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style="background: #F8EABA; text-align: center;" colspan="2" | Identifiers
CAS number 66-71-7 YesY
RTECS number SF8300000
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style="background: #F8EABA; text-align: center;" colspan="2" | Properties
Molecular formula C12H8N2
Molar mass 180.21 g/mol
Appearance colourless crystals
Density 1.31 g/cm3
Melting point

117 °C

Solubility in water moderate
Solubility in other solvents acetone
style="background: #F8EABA; text-align: center;" colspan="2" | Hazards
R-phrases R25, R50/53
S-phrases S45,S60,S61
style="background: #F8EABA; text-align: center;" colspan="2" | Related compounds
Related compounds 2,2'-bipyridine
 YesY (what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Phenanthroline (phen) is a heterocyclic organic compound. As a bidentate ligand in coordination chemistry, it forms strong complexes with most metal ions. In terms of its coordination properties, phen is similar to 2,2'-bipyridine (bipy).


Phenanthroline may be prepared by two successive Skraup reactions of glycerol with o-phenylenediamine, catalyzed by sulfuric acid, and an oxidizing agent, traditionally aqueous arsenic acid or nitrobenzene.[1] Dehydration of glycerol gives acrolein which condenses with the amine followed by a cyclization.

Peptidase inhibitor

1,10-Phenanthroline is an inhibitor of metallopeptidases, with one of the first observed instances reported in carboxypeptidase A.[2] Inhibition of the enzyme occurs by removal and chelation of the metal ion required for catalytic activity, leaving an inactive apoenzyme. 1,10-Phenanthroline targets mainly zinc metallopeptidases, with a much lower affinity for calcium.[3]

Ferroin and analogues

The complex [Fe(phen)3]2+, called "ferroin," is used for the photometric determination of Fe(II).[4] It is used as a redox indicator with standard potential +1.06 V. The reduced ferrous form has a deep red colour and the oxidised form is light-blue. Ferroin is used as a cell permeable inhibitor for metalloproteases in cell biology.

The pink complex [Ni(phen)3]2+ has been resolved into its Δ and Λ isomers.[5] The analogous [Ru(phen)3]2+ has long been known to be bioactive.[6]

Related ligands

In the related compound "bathophenanthroline," the 4 and 7 positions are substituted by phenyl groups.

As an indicator for alkyl lithium reagents

Alkyl lithium reagents form deeply colored derivatives with phenanthroline. The alkyl lithium content of solutions can be determined by treatment of such reagents with small amounts of phenanthroline (ca. 1 mg) followed by titration with alcohols to a colourless endpoint.[7]

Grignard reagents may be similarly titratred.[8]


  1. B. E. Halcrow, W. O. Kermack (1946). "43. Attempts to find new antimalarials. Part XXIV. Derivatives of o-phenanthroline (7 : 8 : 3′ : 2′-pyridoquinoline)". J. Chem. Soc.: 155–157. doi:10.1039/jr9460000155. 
  2. Felber, JP, Coombs, TL & Vallee, BL (1962). "The mechanism of inhibition of carboxypeptidase A by 1,10-phenanthroline". Biochemistry. 1: 231–238. doi:10.1021/bi00908a006. PMID 13892106. 
  3. Salvesen, GS & Nagase, H (2001). "Inhibition of proteolytic enzymes". Proteolytic enzymes: a practical approach, 2 edn. 1: 105–130. 
  4. Belcher, R. "Application of chelate Compounds in Analytical Chemistry" Pure and Applied Chemistry, 1973, volume 34, pages 13-27.
  5. George B. Kauffman, Lloyd T. Takahashi (1966). "Resolution of the tris-(1,10-Phenanthroline)Nickel(II) Ion". Inorg. Synth. 5: 227–232. 
  6. F. P. Dwyer, E. C. Gyarfas, W. P. Rogers, J. H. Koch (1952). "Biological Activity of Complex Ions". Nature. 170: 190–191. doi:10.1038/170190a0. 
  7. Paul J. Fagan and William A. Nugent (1998), "1-Phenyl-2,3,4,5-Tetramethylphosphole", Org. Synth. ; Coll. Vol., 9: 653  Missing or empty |title= (help)
  8. Ho-Shen Lin, Leo A. Paquette (1994). "A Convenient Method for Determining the Concentration of Grignard Reagents". Synth. Commun. 24: 2503–2506. doi:10.1080/00397919408010560. 

External Links

fr:1,10-phénantroline it:1,10-fenantrolina nl:Fenantroline ja:フェナントロリン pl:Fenantrolina pt:Fenantrolina fi:Fenantroliini zh:邻二氮菲