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Studies on 3,5-di-tert-butylcatechol, aqueous ammonia and titanium, vanadium, germanium acid tin bis complexes of tridentate Schiff base biquinone ligand reveals the triplet ground states caused by intramolecular ferromagnetic interaction between two ligands. Specific radicals are required for ferromagnetic coupling between complexes. The complex is shown to be an admixture of vanadium and ligand orbitals.

The decanuclear iron (III) molecular ferric wheel complex, (Fe(OMe)2(O2CCH2Cl))10 results due to methanolysis of iron monochloroacetate and ferric nitrate. A previously unknown circular ring structure occurs due to geometry-induced convex and concave curvatures. The circular structure does not significantly affect the Mossbauer and geometric properties of the individual iron sites in the complex.

Analyses of two new hexanuclear ferric complexes, (Fe6(mu3-O)2(mu2-OH)2(mu2-O2CCH3)10(C7H11N2O)2).4CH2Cl2 and (Fe6(mu3-O)2(C6H6NO)8Cl4)(ClO4)2.4MeCN involved their preparation and a study of their X-ray structures and magnetochemical characteristics. The ground state spin varied from 0 to 5.

The magnetic characteristics of RE(hfac)3NITEt (RE = Tb, Er, Ho, hfac = hexafluoracetylacetonate, NITEt = 2-ethyl-4,4,5,5-tetramethyl-4, 5-dihydro-1H-imidazolyl-1-oxyl 3-oxide) are examined. Magnetic behavior of this compound is affected greatly by the presence of lanthanide ions with anisotropic ground states. Magnetic phase shifts to ordered states are evident.

Manganese(hexafluoroacetylacetonate) (Mn(hfac)2) and NITB combine to produce two dimensional, single crystals of (Mn(hfac)2)3-(NITBzald)2 having a layered molecular structure below 10 degrees kelvin. Nitronyl nitroxides are acted on by halogen groups forming two- or three-dimensional layered structures due to chain connection by the two NO radical groups and donor atoms. Tests revealed that increased structural complexity in the crystals do not lead to critical temperature increases. Critical temperatures may be increased by induction of stronger chain interactions by efficient exchange pathways.

The magnetic characteristics of molecular based materials containing rare erath ions and organic radicals were investigated. The results showed that materials with nonmagnetic rare earth ions behaved like one-dimensional antiferromagnets since superexchange reactions determined coupling between the radicals. In the case of isotropic gadolinium, the magnetic characteristics were dominated by next nearest neighbor interactions.

The magnetic properties of two polyoxovanadate anions, (V12As8O40(HCO2))3- and (V12As8O40(HCO2))5- were investigated. The results suggest that in the former compound there are six vanadium(IV) and six vanadium(V) ions, while in the latter there are eight vanadium(IV) and four vanadium(V) ions. The electron paramagnetic resonance spectra of the two compounds show opposite behaviors at low and high fields, probably due to field-dependent relaxation effects.

The syntheses of iron(III)-cathecolato complexes are discussed. These complexes have the general formulas (Fe(SS-CTH)(Cat))Y, (Fe(Cyclam)(Cat))Y, and (Fe(TACN)(Cat)-Cl), where SS-CTH = 5,5,6,12,12,14-hexamethyl-1,4,8, 11-tetraazacyclotetradecane; Cyclam = 1,4,8,11-tetraazacyclotetradecane; TACN = 1,4,7,-triazacyclononane; Cat = 3,5-di-tert-butylcatecholate; TCCat = tetrachlorocatecholatol Y = PF6, ClO4. Magnetic and spectral analyses show that the complexes are formulated as high-spin iron(III) derivatives. The electrochemical behavior of the complexes are also discussed.

A study was done on high-spin molecules of (Mn12O12(O2CR)16(H2o)4). It was shown that the solvated analogous complex formed from the manganese compound showed a ground state in zero applied fields and in large magnetic fields. On the other hand, the nonsolvated complex showed only a ground state in the zero field. Results from high-field EPR experiments with CO2 laser spectrometer reveal significant zero-field interactions for both complexes.

A study was done on the magnetic properties of K6(V15As6O42(H2O)). 8H2O(V15) and (NH4)6(V14As8O42(SO3))(V14) using variable-temperature magnetic susceptibility, EPR spectra and Huckel calculations. It was shown that the compound containing 15 vanadium ions has a unique multilayer structure whose magnetic properties were identified together with that of the coumpound having 14 vanadium ions. The magnetic properties of the high-nuclearity spin clusters can be elucidated using a perturbation and full matrix approach with spin hamiltonian formalism.

The reaction of Gd(hexafluoroacetylacetonate) (hfac)3.2H2O in n-heptane with 2-(2-pyridyl)- (NIToPy) and 2-(4-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro 1H-imidazolyl 3-oxide (NITpPy) results in the formation of Gd(hfac)3(NIToPy).0.5C7H16 and Gd(hfac)3(NITpPy), respectively. The X-ray analysis shows that the solid-state structure of the two complexes contain two Gd(III) and two nitronyl nitroxide radicals. The magnetic susceptibility measurements indicate that a ferromagnetic coupling exists between Gd(III) and both NIToPy and NITpPy.

The magnetic properties of several dinuclear complexes in which paramagnetic, 17-electron (MoNtris3,5-dimethylpyrazolyl)hydroborateCl fragments are linked by extended polypyridyl-type bridging ligands are determined. It is shown that the magnetic properties are related to various properties of the bridging ligand, including length, substitution pattern and conformation.

