Supramolecular isomers of metal–organic frameworks: the role of a new mixed donor imidazolate-carboxylate tetradentate ligand

Abstract

Five new metal–organic frameworks prepared from the ligand 5-bis(3-(1-imidazolyl)propylcarbamoyl)terephthalate (bipta²⁻) and transition metal salts, Zn²⁺ (1), Co²⁺ (2), Mn²⁺ (3, 4) and Cu²⁺ (5), are reported. Single crystal X-ray studies reveal that the bipta²⁻ ligand acts as a tetradentate ligand and combines with four-coordinate cationic metal nodes to give four-connected framework structures. Whilst reaction of bipta²⁻ with Zn(II) gives rise to a framework of diamondoid topology 1, the analogous frameworks with Co(II), Mn(II) and Cu(II) afford frameworks that incorporate square-planar nodes. Whereas 2 and 5 form frameworks of Cd(SO₄) (cds) and square 4⁴ nets (sql), respectively, reaction of Mn(II) with bipta²⁻ forms two supramolecular isomers of topology cds for 3 and sql for 4.