View source for Terpyridine

{{Chembox
| Watchedfields = changed
| verifiedrevid = 306220274
| ImageFile = Terpyridine.svg
| ImageSize = 
| IUPACName = 2,6-bis(2-pyridyl)pyridine
| OtherNames = tripyridyl
| Section1 = {{Chembox Identifiers
|  CASNo_Ref = {{cascite}}
| CASNo = 1148-79-4
|  PubChem = 70848
|  ChemSpiderID = 64012
|  SMILES = c1ccnc(c1)c2cccc(n2)c3ccccn3
|  InChI = InChI=1S/C15H11N3/c1-3-10-16-12(6-1)14-8-5-9-15(18-14)13-7-2-4-11-17-13/h1-11H
  }}
| Section2 = {{Chembox Properties
|  C=15 | H=11 | N=3
|  Appearance = colourless solid
|  Density = 
|  MeltingPt = 88 °C
|  BoilingPt = 370 °C<ref name="hand">
{{Citation
 | last = Lide
 | first = David R.
 | author-link = 
 | last2 = 
 | first2 = 
 | author2-link =
 | publication-date =
 | date =
 | year = 1998
 | title = Handbook of Chemistry and Physics
 | edition = 87
 | volume = 
 | series =
 | publication-place = Boca Raton, FL
 | place = 
 | publisher = CRC Press
 | id =
 | isbn = 0849305942
 | doi =
 | oclc =
 | pages = 3–510
 | url = 
 | accessdate =
}}</ref>
|  Solubility =
  }}
| Section3 = {{Chembox Hazards
|  MainHazards = 
|  FlashPt = 
|  Autoignition =
  }}
}}
'''Terpyridine''' (2,2';6',2"-terpyridine) is a [[heterocyclic compound]] derived from [[pyridine]]. This colourless solid is used as a ligand in [[coordination chemistry]].

==Synthesis==
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 C<sub>5</sub>H<sub>4</sub>NCOCH=C(SMe)<sub>2</sub>.  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.<ref>{{OrgSynth | author = Potts, K. T.; Ralli, P.; Theodoridis, G.; Winslow, P. | title = 2,2':6',2' -Terpyridine | collvol = 7 | collvolpages = 476 | year = 1990 | prep = cv7p0476}}</ref>

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

==Properties==
Terpyridine is a tridentate [[ligand]] that binds metals at three meridional sites giving two adjacent 5-membered MN<sub>2</sub>C<sub>2</sub> chelate rings.<ref>Anna L. Gavrilova, Brice Bosnich "Principles of Mononucleating and Binucleating Ligand Design" Chem. Rev. 2004, 104, 349-383. {{DOI|10.1021/cr020604g}}</ref> Terpy forms complexes with most [[transition metal]] [[ion]] as do other [[polypyridine complex|polypyridine compounds]], such as [[2,2'-bipyridine]] and 1,10-phenanthroline. Complexes containing two terpyridine complexes, i.e. [M(terpy)<sub>2</sub>]<sup>n+</sup> are common.  They differ structurally from the related [M(bipy)<sub>3</sub>]<sup>n+</sup> 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 [[Redox|reduction]] and [[oxidation]], and fairly intense [[luminescence]].

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

==Related compounds==
The [[bis-triazinyl pyridines]] are topologically related to terpy in their binding to metals.

==See also==
* [[Pincer ligand]]
* [[Chelating ligand]]

==References==
{{reflist}}

[[Category:Chelating agents]]
[[Category:Pyridines]]

[[de:Terpyridin]]
[[Category:2Fix]]