The design and synthesis of pyrazine amide ligands suitable for the “tiles” approach to molecular weaving with octahedral metal ions

The pyrazine-containing ligands 1 (pyrazine-2-carboxylic acid (pyridine-2-ylmethyl)-amide) and 2 (pyrazine-2,5-dicarboxylic acid bis-[(pyridine-2-ylmethyl)-amide]) have been synthesized and characterized in order to probe their ability to form polynuclear transition metal complexes. A mixed oxidation state Co3+–Co2+–Co3+ complex with deprotonated ligand 1, [Co(1−)2Co(H2O)2Cl2Co(1−)2]Cl2, has been obtained and characterized by X-ray crystal structure determination. The central octahedral cobalt(II) ion in the complex is coordinated by one pyrazine nitrogen from each of the surrounding octahedral cobalt(III), ions which are meridianally coordinated by two of the ligands 1−. Key aspects of both ligands are their rigid meridianal coordination, coupled with the pyrazine core, which demands coordination of metal ions on opposite sides of the ligand strand.