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The lanthanide-tuned structural and magnetic characterization of magnetic materials based on the use of 2,2':6',2'-terpyridine (terpy) as a blocking ligand at the [Ln.sup.III] center which forms isomorphous cyano-bridged compounds is demonstrated.

[Mn(super III)(salen)(H2O)(super +1)[salen = the N,N' -ethylenebis(salicylideneaminato) dianion], which has a high-spin ground state (S = 2), as a building block is studied. Results suggest the possibility of design and construction of single molecule magnets or high-spin molecules based on Schiff-base cationic precursors and octacyanometalates.

The self-assembly of [NbIV(CN)8]4- with different 3d metal cenfers in an aqueous solution and an escess of pyrazole resulted in the formation of four 3D isostructural compounds {[MII(pyrazole)4]2[NbIV(CN)8] · 4H2O}n, where MII = Mn, Fe, Co, and Ni for 1-4, respectively. All four assemblies crystallize in the same I41/a space group and show identical cyanido-bridged structures decorated with pyrazole molecules coordinated to MII centers. All four compounds show also long-range magnetic ordering below 24, 6, 6, and 13 K, respectively. A thorough analysis of the structural and magnetic data utilizing the molecular field model has allowed for an estimation of the values of coupling constants JM-Nb attributed to the one type of MII-NC-NbIV linkage existing in 1-4. The JM-Nb values increase monotonically from -6.6 for 1 through -3.1 for 2 and +3.5 for 3, to +8.1 cm-1 for 4 and are strongly correlated with the number of unpaired electrons on the MII metal center. Average orbital contributions to the total exchange coupling constants JM-Nb have also been identified and calculated: antiferromagnetic JAF = -21.6 cm-1 originating from the dxy, dxz, and dyz orbitals of MII and ferromagnetic JF = +15.4 cm-1 originating from dz2 and dx2-y2 orbitals of MII. Antiferromagnetic interaction is successively weakened in the 1-4 row with each additional electron on the t2g level, which results in a change of the sign of JM-Nb and the nature of long-range magnetic ordering from ferrimagnetic in 1 and 2 to ferromagnetic in 3 and 4. [ABSTRACT FROM AUTHOR]

The reaction of cetium(lll) nitrate, sodium octacyanotungstate(V), and 2,2'-bipyrimidine (bpm) under vanous conditions leads to the formation of three new compounds: ionic [Ce2(bpm)(dmf)6(H2O)8][W(CN)5]2∙3H2O (1; dmf = N,N- dimethylforrnamide), tetranuclear molecules [Ce2(bpm)(dmso)8(H2O)4][W(CN)8]2∙4H2O (2; dmso = dimethyl sulfoxide), and a two-dimensional inorganic-organic hybrid coordination polymer ([Ce2(bpm)(dmf)8(H2O)2][W(CN)5]2)n-2nH2O (3), allot which contain the subunit [Ce2(u-bpm)] within the structure. These systems were characterized by single-crystal X-ray diffractometry, FTIR spectroscopy, and thermogravimetric analysis. Magnetic susceptibility measurements for 1-3 were performed on polycrystalline samples ot the compounds. Magnetic behavior was interpreted in terms of the ligand-field splitting parameters and the exchange interaction between lanthanide centers and a d-electron spin carrier. The msufts confirmed the ferromagnetic cyano-mediated (Ce-NC-W) interaction kew = 1.7 (2) and 1.4(3) cm-1 (3) compared to the antiferromagnetic (Ce-bpm-Ce) interaction JCeCe = -1.1 cm-1 (1 and 2). [ABSTRACT FROM AUTHOR]