Magnetic ground state properties

The compounds [M(bpy)3][SeCN]3 (M = Ce, Pr, Nd, Tb, Dy, Ho, or Er) have been prepared by the reaction of M(SeCN)3 with bpy (307, 849). Conductivity studies of solutions of the compounds, together with infrared and crystallographic studies of the solids, suggested that a 6-coordinate formulation was appropriate. The ground-state magnetic properties and photophysical properties of the triplet excited states of [M(bipy) ] + complexes (M = Pr, Nd, Tb, Dy, or Er n = 3 or 4) have been reported (872). The complexes are prepared by the reaction of the appropriae metal perchlorates with bpy in ethanol. 

The electronic, magnetic, and vibrational properties of [2Fe-2S] + + clusters have been extensively characterized using the combination of absorption, CD, VTMCD, EPR, ENDOR, Mbssbauer, NMR and resonance Raman spectroscopies, and the ground-state electronic properties are summarized in Figure 3. In the oxidized state, the two 5 =5/2 Fe ions in the [2Fe-2S] + cluster are antiferromagnetically coupled (/ 360 cm for plant-type Fds and >550 cm for... 

The magnitude of the separation between the adjacent states of a term indicates the strength of the spin-orbit coupling, and in all but two cases (Sm and Eu ) it is sufficient to render the first excited state of the Ln ions thermally inaccessible, and so the magnetic properties are determined solely by the ground state. It can be shown that the magnetic moment expected for such a situation is given by ... 

We have investigated ground state properties on a first principles basis. Total energy as well as magnetic moment (for FeaNi) were determined with the FLAPW method and the GGA introduced by Perdew and Wang in 1992 by employing the WIEN95 code developed by Blaha et al. 

That magnetic measurements often raise more problems than they solve, is demonstrated for the indicated compound. We prepared a series of [ (C2H5N] i,An(NSC) e compounds (An = Th, U, Np, Pu) with cubic coordination of the actinide ion. We derived a consistent interpretation of the magnetic and optical properties of the uranium and the neptunium compounds (6 ). In the case of Pu we expect an isolated T1 ground state and a first excited state at about 728 cm-1. To our surprise we found a magnetic ground state much more pronounced than in the case of the hexachloro-complex, Fig. 4. 

Although magnetic properties of a number of plutonium compounds are known, it seems from the above discussion that the knowledge of the electronic ground state properties is very limited. Each compound represents a system of its own which has to be... 

---