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The synthesis, X-ray structures, and magnetic properties of a family of [[M.sub.14][(L).sub.6][O.sub.6][(OMe).sub.16][X.sub.6]] cluster where (M = [Fe.sup.III], [Cr.sup.III] and [V.sup.III/IV]) is reported.

Single-molecule magnets with larger spins are generated when the carboxylate ligation is altered by the oxime moiety. The oxime moiety is twisted, due to which there is structural distortion to the core of the molecule that enhances the magnetism of the molecule.

The syntheses, crystal structures and magnetic characterizations of three new hexanulear iron(III) compounds are reported. The large difference in ground state spin was identified as resulting from a single structural difference between the two types of complexes, and the magnetostructural correlation was established between the J values and both the Fe-O bond distances and the Fe-O-Fe angles at the bridging ligands.

Research describes the synthesis, X-ray structure, and analysis of the dodecanuclear title complexes as well as their magnetochemical testing of the solvation dependence of the properties of the title complex, which is a single-molecule magnet.

The use of methylene-bridged calix[4]arenes in 3d/4f chemistry which produces a family of clusters of general formula [[Mn.sup.III.sub.4][Ln.sup.III.sub.4][(OH).sub.4][(C4).sub.4][(N[O.sub.3]).sub.2][(DMF).sub.6][([H.sub.2]O).sub.6]](OH)2 (where C4 = calix[4]arene and Ln = Gd , Tb, Dy) is demonstrated. The replacement of the isotropic [Gd.sup.III] ions with the anisotropic [Tb.sup.III] and [Dy.sup.III] ions 'switches' the magnetic properties of the cluster to make the complexes Tb and Dy to behave as low-temperature molecular magnets and could be applied as an excellent magnetic refrigerant for low-temperature applications.

The article presents the structural and magnetic characterization of the various complexes of [Mn.sub.6] family based on the Single-Molecule Magnets (SMMs).

Study is presented to describe the syntheses, structures and magnetic properties of three Mn wheels which belong to the third category of compounds, unusual [Mn16] and [Mn22] clusters formed from self-assembled 'rodlike and sheetlike' moieties. These complexes are high spin molecules that behave as single molecule magnets (SMMs).

The syntheses, structures and magnetic properties of two new and unusual anionic heptametallic [[Mn.sub.6.sup.III][Mn.sup.II]] bitetrahedra featuring the Et-[sao.sup.2-] ligand are presented. The results have shown that structures can be isolated with different central divalent metal ions in order to create a family of novel heterometallic single-molecule magnets (SMMs).

The deliberate structural distortion of a [Mn.sub.6] compound via the use of a bulky salicylaldoxime derivative switches the intra-triangular magnetic exchange from antiferromagnetic to ferromagnetic resulting in an S=12 ground state and an anisotropy barrier. This suggests that the intelligent use of ligands that can cause targeted distortions to the core structures of [Mn.sub.6] clusters may prove to be viable means to raise the blocking temperatures of SMM to record values.

The microwave-assisted synthesis of [Ni.sub.3] and [Co.sub.3] complexes that could not be synthesized under ambient or solvothermal conditions is demonstrated. The synthesis of stable high-spin [M.sup.II] carboxylate triangles similar to the well-known [M.sup.III] basic carboxylates achieved via the use of microwave heating could provide cluster chemists with a new, fast, and powerful synthetic tool in the search for novel coordination compounds.

The reactions of tripodal alcohols such 1,1,1-tris(hydroxymethyl)ethane ([H.sub.3]thme) directs the formation of heptanuclear cobalt metallocycles in which the metal ions are coupled ferromagnetically. The study of such reactions is extended to two new ferromagnetic clusters whose structures are based on centered hexagons.

The use of tripodal alcohols leads to the synthesis of a small family of hexanuclear, mixed-valent, rodlike Mn complexes whose structures are based on edge-sharing triangles. Despite the structural similarities, their magnetic behavior ranges from diamagnetic ground state to single-molecule magnetism, and this allows examining the effect that subtle changes in geometry have on the nature of the individual pairwise exchange interactions that govern the resultant ground states.

The unexpected formation of a highly reduced vanadium(III/IV) polyoxovanadate is reported. The complex is remarkable because it is based on a square-prismatic, boxlike cluster of oxovanadium(IV) and the oxovanadium(IV) 'box' contains a covalently bound vanadium(III) dimer to give an overall very highly reduced polyoxovanadate.

