The reaction of Ln(NO3)3.aq with K3[Fe(CN)6] or K3[Co(CN)6] in N,N'-dimethylformamide (DMF) led to 25 heterodinuclear [Ln(DMF)4(H2O)3(mu-CN)Fe(CN)5].nH2O and [Ln(DMF)4(H2O)3(mu-CN)Co(CN)5].nH2O complexes (with Ln = all the lanthanide(III) ions, except promethium and lutetium). Five complexes (Pr(3+)-Fe3+), (Tm(3+)-Fe3+), (Ce(3+)-Co3+), (Sm(3+)-Co3+), and (Yb(3+)-Co3+) have been structurally characterized; they crystallize in the equivalent monoclinic space groups P21/c or P21/n. Structural studies of these two families show that they are isomorphous. This relationship in conjunction with the diamagnetism of the Co3+ allows an approximation to the nature of coupling between the iron(III) and the lanthanide(III) ions in the [Ln(DMF)4(H2O)3(mu-CN)Fe(CN)5].nH2O complexes. The Ln(3+)-Fe3+ interaction is antiferromagnetic for Ln = Ce, Nd, Gd, and Dy and ferromagnetic for Ln = Tb, Ho, and Tm. For Ln = Pr, Eu, Er, Sm, and Yb, there is no sign of any significant interaction. The isotropic nature of Gd3+ helps to evaluate the value of the exchange interaction.

We present here a detailed structural comparison, both in the solid state and in aqueous solution, of a complete series of lanthanide cryptate complexes of a Schiff base axial macrobicyclic ligand L of general formula [LnL]-[NO 3 ] 3 ‚xH 2 O (Ln ) La-Lu, Y); the macrobicyclic receptor L is an azacryptand N[(CH 2 ) 2 NdCH-R-CHdN-). The crystal structures of the Ce, Nd, and Eu complexes, chemical formulae [CeL(NO 3 )](NO 3 ) 2 ‚1.5H 2 O‚0.5CH 3 CH 2 OH (3), [NdL(NO 3 )](NO 3 ) 2 ‚3H 2 O (5), and [EuL(NO 3 )](NO 3 ) 2 ‚H 2 O‚ CH 3 OH (7), as well as that of [YL(NO 3 )][Y(NO 3 ) 3 (H 2 O) 2 EtOH](NO 3 ) 2 .EtOH‚CH 3 CN (16), have been determined by single-crystal X-ray crystallography. The four crystals crystallize in the triclinic space group (14)°for 16. In light of their crystal structures, it can be stated that all of them adopt very similar structures, with the nine-coordinated metal ion bound asymmetrically to seven donor atoms in the ligand cavity and also to two oxygen atoms of a bidentate nitrate anion. The macrobicycle cavity adapts to the lanthanide contraction, while preserving the pseudo-triple-helix conformation around the metal ion. The coordination geometry of the metal atom is best considered as a slightly distorted monocapped dodecahedron. The aqueous solution structures of the paramagnetic complexes were thoroughly characterized from the proton NMR LIS and LIR data, with particular attention to the changes induced by the lanthanide contraction, and agree quite well with the crystal structures of the Nd and Y complexes. The experimental Ln-donor distances decrease progressively along the lanthanide series both in the solid and solution structures, but no drastic structural changes occur. The gradual contraction and distortion of the coordination polyhedron along the series cause a variation of the crystal field parameter A 2°< r 2 > and the hyperfine constants A i of the lanthanides in the middle of the series, leading to "breaks" in the contact-pseudo-contact shift separation plots of the proton LIS values. However, this affects only slightly the geometric terms G i of the protons and not at all their R ik ratios. The conformational rigidity of the five-membered chelate rings formed by the metal-bound ethylenediamino moieties of the bound cryptand increases upon lanthanide contraction. The ∆G q value for the δ T λ conformational interconversion process of those rings is 70 ( 3 kJ for the Y complex. (1) Alexander, V. Chem. ReV. 1995, 95, 273. (2) Guerriero, P.; Tamburini S.; Vigato P. A. Coord. Chem. ReV. 1995, 139, 17. (3) Sabbatini, N.; Guardigli, M.; Lehn, J. M. Coord. Chem. ReV. 1993, 123, 201. (4) The term axial macrobicycle describes symmetrical molecules with coaxial arrangement of two tripodal subunits linked by three identical bridges. See: Lehn, J.-M.

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Three new polynuclear Mn II complexes with chloroacetate bridges were obtained and characterized by X-ray diffraction: [Mn 3 (µ-ClCH 2 COO) 6 (bpy) 2 ] (1), [Mn 2 (µ-ClCH 2 COO) 2 -(phen) 4 ](ClO 4 ) 2 (2), and [Mn(µ-ClCH 2 COO) 2 (phen)] n (3). The Mn···Mn distance for 1 (3.624 Å ) is smaller than for 2 (4.613 Å ) and 3 (4.530 Å ); this is in agreement with the number of carboxylate bridges. The three compounds show a weak antiferromagnetic coupling. The J values are −3.82 cm −1 for