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effects on spin-spin couplings. Apparently, even for relatively weak hydrogen bonding, the contribution from "direct" interactions is of the same order of magnitude as the "dielectric"effect.

The electronic origin of the influence of the anomeric effect (negative hyperconjugative interaction, NHI) on the Fermi contact (FC) term of 'J(C,H) couplings has been studied from a theoretical point of view a t the DFT-B3LYP level. The HN=CH, molecule was chosen as the primary model compound, in which both F C 'J(C,H) couplings were decomposed into bond contributions with the natural J coupling dissection approach (NJC). Differences between the I J ( c , H )~~ couplings for C-H bonds in synperiplanar and antiperiplanar orientations with respect to the nitrogen non-bonding electron pair closely follow the experimental trend. They are made up chiefly of three NJC contributions: 'bond', 'direct lone pair' and the 'carbon-core orbitals'. The NHI influence on these terms was studied by applying the natural bond orbital (NBO) deletion procedure to the charge transfer interaction into the antiperiplanar (C-H) antibond (n(N)+(C-H)*) prior to the NJC dissection calculation. The dielectric solvation effect on both the total F C terms and the respective NJC contributions was estimated by carrying out the calculations using the polarization continuum model. Inhibition of the anomeric effect is evident when the solvent polarity is increased. NHI saturates rapidly with increasing solvent dielectric. Specific solute-solvent interaction effects on I J(C,H) couplings were estimated by evaluating molecular complex models of the form CH2=HN. . .S (S = H 2 0 and DMSO).

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We describe nuclear orientation experiments performed on dilute alloys of PdCo. Assuming the proportionality between the hyperfine field and the magnetization, we show that the Co impurity is in a Kondo-like state at low temperatures (T < 100 mK). We discuss the link between the Co positive hyperfine field and its weak Kondo coupling.In the palladium lattice, Mn, Fe, and Co impurities polarize strongly the palladium atoms. Usually, these giant moments are described by a ferromagnetic exchange coupling between the spin S of the impurity and the spin s of the conduction electron.