Impact of N-donor auxiliary ligands on two new Co(ii)-based MOFs with N-heterocyclic ligands and a magnetism study

Abstract

Two new cobalt(II) MOFs, namely [Co₂(L)₂(4,4′-bipy)]_n (1) and {[Co(L)(dib)_0.5(H₂O)₂]·H₂O}_n (2), were obtained by the self-assembly of Co(NO₃)₂·6H₂O with V-shaped 2,4-[6-(4-carboxyphenyl)pyrazin-2-yl]benzoic acid (H₂L) in the presence of two bridging auxiliary N-donor linkers, 1,4-di(1H-imidazole-1-yl) benzene (dib) and 4,4′-bipyridine (4,4′-bipy). 1 is a 3D (3,4)-connected framework containing 2-fold interpenetration, while 2 features an infinite 2D network structure with [Co₂(μ₂-O)₂]⁴⁺ subunits. The structural diversity of the two MOFs suggests that different auxiliary linkers can induce different conformations and coordination modes of H₂L and have an influence on the resulting networks. A computational study of Hirshfeld surface analysis was also conducted. In addition, the magnetic properties of 1 and 2 were investigated in detail, which revealed the ferromagnetic and antiferromagnetic interactions that occurred between Co(II) centers in 1 and 2, respectively.