Chemical compound

Titanium(II) oxide (TiO) is an inorganic chemical compound of titanium and oxygen. It can be prepared from titanium dioxide and titanium metal at 1500 °C.[1] It is non-stoichiometric in a range TiO0.7 to TiO1.3 and this is caused by vacancies of either Ti or O in the defect rock salt structure.[1] In pure TiO 15% of both Ti and O sites are vacant.[1] Careful annealing can cause ordering of the vacancies producing a monoclinic form which has 5 TiO units in the primitive cell that exhibits lower resistivity.[2] A high temperature form with titanium atoms with trigonal prismatic coordination is also known.[3] Acid solutions of TiO are stable for a short time then decompose to give hydrogen:[1]

2 Ti2+(aq) + 2 H+(aq) → 2 Ti3+(aq) + H2(g)

Gas-phase TiO shows strong bands in the optical spectra of cool (M-type) stars.[4][5] In 2017, TiO was claimed to be detected in an exoplanet atmosphere for the first time; a result which is still debated in the literature.[6][7] Additionally, evidence has been obtained for the presence of the diatomic molecule TiO in the interstellar medium.[8]

References

  1. ^ a b c d Holleman, Arnold Frederik; Wiberg, Egon (2001), Wiberg, Nils (ed.), Inorganic Chemistry, translated by Eagleson, Mary; Brewer, William, San Diego/Berlin: Academic Press/De Gruyter, ISBN 0-12-352651-5
  2. ^ Banus, M. D.; Reed, T. B.; Strauss, A. J. (1972-04-15). "Electrical and Magnetic Properties of TiO and VO". Physical Review B. American Physical Society (APS). 5 (8): 2775–2784. Bibcode:1972PhRvB...5.2775B. doi:10.1103/physrevb.5.2775. ISSN 0556-2805.
  3. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  4. ^ Jorgensen, Uffe G. (April 1994). "Effects of TiO in stellar atmospheres". Astronomy and Astrophysics. 284 (1): 179–186. Bibcode:1994A&A...284..179J.
  5. ^ "Spectral classification of late-type dwarfs".
  6. ^ Sedaghati, Elyar; Boffin, Henri M.J.; MacDonald, Ryan J.; Gandhi, Siddharth; Madhusudhan, Nikku; Gibson, Neale P.; Oshagh, Mahmoudreza; Claret, Antonio; Rauer, Heike (14 September 2017). "Detection of titanium oxide in the atmosphere of a hot Jupiter". Nature. 549 (7671): 238–241. arXiv:1709.04118. Bibcode:2017Natur.549..238S. doi:10.1038/nature23651. PMID 28905896. S2CID 205259502.
  7. ^ Espinoza, Nestor; et al. (January 2019). "ACCESS: A featureless optical transmission spectrum for WASP-19b from Magellan/IMACS". MNRAS. 482 (2): 2065–2087. arXiv:1807.10652. Bibcode:2019MNRAS.482.2065E. doi:10.1093/mnras/sty2691.
  8. ^ Dyck, H. M.; Nordgren, Tyler E. (2002). "The Effect of TiO Absorption on Optical and Infrared Angular Diameters of Cool Stars". The Astronomical Journal. American Astronomical Society. 124 (1): 541–545. Bibcode:2002AJ....124..541D. doi:10.1086/341039. ISSN 0004-6256.