Sample of 1,10-Phenanthroline
Preferred IUPAC name
3D model (JSmol)
ECHA InfoCard 100.000.572 Edit this at Wikidata
EC Number
  • 200-629-2
  • monohydrate: 627-114-9
RTECS number
  • SF8300000
UN number 2811
  • InChI=1S/C12H8N2/c1-3-9-5-6-10-4-2-8-14-12(10)11(9)13-7-1/h1-8H checkY
  • InChI=1/C12H8N2/c1-3-9-5-6-10-4-2-8-14-12(10)11(9)13-7-1/h1-8H
  • c1cc2ccc3cccnc3c2nc1
  • monohydrate: C1=CC2=C(C3=C(C=CC=N3)C=C2)N=C1.O
Molar mass 180.21 g/mol
Appearance colourless crystals
Density 1.31 g/cm3
Melting point 118.56 °C (245.41 °F; 391.71 K)[2]
Boiling point 409.2[2]
Solubility in other solvents acetone, ethanol[2]
Acidity (pKa) 4.84 (phenH+)[2]
Occupational safety and health (OHS/OSH):
Main hazards
mild neurotoxin, strong nephrotoxin, and powerful diuretic
GHS labelling:
GHS06: ToxicGHS09: Environmental hazard
H301, H410
P264, P270, P273, P301+P310, P321, P330, P391, P405, P501
Related compounds
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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1,10-Phenanthroline (phen) is a heterocyclic organic compound. It is a white solid that is soluble in organic solvents. The 1,10 refer to the location of the nitrogen atoms that replace CH's in the hydrocarbon called phenanthrene.

Abbreviated "phen", it is used as a ligand in coordination chemistry, forming strong complexes with most metal ions.[3][4] It is often sold as the monohydrate.


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.[5] Dehydration of glycerol gives acrolein which condenses with the amine followed by a cyclization.

Coordination chemistry

In terms of its coordination properties, phenanthroline is similar to 2,2'-bipyridine (bipy) with the advantage that the two nitrogen donors are preorganized for chelation. Phenanthroline is a stronger base than bipy. According to one ligand ranking scale, phen is a weaker donor than bipy.[6]

Several homoleptic complexes are known of the type [M(phen)3]2+. Particularly well studied is [Fe(phen)3]2+, called "ferroin." It can be used for the photometric determination of Fe(II).[7] 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.[8] The pink complex [Ni(phen)3]2+ has been resolved into its Δ and Λ isomers.[9] The complex [Ru(phen)3]2+ is bioactive.[10]

Copper(I) forms [Cu(phen)2]+, which is luminescent.[11][12]

Bioinorganic chemistry

1,10-Phenanthroline is an inhibitor of metallopeptidases, with one of the first observed instances reported in carboxypeptidase A.[13] 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.[14]

Related phen ligands

A variety of substituted derivatives of phen have been examined as ligands.[12][15] Substituents at the 2,9 positions confer protection for the attached metal, inhibiting the binding of multiple equivalents of the phenanthroline. Such bulky ligands also favor trigonal or tetrahedral coordination at the metal.[16] Phen itself form complexes of the type [M(phen)3]Cl2 when treated with metal dihalides (M = Fe, Co, Ni). By contrast, neocuproine and bathocuproine form 1:1 complexes such as [Ni(neocuproine)Cl2]2.[17]

Basicities of 1,10-Phenanthrolines and 2,2'-Bipyridine[18]
phen derivative pKa comment/alt. name numbering scheme
1,10-phenanthroline 4.86 phen Numbering for 1,10-phenanthroline derivatives.
2,2'-bipyridine 4.30 bipy
5-nitro-1,10-phenanthroline 3.57
2,9-dimethyl-1,10-phenanthroline unknown neocuproine[19][20]
2,9-Dimethyl-4,7-diphenylphenanthroline unknown Bathocuproine[19][21]
4,7-dimethyl-1,10-phenanthroline 5.97
4,7-diphenyl-1,10-phenanthroline unknown bathophenanthroline[22]
5,6-dimethyl-1,10-phenanthroline 5.20 5,6-Me2phen
3,4,7,8-tetramethylphenanthroline 6.31 3,4,7,8-Me4phen[23]
4,7-dimethoxy-1,10-phenanthroline 6.45 4,7-(MeO)2phen[24]
2,6-dimesitylphenanthroline unknown HETPHEN[25][16]

