Three coordination frameworks with copper formate based low dimensional motifs: synthesis, structure and magnetic properties

Abstract

In this study we report the synthesis, crystal structures and magnetic properties of three frameworks wherein Cu cations are bridged by formate linkers into one-dimensional motifs. One of these compounds, Cu₂(HCO₂)₃(C₃N₂H₄)₄(NO₃), contains a ladder motif but remains paramagnetic to 2 K. This is likely because of the longer superexchange pathway along its chains due to the orientation of the Jahn–Teller axis of its Cu cations. In contrast Cu(HCO₂)(NO₃)(NH₃)₂ and Cu(HCO₂)(ClO₄)(NH₃)₂ feature Cu(HCO₂) chains in which the Jahn–Teller axis is oriented perpendicular to the chain direction; these exhibit antiferromagnetic order below 12 and 7 K, respectively. Their magnetic susceptibilities are well fitted by a one-dimensional chain model but further examination of their magnetic properties reveals significant inter-chain magnetic coupling and a lack of spin dynamics. This suggests that these transitions correspond to the emergence of long-range magnetic order, highlighting the importance of detailed studies of frameworks containing low dimensional motifs to gain a deeper understanding of their magnetic behaviour.