Terpyridine

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Terpyridine
Terpyridine.svg
Identifiers
CAS number 1148-79-4 YesY
PubChem 70848
ChemSpider 64012 YesY
ChEBI CHEBI:245199 YesY
ChEMBL CHEMBL89445 YesY
Jmol-3D images Image 1
Properties
Molecular formula C15H11N3
Molar mass 233.27 g mol−1
Appearance colourless solid
Melting point 88 °C
Boiling point 370 °C[1]
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Terpyridine (2,2';6',2"-terpyridine, often abbreviated to terpy or tpy) is a heterocyclic compound derived from pyridine. This colourless solid is used as a ligand in coordination chemistry.

Synthesis[edit]

Terpyridine was first synthesized by G. Morgan and F. H. Burstall in 1932 by the oxidative coupling of pyridines. This method, however, proceeded in low yields. In 1991, a more efficient synthesis was described that involves the condensation of 2-acetylpyridine and enaminone, which is prepared by the reaction of 2-acetylpyridine with N,N-dimethylformamide dimethyl acetal. Alternatively, the base-catalyzed reaction of 2-acetylpyridine with carbon disulfide followed by alkylation with methyl iodide gives C5H4NCOCH=C(SMe)2. Condensation of this species with 2-acetylpyridine forms the related 1,5-diketone, which condenses with ammonium acetate to form a terpyridine. Treatment of this derivative with Raney nickel remove the thioether group.[2]

Other methods have been developed for the synthesis of terpyridine and its substituted derivatives. Substituted terpyridines are also synthesized from palladium-catalyzed cross-coupling reactions. It can be prepared from bis-triazinyl pyridine.

Properties[edit]

Terpyridine is a tridentate ligand that binds metals at three meridional sites giving two adjacent 5-membered MN2C2 chelate rings.[3] Terpyridine forms complexes with most transition metal ion as do other polypyridine compounds, such as 2,2'-bipyridine and 1,10-phenanthroline. Complexes containing two terpyridine complexes, i.e. [M(terpy)2]n+ are common. They differ structurally from the related [M(bipy)3]n+ complexes in being achiral.

Terpyridine complexes, like other polypyridine complexes, exhibit characteristic optical and electrochemical properties: metal-to-ligand charge transfer (MLCT) in the visible region, reversible reduction and oxidation, and fairly intense luminescence.

Because they are pi-acceptors, terpyridine and bipyridine tend to stabilize metals in lower oxidation states. For instance in acetonitrile solution, it is possible to generate the [M(terpyridine)2]+ (M = Ni, Co).

Related compounds[edit]

The bis-triazinyl pyridines are topologically related to terpyridine in their binding to metals.

See also[edit]

References[edit]

  1. ^ Lide, D. R. (1998), Handbook of Chemistry and Physics (87 ed.), Boca Raton, FL: CRC Press, pp. 3–510, ISBN 0-8493-0594-2 
  2. ^ Potts, K. T.; Ralli, P.; Theodoridis, G.; Winslow, P. (1990), "2,2':6',2' - Terpyridine", Org. Synth. ; Coll. Vol. 7: 476 
  3. ^ Gavrilova, A. L.; Bosnich, B. (2004). "Principles of Mononucleating and Binucleating Ligand Design". Chemical Reviews 104 (2): 349–383. doi:10.1021/cr020604g.