Metal–ligand ratio-controlled assembly of two pairs of Co(ii) complexes: syntheses, structures and magnetic properties

Reactions of Co(II) salts with rigid 5-amino-isophthalic acid (AIP) and flexible bis(imidazole) ligands by controlling the metal–ligand ratio gave rise to two pairs of new complexes: [Co(AIP)(bimb)] (1) and [Co(AIP)(bimb)0.5] (2), [Co(AIP)(bix)]·H2O (3) and [Co2(AIP)2(bix)1.5] (4) (bimb = 1,4-bis (imidazol-1-yl)-butane, bix = 1,4-bis(imidazol-1-yl-methylene)-benzene). Comparative study revealed that the different metal–ligand ratios affected the coordination modes of the ligand and thus resulted in four different structures. All complexes display 2D structures and extend into 3D supramolecular frameworks via intermolecular hydrogen bonds. Complex 1 features a (4,5)-connected hydrogen-bond network. Complex 2 displays a 2D bilayered structure with a rare (3,4)-connected (63)(65 ·8) topology. Complex 3 is an 2D (4,4) network showing 2-fold parallel interpenetrating 2D → 2D structure, which features the 2-fold interpenetrating cds hydrogen-bond net. Complex 4 shows a trinodal (4,4,5)-connected hydrogen-bond net. Magnetic studies of 1 reveal ferromagnetic interaction at low temperature and 4 displays antiferromagnetic behavior.