Ni2[LnCl6] (Ln = EuII, CeII, GdII): the first LnII compounds stabilized in a pure inorganic lattice.

Here we report the first examples of 3d-4f compounds based on LnII cations. We have obtained a series of Ni2[LnCl6] isostructural compounds where LnII = Ce 1, Eu 2 and Gd 3 which were characterized in a cubic crystalline system with a Fm3[combining macron]m space group. Magnetic and optical characterization was also performed on this new class of compounds.

catena-Poly[tris(µ3-acetylacetonato)nickelate(II)sodium(I)].

The title complex, [NaNi(C5H7O2)3]n, contains an anionic tris(acetylacetonato)nickelate(II) unit, [Ni(acac)3](-) (acac is acetylacetonate), with a highly regular octahedral coordination geometry. The Ni(II) cation lies on a Wyckoff a site, resulting in D3 symmetry of the anion. Charge balance is provided by sodium cations, which occupy Wyckoff type b sites. Each sodium cation is surrounded by two [Ni(acac)3](-) anions, each of which is connected to the alkali metal through three O atoms, in a fac configuration. This arrangement leads to the formation of linear [Na{Ni(acac)3}]n chains along the c axis. The Ni···Na distance is 2.9211 (10) Å. The title complex is one of the few examples of heterometallic systems based on alkali and transition metal cations bridged by acetylacetonate ligands.

Single crystal electron paramagnetic resonance spectra of Cu(II) ions in Cu(tyrosine)(2): a study of weak exchange interactions mediated by resonance assisted hydrogen bonds (RAHB).

EPR measurements have been performed on single crystals of [Cu(L-tyrosine)(2)](∞) at 33.8 GHz and at room temperature. The EPR spectra display partially resolved EPR lines for most orientations of the magnetic field in the ab plane, and only one resonance for orientations close to the crystal axes, while only a single line is observed along any direction in the ca and cb crystal planes. This behavior is a result of the selective collapse of the resonances corresponding to the four copper sites in the unit cell produced by the exchange interactions between the copper ions. The magnitudes of the exchange interactions between the copper ions were evaluated from the angular variation of the line width and the collapse of the EPR lines. The value |J(AD)/k(B)|=0.8 K between neighboring copper atoms at 4.942 Å is assigned to a syn-anti equatorial-apical carboxylate bridge with a total bond length of 6.822 Å, while the small value |J(AB)/k(B)|=0.004 K is assigned to a long bridge of 11 atoms with a total bond length of 19.186 Å, that includes one resonance assisted hydrogen bond (RAHB). This finding is discussed in terms of values obtained for similar paths in other model compounds and in proteins.