Compounds magnetic behavior

Rhenium(VI) complexes, 4,194 alkoxides, 4,196 amides, 4,194 amines, 4,199 carboxylates, 4,199 dimethylformamide, 4,199 dioxane, 4,198 halides, 4,195,199 2-hydroxypyridine, 4,199 imides, 4,194 magnetic behavior, 1,271 mixed sulfur-nitrogen compounds, 4,196 N heterocycles, 4,199 nitrides, 4,194 oxide halides, 4, 195 oxoanions,4,196 pyridine, 4,199 sulfates, 4,198 sulfur compounds, 4,196 tellurates, 4,198... 

The interplay between magnetic coupling and ST in 2,2 -bipyrimidine (bpym)-bridged iron(ll) dinuclear compounds has been studied by magnetic susceptibility and Fe Mossbauer spectroscopy [24]. The molecular stmctures of [Fe(bpym) (NCS)2]2(bpym) and [[Fe(bt)(NCS)2]2(bpym) (bt = 2,2 -bithiazoline) are shown in Fig. 8.12. The magnetic behavior in the form of XmT versus Tplots, being the... 

This magnetic behavior is very sensitive to the chemical structure of the spin carrier and to the crystal packing. For instance, for the para-nitro substituted derivative, Nit(p-NO )Ph, which crystallizes in four different phases, the p phase only orders ferromagnetically (Tc = 0.6 K) [8,9], Moreover, attaching the nitro group in the meta-, rather than the / ara-position of the phenyl, leads to an antiferromagnetic compound [2],... 

The structurally related salts [M(Cp )2] [M (tds)2] (M = Fe, Mn, Cr M = Ni, Pt) and [Fe(Cp )2][Pt(tds)2] allowed a systematic study of the effect of a diversity of variables on the magnetic behavior of these compounds, such as the variation of the spin of the cation, the role of the single ion anisotropy, the effect of the variation of the size of atoms involved in the intermolecular contacts. Furthermore, the analysis of the intermolecular contacts in these compounds provided a reasonable interpretation of the intra and interchain magnetic coupling, and its relative strength within the series [44, 45]. 

The magnetic behavior of [Fe(C5Me4SCMe3)2][M(mnt)2] (M = Ni, Pt) is dominated by FM interactions (6 — 3 K, M = Ni and Pt), which can be attributed to the D+A intrachain interactions. The weaker interchain interactions are expected to be AF. As in the previous compounds exhibiting this type of structure a metamagnetic behavior is also expected to occur at low temperatures. 

In [Co(Cp )2][Ni(dmit)2], where the [Co(Cp )2]+ cations are diamagnetic (S — 0), the paramagnetic susceptibility arises only from the contribution of the anionic network, where S — 1/2 for [Ni(dmit)2]. The magnetic behavior of this compound is dominated by weak FM interactions (6 — 0.5 K) [54]. The observed dominance of the FM interactions in this compound confirms that the FM interactions between the i(dmit>2 units in the dimers are stronger than the AF A A intrachain interactions. 

In the case of [Fe(Cp )2][Pd(dmit)2], two polymorphs were obtained, but the structure was only determined for the a phase, which is distinct from the above-mentioned compounds and will be described further down. In spite of the fact that the crystal structure of the (3-[Fe(Cp )2][Pd(dmit)2] could not be determined, this compound shows a magnetic behavior that resembles that observed for [M(Cp )2] [Ni(dmit)2], with M = Fe and Mn, exhibiting a f) value of 2.6 K [51]. Furthermore, the isothermal obtained at 2 K closely follows that exhibited by [Ni(Cp )2][Ni (dmit)2]. This strongly suggests that (3-[Fe(Cp )2][Pd(dmit)2] presents a similar structure as those compounds. 

The complexity of the crystal structure of the [M(Cp )2][M (bdt)2] salts and the large number of intermolecular contacts in this series of complexes prevents a clear interpretation of the magnetic behavior and a correlation between the crystal structures and the magnetic properties. However, the saturation magnetization value in the case of the compounds [Mn(Cp )2][M (bdt)2] (M = Ni and Pt) is consistent with a D+A- AF coupling. A similar coupling is expected to occur in [Fe(Cp )2][M (bdt)2] (M = Ni and Pt), where %T shows a similar behavior, typical of a FIM above the ordering temperature. 

Most of the salts based on decamethylmetallocenium radical cations and on planar metal bisdichalcogenate radical anions reported so far present crystal structures with mixed linear chain basic motives. The only known exception is [Fe(Cp )2][Ni (mnt)2], which exhibits another type of crystal structure based on a D+ [A2]2 D+ repeat unit [28]. In the case of this compound the magnetic behavior is dominated by the intradimer antiferromagnetic interactions. 

In the salts based on segregated stacks of metallocenium-based cations with [M(mnt)2)] (M = Ni, Pd and Pt) anions, the anionic stacks are isolated from each other by the cations in a few compounds these stacks are regular (at high temperatures) but in most cases the [M(mnt)2)] units form dimers. The magnetic behavior of these compounds is dominated by the AF interactions between the anion units. 

Magnetic Susceptibility. Compounds 105 and 105a provide rare examples of porphyrinic macrocyles with central Mn(III) ions that are truly isolated from nearest-neighbor interactions. This phenomena simplifies the interpretation of the magnetic behavior of these compounds [high-spin Mn(III) d4, S = 2,... 

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