For many years, 1,10-phenanthroline has been used as a ligand in the detection and quantification of iron via UV/visible spectrophotometry. The main species in the quantification of iron is the [Fe(phen)3] 2+ cation, which absorbs at 510 nm. 1,2 Our laboratory has been interested in the synthesis of mixed-ligand complexes with 2,6-pyridinedicarboxylic acid (dipicolinic acid, H2dipic) in the interest of making supramolecular complexes. We decided to repeat the synthesis of the mixed ligand complexes as reported by Samnani et al.,3 where they claimed to have synthesised [Fe(dipic)(phen)] n+ , but that species was not structurally characterized. We, instead serendipitously isolated the title complex, tris(1,10-phenanthroline)iron(II) perchlorate ethanol monosolvate hemihydrate, from a reaction mixture consisting of dipicolinic acid, 1,10-phenanthroline, and iron(III) perchlorate hexahydrate. While the fate of all of the solution species is not yet known, the reduction of metal centers with ethanol to form acetaldehyde is well established. 4 In this discussion, we now report the unusual synthesis and crystal structure of the title complex, and compare the tris(1,10-phenanthroline)iron(II) cation to the many tris(1,10-phenanthroline)iron(II) cations already reported.The synthesis of the title complex included analytical grade reagents. 2,6-Pyridinedicarboxylic acid (0.17 g, 1 mmol) in ethanol (50 cm 3 ) was added dropwise into a stirred solution of iron(III) perchlorate hexahydrate (0.35 g, 1 mmol) in ethanol (50 cm 3 ) in a 250 cm 3 conical flask over a 30 min period at 60 C. The resulting mixture was stirred for an additional hour after the complete addition of 2,6-pyridinedicarboxylic acid. A solution of 1,10-phenanthroline (0.18 g, 1 mmol) in ethanol (50 cm 3 ) was added dropwise into the above solution, which was then stirred for three hours. The title complex was serendipitously obtained by reacting dipicolinic acid, 1,10-phenanthroline, and iron(III) perchlorate hexahydrate in ethanol. Single crystals were grown by allowing the sealed reaction mixture to stand for two weeks, thus yielding the increasingly structurally characterized tris(1,10-phenanthroline)iron(II) cation.
