4-Substituent pyridine directed cobalt(ii) azides: solvothermal synthesis, structure, and magnetic properties

Abstract

The structure and magnetism of three cobalt(II)–azide complexes, [Co(N₃)₂(bepy)₂]_n (1), [Co₂(N₃)₄(vipy)₄]_n (2), and [Co(N₃)₂(bipy)]_n (3) were tuned by three structurally related 4-substituent pyridines, 4-benzylpyridine (bepy), 4-vinyl pyridine (vipy), and 4,4′-bipyridine (bipy) as co-ligands in solvothermal reactions. With flexible benzyl as a substituent group of the pyridine co-ligand, a one-dimensional (1D) complex 1 with double end-to-end (EE) azide-bridging Co(II) chain is formed. While using a rigid but small vinyl group as the substituent, a distinct Co(II)–azide chain with alternate double end-on (EO) and double EE azide bridges was obtained. Finally, when another pyridine group was used instead of the substituent incapable of coordinating in 1 and 2, a bipyridine, it gave rise to a chiral complex 3 with a three-dimensional (3D) diamondoid Co(II)–azide framework further reinforced by the bipy ligand. Magnetic studies indicate antiferromagnetic interactions between the Co(II) ions in the three complexes, but interestingly, weak antiferromagnetism origin of spin canting exists in 3 at low temperatures.