Cobalt(ii)–(dpyo)–dicarboxylate networks: unique H-bonded assembly and rare bridging mode of dpyo in one of them [dpyo = 4,4′-dipyridyl N,N′-dioxide]

Abstract

Polymeric networks, {[Co(dpyo)(ox)]}_n (1), {[Co(dpyo)(fum)(H₂O)₂]}_n (2) and {[Co(dpyo)(tp)(H₂O)₂]·[Co(H₂O)₆]·(tp)·(H₂O)}_n (3) [ox = oxalate dianion, fum = fumarate dianion, tp = terephthalate dianion and dpyo = 4,4′-dipyridyl N,N′-dioxide] have been synthesized and characterized by single crystal X-ray diffraction analyses. The structural determination reveals 1 and 2 are covalent bonded 2D networks of 4,4 topology and of these, complex 2 undergoes a H-bonding scheme resulting in a 3D supramolecular architecture. Complex 3 is a 1D coordination polymer built up by almost collinear hexacoordinated Co(II), doubly bridged by a tp carboxylate group and a dpyo oxygen, which in combination with lattice [Co(H₂O)₆]²⁺, tp and water molecules shows an unprecedented 3D supramolecular network through H-bonding. In the polymer the dpyo shows novel µ-4,4 bridging mode towards the cobalt ion. Low temperature magnetic interaction reveals antiferromagnetic coupling in all of the complexes.