(II) complexes are given in Table 67.539-542... 

Studies of the spectra of the homologous Au(R2Dtc)2 complexes have been reported however, it appears that the analyses of the spectra are hampered by the large influence of the quadrupolc moment of the gold nucleus (564, 606, 608). The interpretation of experimentally determined spin Hamiltonian parameters for the Ag(II) and Cu(Il) complexes in terms of LCAO coefficients and... 

Silver(n) and Silvery hi).—The cationic complex bis-(2,2, 2"-terpyridyl)Ag2+ has been isolated as its peroxydisulphate salt.217 The presence of a d-+d band at 15600 cm-1 is indicative of a six-co-ordinate ion. X-ray photoelectron spectra have provided Ag(3d5/2>3/2) binding energies for this complex and the mono-terpy complex. The influence of pyridine and 2-, 3-, and 4-picoline on bis(diethyl dithio-carbamato)AgH has been examined by e.s.r. spectroscopy.218 The results indicate formation of mono-addition products and the spin hamiltonian parameters for these complexes have been determined. 

Forbes, C. E. (1983) Analysis of the spin hamiltonian parameters for Cr3+ in mirror and inversion symmetry sites of alexandrite (Al Cr BeO,). Determination of the relative site occupancy by EPR. J. Chem. Phys., 79, 2590-5. 

The spin hamiltonian parameters for tetragonal C0A4B2 complexes are shown in Fig. 24. As was already stated in section 3, the g and A values are essentially determined by the e values for the axial and equatorial ligands. 

Semi-empirical and ab-initio studies of similar systems have led to less accurate predictions1"312-3141. Observed and calculated d-electron transition energies together with spin Hamiltonian parameters for copper(II) tetraamines are listed in Table 10.7. The accuracy of these predictions is comparable with that obtained for the hexaamines in Table 10.6, and the trends expected for bond length and angular distortions are well reproduced (see above). 

Table III. Spin Hamiltonian Parameters for Liganded and Non-Liganded Native and Modified Galactose Oxidase0...

Spin Resonance Spin Hamiltonian Parameters for Thymine ... 

An extensive account of the theory of the Spin Hamiltonian parameters for low spin Co(II) complexes has been given hy McGarvex (50). This approach is based on third order perturbation theory, involving all excited states giving a spin-orbit contribution to the I az + b(x - y ), Aj), or the yz, A2) ground state respectively. The formulae obtained for the g and A tensors in case of non axial symmetry depend upon a large number (12) of adjustable parameters, and a judicious choice of assumptions is required to make use of these equations. A simpler approach is therefore indicated. 

A question of recent interest is whether the two iron sites in each molecule are equivalent (58), Mossbauer effect studies (28) and ESR studies (59) of human serum transferrin could detect no difference in the spectra of the two iron sites, but recently a very careful study by Aasa (27) has shown small differences in the ESR spectrum due to a small change in the ESR parameter A. The Mossbauer data were shown to be in good agreement with a calculation by Spartalian and Oosterhuis (28) and more recently by Tsang, Boyle and Morgan (60). The spin Hamiltonian parameters for each experimental study are presented in Table 4. 

Table 4. Spin hamiltonian parameters for some 6S iron complexes... 

Table 1 Spin-Hamiltonian parameters for Ni in different systems...

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