As an indicator for alkyllithium reagents

Alkyllithium reagents form deeply colored derivatives with phenanthroline. The alkyllithium 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.[26] Grignard reagents may be similarly titrated.[27]

See also


  1. ^ Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 211. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
  2. ^ a b c d e Haynes, William M., ed. (2016). CRC Handbook of Chemistry and Physics (97th ed.). CRC Press. p. 3.444. ISBN 978-1-4987-5429-3.
  3. ^ Luman, C.R. and Castellano, F.N. (2003) "Phenanthroline Ligands" in Comprehensive Coordination Chemistry II. Elsevier. ISBN 978-0-08-043748-4.
  4. ^ Sammes, Peter G.; Yahioglu, Gokhan (1994). "1,10-Phenanthroline: A versatile ligand". Chemical Society Reviews. 23 (5): 327. doi:10.1039/cs9942300327.
  5. ^ Halcrow, Barbara E.; Kermack, William O. (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. PMID 20983293.
  6. ^ Teng, Qiaoqiao; Huynh, Han Vinh (2017). "A Unified Ligand Electronic Parameter Based on C NMR Spectroscopy of N-Heterocyclic Carbene Complexes". Dalton Transactions. 46 (3): 614–627. doi:10.1039/C6DT04222H. PMID 27924321.
  7. ^ Belcher R (1973). "Application of chelate Compounds in Analytical Chemistry". Pure and Applied Chemistry. 34: 13–27. doi:10.1351/pac197334010013. S2CID 44054260.
  8. ^ Bellér, G. B.; Lente, G. B.; Fábián, I. N. (2010). "Central Role of Phenanthroline Mono-N-oxide in the Decomposition Reactions of Tris(1,10-phenanthroline)iron(II) and -iron(III) Complexes". Inorganic Chemistry. 49 (9): 3968–3970. doi:10.1021/ic902554b. PMID 20415494.
  9. ^ George B. Kauffman; Lloyd T. Takahashi (1966). "Resolution of the tris-(1,10-Phenanthroline)Nickel(II) Ion". Inorganic Syntheses. Vol. 5. pp. 227–232. doi:10.1002/9780470132395.ch60. ISBN 978-0-470-13239-5.
  10. ^ Dwyer, F. P.; Gyarfas, Eleonora C.; Rogers, W. P.; Koch, Judith H. (1952). "Biological Activity of Complex Ions". Nature. 170 (4318): 190–191. Bibcode:1952Natur.170..190D. doi:10.1038/170190a0. PMID 12982853. S2CID 6483735.
  11. ^ Armaroli N (2001). "Photoactive Mono- and Polynuclear Cu(I)-Phenanthrolines. A Viable Alternative to Ru(Ii)-Polypyridines?". Chemical Society Reviews. 30 (2): 113–124. doi:10.1039/b000703j.
  12. ^ a b Pallenberg A. J.; Koenig K. S.; Barnhart D. M. (1995). "Synthesis and Characterization of Some Copper(I) Phenanthroline Complexes". Inorganic Chemistry. 34 (11): 2833–2840. doi:10.1021/ic00115a009.
  13. ^ Felber, Jean-Pierre; Coombs, Thomas L.; Vallee, Bert L. (1962). "The mechanism of inhibition of carboxypeptidase A by 1,10-phenanthroline". Biochemistry. 1 (2): 231–238. doi:10.1021/bi00908a006. PMID 13892106.
  14. ^ Salvesen, GS & Nagase, H (2001). "Inhibition of proteolytic enzymes". In Beynon, Rob & Bond, J S (eds.). Proteolytic Enzymes: A Practical Approach. Vol. 1 (2nd ed.). Oxford University Press. pp. 105–130. ISBN 978-0-19-963662-4.
