Paramagnetic complex ordering

Development of EPR Method for Examination of Paramagnetic Complex Ordering in Films... 

The possibility of coordinating functionalized TTFs onto polynuclear core is a very stimulating issue because it is now well established that polynuclear cores, with some restrictions of course, can act as SMMs. We started a systematic investigation of polynuclear paramagnetic complexes with TTF CH=CH—py ligands to scan the possibility to access to bifunctional molecules which can act at the same time as SMM and single component metal. We succeeded in coordinating our modified TTFs to several homo- or heteropolynuclear complexes. This opens new perspectives in the field of multifunctional materials. The size of these molecules, which is of the order of 4 nm, is another important aspect in the field of molecular scale electronic. 

Extensive electrochemical studies of complexes of Type I were also reported (164-166). It was ascertained that [Rh2]2+ di-isocyanide complexes are more susceptible to oxidation than their dicarbonyl analogues, and that one-electron oxidations of the di-isocyanide complexes produce stable and isolable paramagnetic [Rh2]3+ species (165). In particular, paramagnetic complexes of the type [Rh2(/i-EE )2(f-BuNC)2(p-pz )](PF6)2 (EE = dppm, dapm, or dpam Hpz = Hpz, 4-MepzH, Hdmpz, 4-BrdmpzH, or 3,4,5-BrpzH) containing the [Rh2]3 + core were obtained via controlled potential electrolysis of the parent [Rh2]2+ species [Rh20i-EE )2(f-BuNC)2(/ -pz )](PF6). The X-ray crystal structure of [Rh2(/j.-dppm)2(r-BuNC)2(/x-dmpz)](PF6)2 showed a Rh- -Rh distance of about 2.83 A, which is consistent with a bonding order of 0.5 for the [Rh2]3 + core (166). 

The NMR spectra of paramagnetic complexes are very different from those of the diamagnetic compounds that have been discussed up to this point. For example, complexation shifts in systems containing unpaired electrons are often an order of magnitude larger than those observed in diamagnetic complexes. As a result, a new theoretical treatment must be given for these... 

Similarity with cobalt is also apparent in the affinity of Rh and iH for ammonia and amines. The kinetic inertness of the ammines of Rh has led to the use of several of them in studies of the trans effect (p. 1163) in octahedral complexes, while the ammines of Ir are so stable as to withstand boiling in aqueous alkali. Stable complexes such as [M(C204)3], [M(acac)3] and [M(CN)5] are formed by all three metals. Force constants obtained from the infrared spectra of the hexacyano complexes indicate that the M--C bond strength increases in the order Co < Rh < [r. Like cobalt, rhodium too forms bridged superoxides such as the blue, paramagnetic, fCl(py)4Rh-02-Rh(py)4Cll produced by aerial oxidation of aqueous ethanolic solutions of RhCL and pyridine.In fact it seems likely that many of the species produced by oxidation of aqueous solutions of Rh and presumed to contain the metal in higher oxidation states, are actually superoxides of Rh . ... 

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