One pot synthesis of heterometallic 3d–3d azido architectures: assembling strategy and magnetic properties

The CuII ions usually have different coordinated geometry to other 3d ions, especially NiII and CoII ions, in azido–carboxylate mixed ligand systems. That provides a potential way to synthesize rare heterometallic 3d–3d azido complexes with peculiar magnetic properties. Assembling CuII, MII (M = Ni and Co), azido and nicotinic acid in hydrothermal condition, two novel isomorphic 3D heterometallic 3d–3d azido complexes, [CuM(N3)2(nicotinate)2]∞ (M = NiII for 1 and CoII for 2) were obtained. The structure of the complexes can be described as EO azido and syn,syn carboxylate mixed bridged spin sequence chains (–1/2–J1–1–J2–1/2– for 1 and –1/2–J1–3/2–J2–1/2– for 2) linked by the pyridyl groups. Dominant ferromagnetic interactions were observed between the CuII and MII ions in the chains despite the largest M–N–M angle of about 129° in the 3d metal azido–carboxylate mixed coordinated systems and weak antiferromagnetic interactions between the chains. At low temperature, a spin–flop phase transition was present in the CoII involved complex 2.