  15. ^ Accorsi, Gianluca; Listorti, Andrea; Yoosaf, K.; Armaroli, Nicola (2009). "1,10-Phenanthrolines: Versatile building blocks for luminescent molecules, materials and metal complexes". Chemical Society Reviews. 38 (6): 1690–2300. doi:10.1039/B806408N. PMID 19587962.
  16. ^ a b Somerville, Rosie J.; Odena, Carlota; Obst, Marc F.; Hazari, Nilay; Hopmann, Kathrin H.; Martin, Ruben (2020). "Ni(I)–Alkyl Complexes Bearing Phenanthroline Ligands: Experimental Evidence for CO2 Insertion at Ni(I) Centers". Journal of the American Chemical Society. 142 (25): 10936–10941. Bibcode:2020JAChS.14210936S. doi:10.1021/jacs.0c04695. PMC 7351122. PMID 32520556.
  17. ^ Preston, H. S.; Kennard, C. H. L. (1969). "Crystal Structure of di-mu-Chloro-sym-trans-Dichloro-Bis-(2,9-Dimethyl-1,10-Phenanthroline)dinickel(II)-2-Chloroform". J. Chem. Soc. A: 2682–2685. doi:10.1039/J19690002682.
  18. ^ Leipoldt, J.G.; Lamprecht, G.J.; Steynberg, E.C. (1991). "Kinetics of the substitution of acetylacetone in acetylactonato-1,5-cyclooctadienerhodium(I) by derivatives of 1,10-phenantrholine and 2,2-dipyridyl". Journal of Organometallic Chemistry. 402 (2): 259–263. doi:10.1016/0022-328X(91)83069-G.
  19. ^ a b Rezazadeh, Sina; Devannah, Vijayarajan; Watson, Donald A. (2017). "Nickel-Catalyzed C-Alkylation of Nitroalkanes with Unactivated Alkyl Iodides". Journal of the American Chemical Society. 139 (24): 8110–8113. doi:10.1021/jacs.7b04312. PMC 5531607. PMID 28594543.
  20. ^ Nilsson, Peter (2012). "Neocuproine". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rn01440. ISBN 978-0-471-93623-7.
  21. ^ Liu, Guosheng; Wu, Yichen (2012). "Bathocuproine". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rn01392. ISBN 978-0-471-93623-7.
  22. ^ Vallée, Frédéric; Kühn, Fritz E.; Korinth, Valentina A. (2013). "Bathophenanthroline". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rn01319.pub2. ISBN 978-0-471-93623-7.
  23. ^ Zhu, Lingui; Altman, Ryan A. (2013). "3,4,7,8-Tetramethyl-1,10-phenanthroline (Tmphen)". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rn01515. ISBN 978-0-471-93623-7.
  24. ^ Altman, Ryan A. (2008). "1,10-Phenanthroline, 4,7-Dimethoxy". Encyclopedia of Reagents for Organic Synthesis. eEROS. doi:10.1002/047084289X.rn00918. ISBN 978-0-471-93623-7.
  25. ^ Kohler, Lars; Hayes, Dugan; Hong, Jiyun; Carter, Tyler J.; Shelby, Megan L.; Fransted, Kelly A.; Chen, Lin X.; Mulfort, Karen L. (2016). "Synthesis, structure, ultrafast kinetics, and light-induced dynamics of CuHETPHEN chromophores". Dalton Transactions. 45 (24): 9871–9883. doi:10.1039/c6dt00324a. PMID 26924711.
  26. ^ Fagan, Paul J.; Nugent, William A. (1998). "1-Phenyl-2,3,4,5-Tetramethylphosphole". Organic Syntheses; Collected Volumes, vol. 9, p. 653.
  27. ^ Lin, Ho-Shen; Paquette, Leo A. (1994). "A Convenient Method for Determining the Concentration of Grignard Reagents". Synth. Commun. 24 (17): 2503–2506. doi:10.1080/00397919408010560.