Copper hyperfine tensor

Even more challenging than the determination of the g-tensor is the calculation of the copper hyperfine tensor since it has large contributions from three terms of... 

Copper porphyrin is one of the best-characterized of the metalloporphyrins, and its electron spin resonance (ESR) spectrum has been known for a quarter of a century.(17) More recently, electron nuclear double resonance (ENDOR) investigations have provided the complete hyperfine tensors for the metal, the nitrogens and the pyrrole protons.(18) We have used this detailed knowledge earlier(, ) to assess the quality of scattered-wave calculations. 

In those calculations, the contributions from electronic orbital motion (induced by spin-orbit mixing) were estimated from crystal field theory (for the copper atom) or were neglected (for the nitrogen and hydrogen atoms). Here I discuss for the first time direct calculations of these contributions to the copper and nitrogen hyperfine tensors, as well as to the molecular -tensor. 

The ESR spectra of copper(ll) bis(dithiocarbamate) complexes has been widely discussed in previous reviews (16, 17). A number of more recent contributions have been made (72, 121, 129, 316, 477, 1680-1683). These include work by Bereman and Nalewajek (72), who have analyzed the ESR spectra of indole, indoline, and carbazole-derived dithiocarbamate complexes. Their results suggest a strong covalency in the in-plane a-bonding and moderate covalency for the in-plane and out-of-plane 7t-bonding. The latter indicates that these dithiocarbamate complexes exhibit a strong predominance of the non-thioureide resonance form, and it is this which is the strong-field form for dithiocarbamates (see Section III.C). The covalent nature of the copper-sulfur bonds has been confirmed by calculations, which also reveal that the odd electron is delocalized over the CUS4 unit, and lead to theoretical values for the g-tensor and copper and sulfur hyperfine tensors (1684). 

The shape of the H NMRD profiles can be very different according to the different values of Aj, A and the position of the proton with respect to the molecular frame defined by the hyperfine A tensor. As an example, the H NMRD profiles of the copper(II) protein superoxide dismutase are shown in Fig. 5.38 for... 

Fig. 4.7 Anisotropic ESR spectra of monovalent copper complex in frozen toluene solution, (a) 2 mm band ESR (140 GHz), (b) 3 cm band ESR (9.6 GHz) experimental spectnim, (b ) simulated spectrum with g = (2.0078, 2.0059, 1.9991), A(P ) = (20, 23, 20) G, A(P) = (8, 11, 8) G, and A(Cu) = (20, 0, 17) G for the principal values of the g-tensor and hyperfine coupling tensors of two inequivalent phosphorous and one Cu atom. The spectra are adapted from [R.R. Rakhimov et al. Chem. Phys. Letters 255, 156 (1996)] with permission from Elsevier...

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