Einsteinium compounds

Einsteinium compounds are compounds that contain the element einsteinium (Es). These compounds largely have einsteinium in the +3 oxidation state, or in some cases in the +2 and +4 oxidation states. Although einsteinium is relatively stable, with half-lives ranging from 20 days upwards, these compounds have not been studied in great detail.

Properties of einsteinium compounds

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Crystal structure and lattice constants of some Es compounds
Compound Color Symmetry Space group No Pearson symbol Lattice constants
(pm)
a b c
Es2O3 Colorless Cubic[1] Ia3 206 cI80 1076.6
Es2O3 Colorless Monoclinic[2] C2/m 12 mS30 1411 359 880
Es2O3 Colorless Hexagonal[2] P3m1 164 hP5 370 600
EsF3 Hexagonal[3]
EsF4 Monoclinic[4] C2/c 15 mS60
EsCl3 Orange Hexagonal[5][6] C63/m hP8 727 410
EsBr3 Yellow Monoclinic[7] C2/m 12 mS16 727 1259 681
EsI3 Amber Hexagonal[8][9] R3 148 hR24 753 2084
EsOCl Tetragonal[8][10] P4/nmm 394.8 670.2

Oxides

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Einsteinium(III) oxide (Es2O3) was obtained by burning einsteinium(III) nitrate. It forms colorless cubic crystals, which were first characterized from microgram samples sized about 30 nanometers.[11][1] Two other phases, monoclinic and hexagonal, are known for this oxide. The formation of a certain Es2O3 phase depends on the preparation technique and sample history, and there is no clear phase diagram. Interconversions between the three phases can occur spontaneously, as a result of self-irradiation or self-heating.[12] The hexagonal phase is isotypic with lanthanum oxide where the Es3+ ion is surrounded by a 6-coordinated group of O2− ions.[2][8]

Halides

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Einsteinium(III) iodide glowing in the dark

Einsteinium halides are known for the oxidation states +2 and +3.[10][13] The most stable state is +3 for all halides from fluoride to iodide.

Einsteinium(III) fluoride (EsF3) can be precipitated from einsteinium(III) chloride solutions upon reaction with fluoride ions. An alternative preparation procedure is to exposure einsteinium(III) oxide to chlorine trifluoride (ClF3) or F2 gas at a pressure of 1–2 atmospheres and a temperature between 300 and 400 °C. The EsF3 crystal structure is hexagonal, as in californium(III) fluoride (CfF3) where the Es3+ ions are 8-fold coordinated by fluorine ions in a bicapped trigonal prism arrangement.[3][14][15]

Einsteinium(III) chloride (EsCl3) can be prepared by annealing einsteinium(III) oxide in the atmosphere of dry hydrogen chloride vapors at about 500 °C for some 20 minutes. It crystallizes upon cooling at about 425 °C into an orange solid with a hexagonal structure of UCl3 type, where einsteinium atoms are 9-fold coordinated by chlorine atoms in a tricapped trigonal prism geometry.[6][14][16] Einsteinium(III) bromide (EsBr3) is a pale-yellow solid with a monoclinic structure of AlCl3 type, where the einsteinium atoms are octahedrally coordinated by bromine (coordination number 6).[9][14]

The divalent compounds of einsteinium are obtained by reducing the trivalent halides with hydrogen:[17]

2 EsX3 + H2 → 2 EsX2 + 2 HX,    X = F, Cl, Br, I

Einsteinium(II) chloride (EsCl2),[18] einsteinium(II) bromide (EsBr2),[19] and einsteinium(II) iodide (EsI2)[10] have been produced and characterized by optical absorption, with no structural information available yet.[9]

Known oxyhalides of einsteinium include EsOCl,[10] EsOBr[17] and EsOI.[10] These salts are synthesized by treating a trihalide with a vapor mixture of water and the corresponding hydrogen halide: for example, EsCl3 + H2O/HCl to obtain EsOCl.[20]

Organoeinsteinium compounds

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The high radioactivity of einsteinium has a potential use in radiation therapy, and organometallic complexes have been synthesized in order to deliver einsteinium atoms to an appropriate organ in the body. Experiments have been performed on injecting einsteinium citrate (as well as fermium compounds) to dogs.[21] Einsteinium(III) was also incorporated into beta-diketone chelate complexes, since analogous complexes with lanthanides previously showed strongest UV-excited luminescence among metallorganic compounds. When preparing einsteinium complexes, the Es3+ ions were 1000 times diluted with Gd3+ ions. This allowed reducing the radiation damage so that the compounds did not disintegrate during the period of 20 minutes required for the measurements. The resulting luminescence from Es3+ was much too weak to be detected. This was explained by the unfavorable relative energies of the individual constituents of the compound that hindered efficient energy transfer from the chelate matrix to Es3+ ions. Similar conclusion was drawn for other actinides americium, berkelium and fermium.[22]

Luminescence of Es3+ ions was however observed in inorganic hydrochloric acid solutions as well as in organic solution with di(2-ethylhexyl)orthophosphoric acid. It shows a broad peak at about 1064 nanometres (half-width about 100 nm) which can be resonantly excited by green light (ca. 495 nm wavelength). The luminescence has a lifetime of several microseconds and the quantum yield below 0.1%. The relatively high, compared to lanthanides, non-radiative decay rates in Es3+ were associated with the stronger interaction of f-electrons with the inner Es3+ electrons.[23]

