Pyridine-2,6-dicarboxamide pincer-based macrocycle: a versatile ligand for oxoanions, oxometallates, and transition metals^*

*This paper is dedicated to the memory of Dr. Sanjib Ghosh, an excellent chemist and human being who was the inspiration for this study.

Abstract

A tetracarboxamide-based macrocycle has shown a general aptitude for binding both anions and metal cations. Crystallographic studies indicate that in several instances quite similar structures are obtained. The macrocycle can be readily synthesised by a one-step condensation. Smaller oxoanions (sulfate, oxalate, and nitrite) bind within a folded macrocyclic cleft. Larger oxoanions and oxometallates (dihydrogen phosphate, dichromate, and perrhenate) dangle below the folded macrocycle. Smaller divalent metal ions (nickel(II) and copper(II)) form binuclear complexes with the metal ions bound within the folded macrocycle. The larger palladium(II) also forms a ditopic complex with the two pincers units, but the macrocycle lies in a more planar, non-folded conformation.

Keywords:

• Pyridine-2,6-dicarboxamide macrocycle
• oxoanion host
• oxometallate host
• transition metal complexes
• supramolecular coordination chemistry

Notes

* This paper is dedicated to the memory of Dr. Sanjib Ghosh, an excellent chemist and human being who was the inspiration for this study.