Hydrothermal syntheses, crystal structures and magnetic properties of two copper(ii) complexes involved in situligand synthesis

Abstract

The hydrothermal reaction of Cu(NO₃)₂, isophthalate (ip) and 2,2′-bipyridine (2,2′-bpy) without or with K₂Cr₂O₇ affords different complexes, whose structures are controlled only by the addition of the K₂Cr₂O₇. The reaction of Cu(NO₃)₂, isophthalate and 2,2′-bipyridine yields a novel one-dimensional double-chain coordination polymer [Cu₃(ip)₂(Hipa)₂(bpy)₂]_n (1). However, with the addition of K₂Cr₂O₇ in the above reaction at the same hydrothermal conditions, a discrete hexanuclear Cu(II) complex [Cu₆(ipO)₄(2,2′-bpy)₂(H₂O)₂]·6H₂O (2) (ipOH = 2-hydroxyisophthalate) was isolated. It is interesting to find that the in situ reaction of isophthalate (ip) oxidized to 2-hydroxyisophthalate (ipOH) occurs. K₂Cr₂O₇ acts as an oxidant. The magnetic properties of 1 and 2 have been investigated by variable-temperature magnetic susceptibility and magnetization measurements, and the results reveal that intramolecular ferromagnetic interactions exist with weak intermolecular antiferromagnetic interactions at very low temperature in 1 and weak antiferromagnetic interactions admixture with strong ferromagnetic interactions in 2.