Metal–organic coordination frameworks assembled with the long flexible ligand 4,4′-bis(imidazol-1-ylmethyl)biphenyl

Abstract

Nine novel coordination polymers have been obtained from the self-assembly reactions of the flexible ligand 4,4′-bis(imidazol-1-ylmethyl)biphenyl (bimb) with different metal salts and their structures and supramolecular architectures have been characterized by single crystal X-ray analysis. Three of them contain 1D polymers, namely [Cd(bimb)(OTs)₂(H₂O)₂] (3), [Cd(bimb)₂(H₂O)₂](OTs)₂·4MeOH (4) and [Cu(bimb)₂(H₂O)₂](SO₄)·2H₂O·2(acetone) (7), consisting of single-stranded chains (3) or ribbons of rings (4 and 7) that are joined viaH-bond bridges to give layers of (4,4) topology (sql). Three polymeric products contain 2D frameworks, i.e. the two nitrate species [Cd(bimb)₂(NO₃)₂] (2) and [Cu(bimb)₂(NO₃)₂] (8), that are isostructural and contain flat sql layers, and [Zn₂(bimb)₃(SO₄)₂]·(bimb)·Solv (9), comprised of interdigitated (6,3) honeycomb-like (hcb) layers threaded by the free bimb ligands. Also three 3D networks have been isolated, namely [Cd(bimb)(H₂O)(SO₄)]·Solv (1), containing 1D Cd(bimb) undulated single chains that are cross-linked by bridging sulfate anions and water molecules to give an overall 3D array with the diamond topology (dia), [Co(bimb)₂(SO₄)] (5) that consists of ribbons of rings spanning two distinct directions of propagation bridged by the sulfate anions to generate a 3D single net with the CdSO₄ type topology (cds), and [Co₂(bimb)₅(H₂O)₂](NO₃)₄·4EtOH·2H₂O (6), the first case of a 3D network assembled exclusively with the use of the bimb spacer, that contains ribbons and single chains cross-linked to give an overall 3D single cds array. Three forms of the uncoordinated ligand, i.e. bimb, bimb·H₂O and [bimbH](PF₆), were also isolated and structurally characterized to obtain a more complete information about the conformations of the bimb molecule.