Diverse manganese(ii) coordination polymers derived from achiral/chiral imidazolium-carboxylate zwitterions and azide: structure and magnetic properties

Abstract

Five Mn(II) coordination polymers containing azide and carboxylate as simultaneous bridges have been derived from different imidazolium-carboxylate zwitterionic ligands: 1-methyl-3-(carboxylatomethyl)imidazolium (L¹), 1,3-bis(carboxylatomethyl)imidazolium (L²), (S,S)-, (R,R)-, and (R,S)-1,3-bis(1-carboxylatoethyl)imidazolium (S,S-L³, R,R-L³ and R,S-L³). The compounds are formulated as [Mn(L¹)(N₃)₂] (1), [Mn(L²)(N₃)] (2), [Mn(R,R-L³)(N₃)]·0.5CH₃OH (3-R), [Mn(S,S-L³)(N₃)]·0.5CH₃OH (3-S), [Mn(R,S-L³)(N₃)] (4). In compound 1, the neutral monocarboxylate zwitterion ligand (L¹) leads to uniform chains with bis(azide)(carboxylate) bridges. For compounds 2–4, the anionic dicarboxylate zwitterions L² and L³ lead to (azide)bis(carboxylate) bridges, but the overall coordination networks are different. In 2 and 3-S (or 3-R), chains with the (azide)bis(carboxylate) bridges are connected by L² and S,S-L³ (or R,R-L³), respectively, to give achiral and chiral 2D coordination networks with different connecting topologies. In compounds 4, which is derived from the mesomeric ligand R,S-L³, linear trinuclear units with the (azide)bis(carboxylate) bridges are linked by μ-1,3 azides to give 2D layers, and the layers are pillared into a 3D framework by the 1,3-dimethyleneimidazolium tethers. Magnetic analyses suggested that compounds 1–3 behave as 1D antiferromagnetic systems, while 4 shows canted antiferromagnetism with weak ferromagnetic ordering below T_C = 12.4 K.