Juan M. Manriquez

A Room-Temperature Molecular/Organic-Based Magnet

The reaction of bis(benzene)vanadium with tetracyanoethylene, TCNE, affords an insoluble amorphous black solid that exhibits field-dependent magnetization and hysteresis at room temperature. The critical temperature could not be estimated as it exceeds 350 kelvin, the thermal decomposition temperature of the sample. The empirical composition of the reported material is V(TCNE)x�Y(CH2Cl2) with x ∼ 2 and Y ∼ 1/2. On the basis of the available magnetic and infrared data, threedimensional antiferromagnetic exchange of the donor and acceptor spins resulting in ferrimagnetic behavior appears to be the mode of magnetic coupling.

Mössbauer spectroscopy study of new examples of highly delocalized, fully averaged mixed valence di-iron and iron-ruthenium compounds, [trans-μ-(pentalenyl)bis(pentamethylcyclopentadienyl iron]+BF4− and the related μ-symmetric-indacene system

We report that the (FeII, FeIII) versions of the title compounds as well as what is formally [Cp*FeII μ-pentalenyl RuIII Cp*]+BF4− (Cp* = η5-C5Me5) appear to be fully averaged mixed valence binuclear species on a Mössbauer spectroscopy time scale (∼100 ns) to as low as 1.5 K. This indicates essentially zero energy barrier to intramolecular electron transfer. At the other extreme, [Cp*FII μ-asymmetric-indacene FeIII Cp*]+BF4− exhibits trapped (discrete) FeII and FeIII valence states at ambient temperature.

57Fe Mossbauer Spectroscopy Studies of New Examples of Fully Averaged Mixed Valence Diiron and Iron/Ruthenium Compounds

Abstract We report that the Fe(II/III) compounds [(Cp*Fe)2L]·+ (L =pentalene and symmetric indacene) appear to be fully averaged mixed valent binuclear species on a Mossbauer spectroscopy time scale (∼100 ns) above 1.5K. This indicates essentially zero energy barrier to intramolecular electron transfer. In contrast, for L = asymmetric indacene trapped (discrete) Fe(II) and Fe(III) valence states are observed at ambient temperature. Finally the heterobinuclear complex [Cp*FeLCoCp*]n (L = pentalene) is similar to the homobinuclear Fe(II) analog for for n = 0, 1+ and similar to low spin FeIII) for the n = 2+ dication. The high degree of delocalization for the monocationic diiron and iron/ruthenium systems is attributed to the fused structure of the bridging ligands.

Magnetic Coupling Relationships for Bis(metallocene)-benzene Complexes

Abstract The synthesis and physical properties of meta- and para-bis(metallocene) benzene complexes with M = Fe, Co, Ni are reported. The electrochemical properties suggest greater electronic interaction between metal centers in the para-M complexes. In addition, the magnetic properties suggest different degrees of spin exchange for the meta and para complexes, with the latter exhibiting more pronounced antiferromagnetic coupling. These molecular complexes are considered prototypes for extended metallocene polymers.

A convenient synthesis of C5(CD3)5H. Synthesis and characterisation of Fe{η5-C5(CD3)5}2

The large scale synthesis of deuterio(pentamethylcyclopentadiene), C5(CD3)5H ([2H30]Cp*H), and subsequent synthesis of [2H30][Fe(η-Cp*)2] is described, together with i.r., Ramah, and solid state 2H n.m.r. spectroscopic characterisation.