Fe8 high-spin molecules exhibit quantum spin tunneling at very low temperatures. Eight Fe3+ ions are sixfold coordinated and magnetically coupled through oxygen bridges. The net magnetization (MS=20 μB per molecule) results from competing antiferromagnetic interactions between the various Fe3+ ions (S=5/2). Because of the structural anisotropy of these molecules, the magnetization curve presents a hysteresis loop with staircases below 2 K. The staircases of the hysteresis loop are due to the quantum spin tunneling, which is temperature dependent for 400 mK3He-4He dilution refrigerator. This device, that takes advantage of the thermodynamic particularities of the 3He-4He mix, let us obtain x-ray magnetic circular dichroism (XMCD) spectra at 300 mK for this molecule. It has been possible to register an XMCD remnant signal, without magnetic field applied, at the iron L2,3 edges. XMCD coupled with ligand field multiplet calculations has allowed to determine the spin and orbit contributions to the magnetization of the Fe3+ ions. [ABSTRACT FROM AUTHOR]

Studies of two hexairon(III) clusters containing a mu6-oxo bridge reveal that the unusual bridging mode causes weak antiferromagnetic exchange-coupling interactions between the metal centers with J trans and J cis values of 19(2) and 9(1) per cm, respectively. The studies may be useful in the search for magneto-structural correlations in oxo-bridged polyiron aggregates.

The magnetic properties of K6(H3KV12As3O39 AsO4).8H2O were investigated to test the ability of valence bond summations to identify the localized and delocalized vanadium(IV) centers in polyoxovanadates. A model which accounts for the antiferromagnetic coupling constant J between the three localized vanadium(IV) ions and an effective coupling constant J' between the localized and delocalized vanadium(IV) centers was used. Parameters obtained from fitting the experimental thermal variation of (sub khi)T revealed that coupling constants depend greatly on the geometry of the complexes.

A mixed theoretical and experimental approach is used for determining the local magnetic anisotropy of the dysprosium(III) ion in a low-symmetry environment. The analysis of the temperature and field dependence of the magnetization has shown that the Dy ion has transmitted an antiferromagnetic interaction between radicals but that the Dy-radical interaction is ferromagnetic.

A study was conducted to determine the influence of electronic and structural variations induced by varying the N,N-bridge on the magnetic properties of Cu(II)-bis(oxamato) complexes. The spin population for the monomeric building blocks was found to be correlated to the exchange interaction of the corresponding trinuclear complexes on their geometry.

Single-crystal high-frequency electron paramagnetic resonance spectroscopy is used on an axial single molecule magnet in order to examine the origin of the transverse magnetic anisotropy. The results have shown the vital role played by the noncollinearity of the single-ion easy axes in the determination of high-order terms of the transverse magnetic.

The synthesis and characterization of various polyfinctional inorganic-organic hybrid materials are presented. The study also describes an unusual kind of nonlinear optical (NLO) active layered metal oxalates that have tunable magnetic properties and a very large second harmonic generation.

Tetrairon (III) single-molecule magnets (SMMs) with a propeller-like structure exhibit tuneable magnetic anistropy barriers in both heights and shape. The iron (III) ions exhibit a centered-triangular topology and are linked by six alkoxo bridges, which propagate antiferromagnetic interactions resulting in an S = 5 ground spin state.

The experimental magnetic data of the large transition-metal cluster [Mn19O12-MOE)14(MOEH)10].MOEH is fitted using a Monte Carlo (MC) simulation. The results confirm the suitability of MC techniques for the study of a high-nuclearity metal cluster without the need for high-performance workstations.

The synthesis, X-ray structure, magnetic properties, and DFT calculations of [{HC(CMeNAr)2}Mn]2 (Ar = 2,6-iPr2C6H3), the first complex with three-coordinate manganese(I) are reported. The magnetic investigations show a rare example of a high-spin manganese(I) complex with an antiferromagnetic interaction between the two Mn(I) centers.

Research has been conducted on compounds which contain Gd (super)3+, Sm (super)3+ and Yb (super)3+. The authors describe the synthesis, structure and magnetic properties of these compounds.

Research has been conducted on triply bridged bis-iminodioxolene dinuclear metal complexes. The authors report that these complexes have been synthesized via the use of bis-bidentate ligand and characterized by X-ray, HF-EPR and magnetic measurements.

This Microreview covers the preparation and investigation of Fe4 and Fe3M complexes with a propeller‐like structure, most of which function as single‐molecule magnets (SMMs). The magnetic characterization of these highly symmetric and chemically versatile complexes has enabled the establishment of important magneto‐structural correlations regarding magnetic anisotropy and magnetic relaxation mechanisms in SMM materials. Their chemical stability and easy functionalization have been further exploited to process them into thin films, down to monolayers and submonolayers, using solution or vapor‐phase methods. The proof so obtained that surface‐supported molecules can largely retain the rich magnetic behavior of bulk phases has been a turning point in SMM research, which has the integration of SMMs into spintronic devices among its most ambitious goals. Tetrairon(III) and related complexes with a propeller‐like structure not only served as excellent benchmark systems for studying single‐molecule magnet (SMM) behavior. They were also crucial to demonstrate that the memory effect of a SMM is not destroyed upon interaction with a metal surface, a result of primary importance in the emerging field of molecular quantum spintronics. [ABSTRACT FROM AUTHOR]

Single crystals of planar tetranuclear complex Fe4(OCH3)(sub 6)(dpm)(sub 6), which were earlier shown to have a typical single-molecule magnet behavior are studied using a high-frequency electron paramagnetic resonance (EPR) study. It is seen that as the temperature increases, the separation between the individual lines decreases and vanishes, which may be caused due to the contribution of fast relaxing excited states, whose population varies with temperature.

Some physical techniques used for the investigation of molecular magnetic clusters are studied. The use of high-field magnetization measurements, high -field -high frequency EPR spectroscopy, and neutron techniques like polarized neutron scattering and inelastic neutron scattering are reviewed.