Synthesis and structural characterization of a novel seven-coordinate cobalt(II) complex: 2,9-Bis(ethanolamine)-1,10-phenanthrolinechlorocobalt(II) chloride

Condensation reaction of 2,9-dicarboxaldehyde-1,10-phenanthroline with 2-aminoethanol followed by NaBH4 reduction yielded the polydentate Schiff base ligand 2,9-bis(ethanolamine)-1,10-phenanthroline in its reduced form. This ligand was characterized by elemental analysis, LC–MS, IR, UV–Vis and NMR spectroscopy. Reaction of the reduced Schiff base ligand with aqueous solution of cobalt(II) chloride affords 2,9-bis(ethanolamine)-1,10-phenanthrolinechlorocobalt(II) chloride in high yield. Single crystals of the cobalt(II) complex were obtained from the crystallization in ethanol and its structure was elucidated by X-ray structural analysis. The cobalt(II) complex ion was found to be seven-coordinated in a pentagonal bipyramidal geometry, whereby cobalt(II) ion is surrounded by the six donor atoms in the ligand molecule and a chloride ion.

Graphical abstractWe report here the syntheses of a 1,10-phenanthroline derivative polydentate Schiff base ligand 2,9-bis(ethanolamine)-1,10-phenanthroline in its reduced form and its pentagonal bipyramidal cobalt(II) complex. Structure of cobalt(II) complex was also resolved by single-crystal X-ray diffraction analysis.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Novel polydentate Schiff base ligand was synthesized in its reduced form. ► A pentogonal bipyramidal cobalt(II) complex was obtained. ► Structure of cobalt(II) complex was resolved by single-cyrstal X-ray diffraction analysis. ► This work offers a new approach for the design of metal-organic functional materials.