See also

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References

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  1. ^ a b Haire, R. G.; Baybarz, R. D. (1973). "Identification and analysis of einsteinium sesquioxide by electron diffraction". Journal of Inorganic and Nuclear Chemistry. 35 (2): 489–496. doi:10.1016/0022-1902(73)80561-5.
  2. ^ a b c Haire, R. G. & Eyring, L. (1994). "Lanthanides and Actinides Chemistry". In K.A. Gscheidner, Jr.; et al. (eds.). Handbook on the Physics and Chemistry of Rare Earths. Vol. 18. North-Holland, New York. pp. 414–505. ISBN 978-0-444-81724-2.{{cite book}}: CS1 maint: location missing publisher (link)
  3. ^ a b Ensor, D. D.; Peterson, J. R.; Haire, R. G.; Young, J. P. (1981). "Absorption spectrophotometric study of 253EsF3 and its decay products in the bulk-phase solid state". Journal of Inorganic and Nuclear Chemistry. 43 (10): 2425–2427. doi:10.1016/0022-1902(81)80274-6.
  4. ^ Kleinschmidt, P. (1994). "Thermochemistry of the actinides". Journal of Alloys and Compounds. 213–214: 169–172. doi:10.1016/0925-8388(94)90898-2. Archived from the original on 2020-03-16. Retrieved 2019-07-14.
  5. ^ Fujita, D.; Cunningham, B. B.; Parsons, T. C. (1969). "Crystal structures and lattice parameters of einsteinium trichloride and einsteinium oxychloride". Inorganic and Nuclear Chemistry Letters. 5 (4): 307–313. doi:10.1016/0020-1650(69)80203-5. Archived from the original on 2020-03-13. Retrieved 2019-07-14.
  6. ^ a b Miasoedov, B. F. Analytical chemistry of transplutonium elements, Wiley, 1974 (Original from the University of California), ISBN 0-470-62715-8, p. 99
  7. ^ Fellows, R.; Peterson, J. R.; Noé, M.; Young, J. P.; Haire, R. G. (1975). "X-ray diffraction and spectroscopic studies of crystalline einsteinium(III) bromide, 253EsBr3". Inorganic and Nuclear Chemistry Letters. 11 (11): 737–742. doi:10.1016/0020-1650(75)80090-0.
  8. ^ a b c Haire, pp. 1595–1596
  9. ^ a b c Seaborg, p. 62
  10. ^ a b c d e Young, J. P.; Haire, R. G.; Peterson, J. R.; Ensor, D. D.; Fellow, R. L. (1981). "Chemical consequences of radioactive decay. 2. Spectrophotometric study of the ingrowth of berkelium-249 and californium-249 into halides of einsteinium-253". Inorganic Chemistry. 20 (11): 3979–3983. doi:10.1021/ic50225a076.
  11. ^ Greenwood, p. 1268
  12. ^ Haire, p. 1598
  13. ^ Holleman, p. 1969
  14. ^ a b c Greenwood, p. 1270
  15. ^ Young, J. P.; Haire, R. G.; Fellows, R. L.; Peterson, J. R. (1978). "Spectrophotometric studies of transcurium element halides and oxyhalides in the solid state". Journal of Radioanalytical Chemistry. 43 (2): 479–488. doi:10.1007/BF02519508. S2CID 95361392.
  16. ^ Fujita, D.; Cunningham, B. B.; Parsons, T. C.; Peterson, J. R. (1969). "The solution absorption spectrum of Es3+". Inorganic and Nuclear Chemistry Letters. 5 (4): 245–250. doi:10.1016/0020-1650(69)80192-3. Archived from the original on 2020-03-09. Retrieved 2019-07-14.
  17. ^ a b Peterson, J.R.; et al. (1979). "Preparation, characterization, and decay of einsteinium(II) in the solid state" (PDF). Le Journal de Physique. 40 (4): C4–111. CiteSeerX 10.1.1.729.8671. doi:10.1051/jphyscol:1979435. S2CID 95575017. Archived (PDF) from the original on 2012-03-07. Retrieved 2010-11-24. manuscript draft Archived 2013-05-13 at the Wayback Machine
  18. ^ Fellows, R.L.; Young, J.P.; Haire, R.G. and Peterson J.R. (1977) in: GJ McCarthy and JJ Rhyne (eds) The Rare Earths in Modern Science and Technology, Plenum Press, New York, pp. 493–499.
  19. ^ Young, J.P.; Haire R.G., Fellows, R.L.; Noe, M. and Peterson, J.R. (1976) "Spectroscopic and X-Ray Diffraction Studies of the Bromides of Californium-249 and Einsteinium-253", in: W. Müller and R. Lindner (eds.) Plutonium 1975, North Holland, Amsterdam, pp. 227–234.
  20. ^ Seaborg, p. 60
  21. ^ Haire, p. 1579
  22. ^ Nugent, Leonard J.; Burnett, J. L.; Baybarz, R. D.; Werner, George Knoll; Tanner, S. P.; Tarrant, J. R.; Keller, O. L. (1969). "Intramolecular energy transfer and sensitized luminescence in actinide(III) .beta.-diketone chelates". The Journal of Physical Chemistry. 73 (5): 1540–1549. doi:10.1021/j100725a060.
  23. ^ Beitz, J.; Wester, D.; Williams, C. (1983). "5f state interaction with inner coordination sphere ligands: Es3+ ion fluorescence in aqueous and organic phases". Journal of the Less Common Metals. 93 (2): 331–338. doi:10.1016/0022-5088(83)90178-9.
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