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The synthesis, electrochemistry, and magnetism of two novel dimeric, [Fe.sup.3}-containing tungstogermanates is reported. Both polyanions exhibit diamagnetic ground states with a small amount of paramagnetic impurity and have common simultaneous reduction of all of their [Fe.sup.3} centers.

The synthesis, structure, electrochemistry, magnetism of novel cobalt(II)- contain silicotungstate sandwich dimer [{Co(sub 3)(B-beta-SiW(sub 9)O(sub 33)(OH)(B-beta-SiW(sub 8)O(sub 29)(OH)(sub 2)}(sub 2)](super 22-) (1) are discussed. It is believed that the dimeric nature of 1 is maintained in solution as based on gel filtration chromatography.

The prevalent belief about a strong anisotropy of the magnetic exchange in rare-earth compounds, Cs3-Yb2Cl9 and Cs3Yb2Br9 crystals are found to exhibit fully isotropic exchange coupling between Yb(super 3+) ions. An attempt is made to reveal the physical origin of this surprising feature.

The synthesis of trinuclear magnetic building block of Mo3S7(dmit)(sub 3) is described. The potential of Mo3S7 cluster complex paves the way to an entirely new set of molecular conductors and/or magnets.

Research has been conducted on the cubane-like tetranuclear ferrous complexes. The X-ray crystal structure and magnetic properties of these complexes have been investigated and the details are discussed.

Salts containing the dinuclear anion (M(sub.2)Cl(sub.6))(super.2-) (M = Mn, Fe, Co) are discussed relative to magnetic properties, structures and reactivities. The edge-sharing bitetrahedral anion was isolated with 5 different cations. The electronic ground state of the ion is orbitally degenerate and highly anisotropic, a conclusion confirmed with magnetic data. The bridging ligand mediates antiferromagnetic exchange. The D parameter is large and negative. High-spin polynuclear transition metal compounds are of interest for magnetic properties for biological use and for materials chemistry. Iron, or ferrous, compounds have not been studied well vs ferric systems.

Research is presented demonstrating the combined use of an inelastic neutron scattering study with magnetic susceptibility, specific heat and magnetization measurements on a deuterated sample of K10[Co4(H2O)2(PW9O34)2].22H2O, to investigate the ground state properties of a tetranuclear Co2+ cluster.

Research is presented describing the combination of magnetic susceptibility and magnetization measurements with a detailed inelastic neutron scattering study on fully deuterated K6Na4[Ni4(H2O)2(PW9O34)2].24H2O, to investigate the ground-state properties of the tetranuclear Ni2+ cluster [Ni4(H2O)2(PW9O34)2]10-.

Research was conducted to examine the rational synthesis and the structural and magnetic characterization of three different magnetic nickel clusters encapsulated in Keggin trivacant fragments. Magnetic susceptibility, magnetization, electron paramagnetic resonance spectrometry and inelastic neutron scattering spectroscopy were used to measure the energy levels and exchange interactions in the clusters. Results indicate that the polyoxometalate complexes constitute ideal models for the study of the exchange interactions in symmetrical clusters of increasing nuclearities.

A comprehensive theoretical study of the magnetic exchange between Co[sup 2+] ions is reported. Using the microscopic background we deduce the general Hamiltonian for a corner shared bioctahedral system involving kinetic exchange, spin-orbit coupling, and low-symmetry local crystal field. This Hamiltonian acting within the orbitally degenerate ground manifold ([sup 4]T[sub lg])A ⊗ ([sup 4]T[sub 1g])[sub B] of the cobalt pair is expressed in terms of orbital and spin operators. The treatment of the Hamiltonian is performed with the use of the irreducible tensor operator technique. We elucidate the major electronic factors controlling the magnetic anisotropy in the Co(II) pairs. The degree of the exchange anisotropy is shown to depend on the strength of the cubic crystal field and on the relative efficiency of two kinds of electron transfer pathways (e-e and t[sub 2]-t[sub 2]) contributing to the kinetic exchange. An unusual role of spin-orbit interaction is revealed. This interaction tends to reduce the anisotropy caused by the orbitally dependent exchange. Special attention is paid on the topical case when spin-orbit coupling exceeds the exchange interaction. In this case the effective Hamiltonian in its general form is projected onto the subspace of low-lying Kramers doublets and in such a way the pseudo-spin-1/2 Hamiltonian is derived. Unlike the commonly accepted phenomenological approaches based merely on the symmetry arguments the proposed procedure is grounded on the microscopic consideration and hence allows us to establish the interrelation between the idem parameters of the system and the effective parameters of the pseudo-spin-1/2 Hamiltonian. Finally, we discuss the applicability of the conventional Lines' model. [ABSTRACT FROM AUTHOR]

