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The syntheses and characterization of the iron(II) complexes of the pentadentate amide-containing macrocyclic ligand 3,6,9,12,18-pentaazabicyclo-[12,3,1]octadeca-1(18),14,16-triene-2,13-dione ([H.sub.2]pydione[N.sub.5]) are reported. The complexes maintain a high-spin state even at low temperature and detailed kinetic studies of oxygenation of the iron(II) complexes showed that the deprotonation state of the complex has a profound effect on the reactivity with dioxygen.

Diruthenium tetraacetate monocations are utilized as building blocks for cubic 3-D network structured molecule-based magnets. The ruthenium dimer monocations can be utilized as building blocks for molecule-based magnets.

A new stable iron(III) complex with a pentadentate amide containing ligand H(sub 2)pydioneN(sub 5) was prepared and fully characterized. The set of donor atoms provided by H(sub 2)pydioneN(sub 5) contains one pyridine nitrogen, two nitrogen atoms from deprotonated amide groups, and two secondary amines and is similar to that of blemoycin and many of previously synthesized bleomycin models.

Research has been conducted on Mn(II) systems, a similar magnetically coupled Fe(III) (sub)9 complex and Zn(II) (sub)9, (Pb(II) (sub)3) (sub)2 and Fe(III) (sub)5 derivatives with the ligands. The structures, magnetic properties amd Mossbauer data of these structures are reported.

Research has been conducted on the single-molecule magnet salts. The preparation of these salts has been carried out in investigating the effects of paramagnetic cations on the anionic single-molecule magnets' relaxation behavior and the results are reported.

Research has been conducted on the one-to-one charge-transfer salt. The synthesis and single-crystal structure of this salt are described.

Alpha- and beta-Fe(OETAP) have been identified as the two polymorphs of iron(II) octaethyltetraazaporphyrin at room temperature. SQUID magnetometry was used to confirm that the alpha phase of iron(II) octaethyltetraporphyrin is a canted molecular ferromagnet. Beta-Fe(OETAP), on the other hand, was found to exhibit comparable room-temperature magnetic properties. The two polymorphs can be differentiated by their cooperative interactions. The beta phase has interactions that are almost completely quenched and appear to have no ordering.

Several alkyl complexes of molybdenum containing the ((Mesub3SiNCHsub2CHsub2)sub3N)super3- ligand, have been synthsized and characterized and studied for decomposition. Dehydrogenation of (Nsub3N)-MoChsub2R' complexes yielded (Nsub3N)Mo=CR' complexes, and cleavage of C-C bonds in cyclopropyl and cyclobutyl complexes, yielded alkylidyne complexes.

Electrochemical, spectroscopic, and X-ray crystallographic studies of organometallic compounds such as (Cp*M(ligand)M'Cp*)n (M, M' = Fe, Co, Ni; n = O, 1+, 2+; ligand = pentalene, indacene), indicate that delocalized strong electron coupling exists between metal sites. The oxidation state does not significantly change the molecular structure of the organometallic compounds and the Cp*M moieties occupy the opposite faces of the fused nu-bridging ring systems.

The compound tetramethylpiperazinium pentachloroferrate(III), C8H20Cl5N2Fe, crystallizes in the monoclinic space group C2/c, and a five-coordinate trigonal bipyramidal (FeCl5)2- species is present in an ionic crystal lattice, as reflected by the single-crystal X-ray diffraction study. A three-dimensional antiferromagnetic ground state in a long range magnetic order between 6 and 7 Kelvin is observed by Fe(super 59) Mossbauer spectroscopy and a.c. susceptometry.

Studies of the Cp(super *)Fe(mu-C14H18-Si2)FeCp(super *) reveal that electrochemical oxidation of the complex in CH2Cl2 occurs through two reversible oxidations 0.268 V apart. The reaction of the compound with TCNE results in the formation of ((Cp*. Fe)2(mu-C14H18Si2)+)(TCNE.-). This compound appears to be completely valence-trapped on the Mossbauer time scale.

A diiron(II) complex is synthesized with a novel aqua-hydroxo bridging motif, a member of the diiron diamond core family. Observations suggest that the complex is stable in solution in nonpolar solvent as well as in the solid state, while two hydroxides are not required to keep the diiron core intact.

The thermal hysteresis of the magnetic susceptibility of the molecule-based solid [Co (super III) Cp2](super +)[Fe(super III)I4](super -) is reported. Bistable materials have great potential in next-generation sensor, switching, and actuator devices.

The monomeric iron(II) amido derivatives are prepared and analyzed in order to determine the effects of geometric changes on their unusual magnetic properties. The data for the two amido complexes have shown a very large quenching of the orbital magnetic moment upon bending the linear geometry and also a strong correlation of high internal orbital field component ([H.sub.L]) with overall formal symmetry.

A usual two-coordinate iron(II) amide, the di(tert-butyl)amide complex that retains a linear N-Fe-N framework is described. The studies have shown that the extraordinary orbital magnetic effects can arise in linear transition metal complexes in which orbital degeneracies are not broken by Jahn-Teller or Renner-Teller distortions.

The synthesis, spectroscopic and physical properties of Cr[M[CN.sub.6]] (M = V, Cr, Mn, Fe) Prussian blue analogues synthesized from [[Cr.sup.III][NCMe.sup.6].sup.3+] is discussed. Findings reveal strong antiferromagnetic coupling for M = V, Cr and Mn.

The significant effects of the absence of Jahn-Teller distortion on the magnetism of a linear coordination compound of high-spin iron(II) are reported. These were studied in the contexts of its low temperature Mossbauer spectrum and dc magnetization.

The title compound has a structure involving 2D extended double-layer sheets of alternating tetrahedral and octahedral iron (II) ions singly bridged by imidazolate ligands. Structural phase transitions at 151 and ~ 135 K are studied by variable-temperature ac and dc susceptibility, X-ray crystallography, and Mossbauer spectroscopy techniques.

The magnetic susceptibility of a powdered sample of [Cr (NH3)6][FeCl6] has been measured in the temperature range 1.85 to 110 K in applied magnetic fields of 100 and 10 000 Oe. A magnetic phase transition near 2.8 K is apparent in the low field data set. The transition is confirmed by zero field Mössbauer spectroscopy data. The magnetic data above the phase transition may be fit to the Néel hyperbola for a ferrimagnet: χ-1=(T-θ)/C-ζ/(T-θ’) with best-fit values of C=6.58 emu K, θ=-14.1 K, θ’=2.22 K, and ζ=10.1 emu K. Assuming a structure similar to [Co(NH3)6] [FeCl6] and mean field theory, the intrasublattice coupling constants are 0.12 cm-1, and the intersublattice coupling constant, Jab, is -0.21 cm-1. The value of Jab is confirmed by a change in slope of the magnetization data near 2000 Oe. [ABSTRACT FROM AUTHOR]

Multiple HFEPR transitions for HS Fe(ll) with high S/N ratio are observed, in the case for a cis-FeN2N4 chromophore complex, bis(2,2-bi-2-thiazoline)-bis(isothiocyanato)iron(ll), according to demonstration. Mossbauer and magnetic susceptibility studies corroborated that HFEPR can detect strong, well-defined resonances of HS Fe(ll) in a pseudo-octahedral complex characterized by a large, positive D.

Molecular/Organic Ferromagnets MAGNETS HAVE FASCINATED MAN SINCE THE OBSERVATION that iron is attracted to lodestone. Early in history the Chinese took advantage of this observation and invented the compass. Today [...]