The microwave-assisted reaction of Fe(O2CMe)2 with salicylaldoxime (saoH2) in pyridine produces an octametallic cluster in crystalline form in 2 min. The core describes a cube encapsulated in a tetrahedron, while [sao.sup.2-] exhibits a novel coordination mode.

The use of microwave heating has improved the reaction rate, enhanced the yield of an inorganic complex, and allowed for the high-temperature/high-pressure synthesis of a [Mn.sup.III] single-molecule magnet. The use of microwave heating is a new, appealing approach for the synthesis of large polymetallic transition-metal cluster compounds and this clearly has enormous potential.

An extension of the methodology in the preparation and characterization of an enneanuclear manganese complex is discussed. Reaction of [Mn3O(O2CMe)6 with the tripodal ligand H3thme (1,1,1-tris(hydroxymethyl)ethane) produces the complex [Mn9O7(O2CCH3)11(thme)(py)3(H2O2)] whose mixed-valent metallic skeleton describes part of an idealized icosahedron.

The use of tripodal ligands in the synthesis of polynuclear clusters of 3d transition metals is investigated. The synthesis and magnetic properties of a family of high-spin Mn clusters built using tripodal ligands, where the directed M3 units edge-share to form structures based on rods is reported.

Theoretical evaluation of the exchange coupling constants present in structurally related Fe8 and Fe16 wheels is in excellent agreement. Calculations show that the exchange is dominated by antiferromagnetic coupling in dinuclear metal units bridged by a combination of alkoxide and carboxylate ligands.

The synthesis and magnetic properties of a new [Mn22] cluster that has a metal oxygen core described as wheel-like single-molecule magnet made from the reaction of Mn(super III) triangle with the tripodal ligand 1,1,1-tris(hydroxymethyl)propane (H(sub 3)tmp) is described. Result shows that the complex is a 3d transition metal cluster containing 22 metal centers and it is the fourth largest Mn cluster behind [Mn 26], [Mn 30], and [Mn 84].

The formation of octametallic and tridecametallic clusters from the reaction of MnF3 with 5, 6-dimethylbenzotriazole in hot MeOH is revealed. It reveals that octametallic complex is an 'intermediate' in the formation of the tridecametallic species.

Research has been conducted on [NEt (sub)4] (sub)2 [Fe (sub)2 OCl (sub)6]. The authors describe the reaction of this compound with sodium benzoate, dimethyl-2-hydroxypyrimidine and 1,1,1-tris(hydroxymethyl)-ethane which leads to the undecametallic compound.

A new class of tetranuclear manganese single-molecule magnets with the pyridine-2,6-dimethanol monoanionic ligand pdmH(sub -) is reported. These complexes exhibit a frequency-dependent out-of-phase ac magnetic susceptibility signal.

A demonstration that a new pathway toward obtaining high-spin molecules with increased blocking temperatures could be provided by the deliberate use of bulky organic bridging ligands that could cause targeted structural distortions to the cores of polymetallic clusters is presented. The results reveal that the complex switches the dominant magnetic interactions among metal centers from antiferromagnetic to ferromagnetic resulting in an effective energy barrier.

A new [Mn(sub 18)](super 2+) single-molecule magnet (SMM) with a particularly large spin of S=13 is reported. Further it undergoes quantum tunneling of magnetization (QTM) and is both the largest spin and highest nuclearity SMM to exhibit this quantum behavior.

A study was conducted on two nanoscale oxide cages of [(Ni6COH)6{(NiCmhp)3}5 (Hmhp)(Cl)-(H2)2] (1) and [(Mn18)14(MeO)14(O2CCMe3)8(MeOH)6] (2) manifesting fragments of the rock salt structure and can synthesize very simple 1,3-binding ligands. X-ray analyses were performed on the nanoscale cages. The findings revealed antiferromagnetic exchange between the metal centers of 1 and 2. The results may be applied in understanding the process of nucleation.

A supracage assembly composed of four identical nickel (Ni4) cubanes and a central sodium (Na6) octahedron lying on a two-fold axis was designed. The six-coordinate cubes, which form two crystallographically equivalent pairs, contain mu3-OMe groups, mu3-O-atom and mu2-O-atom in the first two, third and fourth O-vertices, respectively. Phthalate groups, which act as bridges, interact with the central Na6 cage to facilitate their rectangular assembly.