The structure and magnetic properties of the sodium salt of the [[Er[W.sub.10][O.sub.36]].sup.9-] polyanion are described. Polyoxometalates (POM) chemistry has provided ideal examples of lanthanide single-ion single-molecule magnets (SMMs).

The significance of the electron transfer and magnetic exchange interactions in modifying the magnetic properties of the high-nuclearity and high-electron-population, mixed-valence (MV) polyoxovanadate complexes is discussed. The discussed systems are shown to act as the most complex magnetic clusters studied so far.

A series of compounds (cat)[[V.sub.6][O.sub.6][(OC[H.sub.3]).sub.8](calix)(C[H.sub.3]OH)] are obtained under anaerobic conditions and solvothermal reaction of VOS[O.sub.4] with p-tert-butylcalix[4]arene (calix) in methanol by using different types of bases. The analysis of the magnetic behavior of all compounds have shown that the V(III)...V(IV) interactions are weakly ferromagnetic, while the V(IV)...V(IV) are antiferromagnetic.

Three new polynuclear copper (II) complexes of 2-picolinic acid were synthesized and studied using x-ray diffraction analysis. Variable-temperature magnetic measurements showed weak ferromagnetic interaction between the metal centers for all three complexes.

A study was conducted to establish the origin of the strong spin interaction between the two delocalized electrons present in the reduced polyoxometalate decawolframate. The results showed the electron-transfer process to play dominant role compared to magnetic exchange.

A report on the synthesis and the structural and magnetic characterization of a novel heptanuclear cobalt encapsulated in a heteropolyoxotungstate is given. The structural point of view and the magnetic point of view of the results are emphasized.

Research has been conducted on Co (super)2+ ions. The authors discuss the microscopic theory of magnetically anisotropic effective pseudo-spin-1/2 Hamiltonian developed for these ions.

The synthesis of a Cu4(OH)4 cube which is coordinated by four molecules of the dipyridyl ligand 1,6‐[di(pyridin‐4‐yl)hex‐3‐ene] is reported. This compound has a trans double bond which restricts the conformational freedom of the ligand and favours coordination within a unique copper cube. The structure was solved by an X‐Ray single crystal structure determination and low temperature magnetic susceptibility measurements examined its magnetic properties. The cube classification corresponds to the type I classification of Mergehenn and Haase and the short/long distribution of Cu ⋅⋅⋅ Cu separations in the cube as defined by Ruiz. The magnetic susceptibility measurements show paramagnetic behaviour down to 50 K but below this the copper cube shows weak ferromagnetic exchange interactions. The low temperature magnetic susceptibility characteristics are examined in detail then modelled and compared to other similar Cu4O4 copper cubes. [ABSTRACT FROM AUTHOR]

The ground-state properties of the pentameric Co(II) cluster [Co3W(D2O)2(CoW9O34)2](sub 12-) were investigated by inelastic neutron scattering(INS). Spectroscopic techniques are used to determine energy splittings caused by exchange interactions and after this the energy level pattern is reproduced by the eigenvalues of an appropriate effective spin Hamiltonian.

The tetranuclear [Ni4(pypentO)(pym)(mu3-OH)2(mu-Oac)2(NCS)2(OH2)] cubane-like complex is prepared and its structure and magnetic properties are studied. The large differences in magnetic exchange interactions resulting from small differences in Ni-O-Ni angles in this Ni4O4 core of very low symmetry reflect a strong magnetostructural correlation.