Preparation and separation of mixed-ligand Fe(II) complexes containing 1,10-phenanthroline-5,6-dione as ligand

Abstract

The synthesis, separation, and characterization of mixed-ligand iron(II) complexes containing 1,10-phenanthroline (phen), 1,10-phenanthroline-5,6-dione (pdon), and NCS⁻ are reported. The mixed-ligand complexes [Fe(phen)(pdon)₂]²⁺ and [Fe(phen)₂(pdon)]²⁺ were prepared from iron(II) sulfate hepta hydrate and both ligands. The mixture of both complexes formed regardless the ratio of the ligands or the reaction time; therefore, the complexes were separated successfully on the reversed phase (RP) Develosil RP-Aqueous [C30] 5 µm, 150 × 4.6 mm column by two different methods. The first method was the ion paired RP chromatography performed under gradient elution with acetonitrile–water containing 0.001 mol L⁻¹ KPF₆ aqueous as mobile phases. The second method was the RP chromatography performed under gradient elution with methanol and water as mobile phases. The gradient elution with water–methanol as eluents was preferred for the semi preparative separations allowing one to use the complexes without further purification upon separation, different than the first method and its variations so far. Three complexes (5, 6, and 7) were characterized by electrospray ionization mass spectrometry, NMR, UV-Vis, and IR.

Keywords:

• Mixed-ligand iron(II) complexes
• 1,10-Phenanthroline-5,6-dione
• Synthesis
• LC-MS

Acknowledgments

This work was supported by the Ministry of Science, Education, and Sports of the Republic of Croatia (Project No. 098-0982904-2927). The financial support of the funding institution is gratefully acknowledged.