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.[1] [2] 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.[3] Dehydration of glycerol gives acrolein which condenses with the amine followed by a cyclization.
Oxidation of 1,10-phenanthroline with a mixture of nitric and sulfuric acids gives 1,10-phenanthroline-5,6-dione.[4]
1,10-Phenanthroline forms many coordination complexes. One example is the iron complex called ferroin.
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. Grignard reagents may be similarly titrated.[5]