Thulium systems

Ordered magnetic systems with large 5.1.5. Thulium systems 68... 

Moseley s work not only shed much fight on the periodic system and the relationships between known elements and the radioactive isotopes, but was also a great stimulus in the search for the few elements remaining undiscovered (11). One of the first chemists to utilize the new method was Professor Georges Urbain of Paris, who took his rare earth preparations to Oxford for examination. Moseley showed him the characteristic fines of erbium, thulium, ytterbium, and lutetium, and confirmed in a few days the conclusions which Professor Urbain had made after twenty years... 

Johnson et al. (55) have reported a phonon-assisted energy exchange from trivalent erbium to trivalent thulium or to trivalent holmium. In this case, these authors were able to rule out resonance exchange completely Of some importance is that these systems are useful for laser oscillators, and the energy exchange results in a substantial decrease in threshold. 

Thulium(II) complexes are stabilized by phospholyl or arsolyl ligands that can be regarded as derived from the cyclopentadienyl group by replacing one CH group by a P or As atom. Their decreased n-donor capacity relative to the parent cyclopentadienyl system enhances the stability of the Tm(II) center, and stable complexes of the bent-sandwiched type have been isolated. 

The behaviour of lanthanum in dimethyl formamide (DMF) is quite different from that in methanol and acetonitrile. While perchlorate forms inner sphere complexes with lanthanides in acetonitrile [31], no such complexes are formed in DMF [32]. The coordination properties in DMF solutions were studied by NMR and UV-Vis spectroscopy techniques [33,34], The rate of DMF exchange in the system ytterbium perchlorate-DMF-CD2CI2 was slow enough that 1H NMR resonances permitted the determination of the mean coordination number to be 7.8 0.2. Similar determination in the case of thulium(III) gave a mean coordination number of 7.7 0.2. Thus it was concluded that the predominant species in heavy lanthanides is Ln(DMF)g+ in DMF solutions. In the case of lighter lanthanides, the following equilibrium exists... 

In the thulium + chlorine system a number of such homologues is believed to exist in the region TmQ2+a. Thermal analysis suggests the existence of at least nine compounds in the range 0.04q = f5 < O.II2, i.e. Tm Q2n+i with 25.0 > 8.9. In this case... 

Little information about the health effects of thulium is available. Evidence suggests that it may be a mild irritant to the skin, eyes, and respiratory system. It is probably not very toxic if ingested. People who work with the metal are advised to use good safety practices to avoid coming into contact with the metal any more than necessary. 

The phase diagram of the system thulium-selenium has been studied by Fritzler, Kaldis, and Jilek [82FR1/KAL]. 

The effect of other Ln(OTf)3 was also examined. As shown in table 31, the choice of lanthanide element strongly influenced the yields and selectivities. A slight difference between the two catalyst systems (catalysts A and B) on the effect of the lanthanide elements was also observed. In catalyst A, lutetium triflate (Lu(OTf)3) was also effective in generating the endo Diels-Alder adduct in 93% ee. The yields and selectivities diminished rapidly in accordance with the enlargement of the ionic radii. In catalyst B, on the other hand, the best results were obtained when thulium triflate (Tm(OTf)3) or erbium triflate (Er(OTf)3) was employed. Deviations to either larger or smaller ionic... 

The low-valent molecular chemistry of rare earths was once thought to be restricted to divalent samarium, europium and ytterbium. This chemistry has now been extended to many of the rare earths in the zero-valent state, to mono- and divalent scandium, to divalent lanthanum, cerium, neodymium, dysprosium and thulium, and to systems in which dinitrogen is activated and that may contain yet other highly reactive divalent rare earths. It is the opinion of the author that this research area is likely to find fascinating developments in the near future. 

Thulium is one of the most expensive of the rare earths, and therefore has little applications (Emsley 2001). Thulium is used as a dopant in YAG and YLF. Efficient flash lamp and laser diode-pumped laser operation has been achieved in Tm " YAG and Tm " YLF co-doped either with Cr " or Ho ". Thulium is also used in thulium-doped holmium lasers, which have outputs in the 2 pm region, a wavelength range of interest for coherent radar systems, remote sensing and medical applications (Koechner 2006). 

---