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The synthesis and the magnetic properties of two new bimetallic chromium-vanadium ferrimagnets, compounds 1 and 2, are reported. They belong to a set of nonstoichiometric Prussian blue analogues C I y V-[Cr III (CN) 6 ] z ‚nH 2 O (C, alkali cation) with T C varying between 295 and 315 K (T C ) 310 K for 1 and 315 K for 2). They are obtained through mild chemistry from the molecular precursor [Cr III (CN) 6 ] 3and from vanadium V II salts. The synthetic conditions determine (i) the oxidation state of the vanadium (V II , V III , or V IV ), (ii) the stoichiometry, and (iii) hence the magnetic properties. The reported systems present a larger magnetization than the first reported V-Cr analogue (0.36N A β for 1 and 0.40N A β for 2). Furthermore, X-ray magnetic circular dichroism (XMCD) data demonstrate (i) the short-range antiferromagnetic coupling between the spins borne by the chromium(III) and vanadium ions and (ii) the reversal of the local magnetization on vanadium and chromium when changing the stoichiometry.

Reaction of tris(oxalato)chromium(III) complexes, [Cr III (ox) 3 ] 3-(ox 2-) C 2 O 4 2-), with salts of the trivalent rare earth ions, Ln) La, Ce, Pr, and Nd, generates the polymeric 3d-4f coordination solids with stoichiometries [Ln III Cr III (ox) 3 (H 2 O) 4 ] 2 ‚nH 2 O, n varies from 12 to 7. Results of single-crystal structural analyses of two representative compounds within the isostructural series are discussed. Crystal data: [La III Cr III (ox) 3 (H 2 O) 4 ] 2 ‚ 12H 2 O (1), monoclinic, space group C2, a) 36.080(8) Å, b) 10.906(1) Å, c) 10.935(2) Å,) 105.55(1)°, Z) 4; [Ce III Cr III (ox) 3 (H 2 O) 4 ] 2 ‚12H 2 O (2), monoclinic, space group C2, a) 36.075(6) Å, b) 10.887(1) Å, c) 10.913(2) Å,) 105.65(1)°, Z) 4. X-ray powder diffraction established the isostructurality within the series, and from thermal gravimetry analyses, the number of water molecules of crystallization for the conditioned, polycrystalline samples was determined. The crystal structures assume extended molecular arrays based on two types of symmetrically independent molecular chains with a ladder-type motif. Therein, the metal ions are mutually bridged by three oxalate ligands; thus, the tris-chelated Cr(III) ion has a slightly distorted octahedral environment, whereas the tris-chelated Ln(III) ion is 10-coordinated with four additional water molecules in its coordination sphere. Two other compounds of the same stoichiometry, involving the Eu(III) and Tb(III) ions, are presented. A preliminary study of the magnetic properties of the structurally characterized compounds is reported.

An infinite stair-like layered ferromagnetic system is obtained from the reaction of K3[CrIII(CN)6] with [NiII-(~yclarn)][ClO~]~ (cyclam = 1,4,8,1 l-tetraazacyclotetradecane); a quasi-two-dimensional magnetic behaviour is suggested by the absence of three-dimensional magnetic order down to 2 K.

The synthesis, structural characterization, and magnetic properties of a new Prussian blue analogue, the moleculebased ferrimagnet (V IV O)[Cr III (CN) 6 ] 2/3 ‚ 10 / 3 H 2 O (1) (T C ) 115 K), are presented. The crystal structure is determined from the powder X-ray diffraction diagram using the Rietveld method. The system is cubic, space group Fm3m with cell parameter a ) 10.490(4) Å. The value of the exchange coupling parameter J (-48 cm -1 ) between Cr III and V IV O is estimated from the molecular field parameter W, obtained by fitting the | M -1 | ) f(T) data in the paramagnetic phase of the compound. The dependence of the T C value is analyzed in relation with the connectivity of the molecular precursor, the stoichiometry of the three-dimensional material, and the nature of the constituting metal ions. The T C value of 1 is compared to that of the high-T C ferrimagnet (315 K) V[Cr(CN) 6 ] 0.86 ‚2.8H 2 O (2); the values of the J parameters are almost the same. This allows us to estimate the T C values for other possible vanadium-chromium ferrimagnets.

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The combinations of bisamidium dicationic tectons 1-2H+ and 2-2H+ bearing two OH groups as additional H-bond donor/acceptor sites with [M(CN)6](3-)2 (M = Fe, Co, Cr) anions lead to the formation of robust porous crystals (decomposition temperature in the range of 240-300 degrees C) offering channels occupied by water molecules. The release and uptake of solvent molecules takes place through a reversible single crystal-to-single crystal transformation. Importantly, the temperature of dehydration can be increased by ca 40 degrees C through the decoration of the channels by introduction of OH groups on the backbone of the organic tecton.

The reproducible formation of a 3D oxalate based coordination compound of formula (NH4)5[Mn(II)2Cr(III)3(ox)9]·10H2O, with an unusual Mn(II)/Cr(III) ratio, is presented. The original topology of the anionic network leads to antiferromagnetic long-range ordering whereas its guests favour high humidity-dependent proton conductivity.