Self-assembly and magnetic properties of Ni(ii)/Co(ii) coordination polymers based on 1,4-bis(imidazol-1-yl)benzene and varying biphenyltetracarboxylates†
Abstract
Solvothermal or hydrothermal methods of M(NO3)2·6H2O (M = Ni(II) or Co(II)) with an N donor (1,4-bis(imidazol-1-yl)benzene, 1,4-bib) and auxiliary deprotonated biphenyltetracarboxylates (2,2′,5,5′-biphenyltetracarboxylic acid, H4(o,m-bpta); 3,3′,5,5′-biphenyltetracarboxylic acid, H4(m,m-bpta); or 3,3′,4,4′-biphenyltetracarboxylic acid, H4(m,p-bpta)) give five novel coordination polymers in H2O–DMF or H2O, namely, [Ni2(1,4-bib)3(o,m-bpta)(H2O)2] (1), [Ni2(1,4-bib)3(HCO2)4(H2O)2]·5H2O (2), [Co2(1,4-bib)2(m,m-bpta)(H2O)4] (3), [Ni2(1,4-bib)2(m,p-bpta)(H2O)2] (4) and [Co2(1,4-bib)2(m,p-bpta)(H2O)2] (5). The structural properties of the complexes have been acquired by single-crystal XRD and further characterized by EA, IR spectroscopy, powder XRD and TG analysis. The framework of 1 is constructed of a 3D interpenetration structure with a (4·62)2(42·62·82) topology. Complex 2 exhibits a 3D supramolecular framework assembled by 1D mutual interpenetration chains. Complex 3 generates a 3D supramolecular architecture from (4,4)-connected 2D layers. Complexes 4 and 5 exhibit isomorphism, having 2D sheet structures with (4,4)-grid units. These results reveal that the 1,4-bib ligand cooperating with different biphenyltetracarboxylic acids can be used as versatile building blocks for the construction of metal–organic frameworks. Magnetic susceptibility measurements indicate the presence of weak ferromagnetic exchanges between adjacent Ni(II) ions with g = 2.235(5), 2.223(7) and J = 0.906(1), 2.220(1) cm−1 for 1 and 4, respectively.