8-Hydroxyquinoline

8-Hydroxyquinoline

8-Hydroxyquinoline

Chemical compound

8-Hydroxyquinoline (also known as oxine) is an organic compound derived from the heterocycle quinoline. A colorless solid, its conjugate base is a chelating agent, which is used for the quantitative determination of metal ions.

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In aqueous solution 8-hydroxyquinoline has a pKa value of ca. 9.9[1] It reacts with metal ions, losing the proton and forming 8-hydroxyquinolinato-chelate complexes.

Tris(8-hydroxyquinolinato)aluminium[2]

The aluminium complex,[3] is a common component of organic light-emitting diodes (OLEDs). Substituents on the quinoline ring affect the luminescence properties.[4]

In its photo-induced excited-state, 8-hydroxyquinoline converts to zwitterionic isomers, in which the hydrogen atom is transferred from oxygen to nitrogen.[5]

Bioactivity

The complexes as well as the heterocycle itself exhibit antiseptic, disinfectant, and pesticide properties,[6][7] functioning as a transcription inhibitor.[8] Its solution in alcohol is used in liquid bandages. It once was of interest as an anti-cancer drug.[9]

A thiol analogue, 8-mercaptoquinoline is also known.[10]

The roots of the invasive plant Centaurea diffusa release 8-hydroxyquinoline, which has a negative effect on plants that have not co-evolved with it.[11]

See also

References

  1. [1]
    Albert, A.; Phillips, J. N. (1956). "264. Ionization Constants of Heterocyclic Substances. Part II. Hydroxy-Derivatives of Nitrogenous Six-Membered Ring-Compounds". Journal of the Chemical Society (Resumed). 1956: 1294–1304. doi:10.1039/JR9560001294.
  2. [2]
    Cölle, M.; Dinnebier, R. E.; Brütting, W. (2002). "The structure of the blue luminescent δ-phase of tris(8-hydroxyquinoline)aluminium(III) (Alq3)". Chemical Communications. 2002 (23): 2908–9. doi:10.1039/b209164j. PMID 12478807. S2CID 96135270.
  3. [3]
    Katakura, R.; Koide, Y. (2006). "Configuration-Specific Synthesis of the Facial and Meridional Isomers of Tris(8-hydroxyquinolinate)aluminum (Alq3)". Inorganic Chemistry. 45 (15): 5730–5732. doi:10.1021/ic060594s. PMID 16841973.
  4. [4]
    Montes, V. A.; Pohl, R.; Shinar, J.; Anzenbacher, P. Jr. (2006). "Effective Manipulation of the Electronic Effects and Its Influence on the Emission of 5-Substituted Tris(8-quinolinolate) Aluminum(III) Complexes". Chemistry: A European Journal. 12 (17): 4523–4535. doi:10.1002/chem.200501403. PMID 16619313.
  5. [5]
    Bardez, E.; Devol, I.; Larrey, B.; Valeur, B. (1997). "Excited-State Processes in 8-Hydroxyquinoline: Photoinduced Tautomerization and Solvation Effects". The Journal of Physical Chemistry B. 101 (39): 7786–7793. doi:10.1021/jp971293u.
  6. [6]
    Phillips, J. P. (1956). "The Reactions of 8-Quinolinol". Chemical Reviews. 56 (2): 271–297. doi:10.1021/cr50008a003.
  7. [7]
    "8-Hydroxyquinoline". Medical Dictionary Online. Archived from the original on 2016-10-09. Retrieved 2016-03-09.
  8. [8]
    "8-Hydroxyquinoline". Sigma-Aldrich. Retrieved 2022-02-15.
  9. [9]
    Shen, A. Y.; Wu, S. N.; Chiu, C. T. (1999). "Synthesis and Cytotoxicity Evaluation of some 8-Hydroxyquinoline Derivatives". Journal of Pharmacy and Pharmacology. 51 (5): 543–548. doi:10.1211/0022357991772826. PMID 10411213. S2CID 33085238.
  10. [10]
    Fleischer, H. (2005). "Structural Chemistry of Complexes of (n-1)d10ns Metal Ions with β-N-Donor Substituted Thiolate Ligands (m=0, 2)". Coordination Chemistry Reviews. 249 (7–8): 799–827. doi:10.1016/j.ccr.2004.08.024.
  11. [11]
    Vivanco, J.M.; Bais, H.P.; Stermitz, F.R.; Thelen, G.C.; Callaway, R.M. (2004). "Biogeographical variation in community response to root allelochemistry: novel weapons and exotic invasion". Ecology Letters. 7 (4): 285–292. Bibcode:2004EcolL...7..285V. doi:10.1111/j.1461-0248.2004.00576.x.
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