CRYSTAL STRUCTURES OF COPPER COMPLEXES SHOWING FERROMAGNETIC INTERACTION. M. Yasui, Y. Ishikawa, T. Nogami, T. Ishida and F. Iwasaki, Dept. of Applied Physics and Chemistry, The Univ. of Electro-Communications, Chofu, Tokyo 182, Japan
We have determined the crystal structures of copper(II) complexes coordinated with pyrimidine derivatives showing ferromagnetic interactions. [Cu(hfac)2(quinazoline)] (I), [Cu(hfac)2(pyrimidine)] (II), [Cu(hfac)2(4-methylpyrimidine)] (III), where hfac is 1,1,1,5,5,5-hexafluoropentane-2,4-dionate, [Cu(NO3)2(pyrimidine)2] (IV), and [Cu(NO3)2 (pyrimidine) (H2O)2] (V). For I, the ferromagnetic transition was observed at about 0.12K [Ishida et al., Synthetic Metals, 71, 1791 (1995)]. The ferromagnetic interaction was observed for II, III, and IV.
X-ray analysis revealed that the crystals of III have two modifications, a polymer structure [{Cu(hfac)2(4-methylpyrimidine)} n] (IIIa), and a trinuclear complex [{Cu(hfac)2} 3(4-methylpyrimidine)2] (IIIb).
All complexes, except for IIIb, form one-dimensional polymer structures in which the quinazoline or pyrimidine derivatives play a role of a bridging ligand. For I, two bridging ligands coordinate a Cu atom on both axial positions. The hfac ligands coordinate in an equatorial plane. Thus the Cu atom has a distorted octahedral structure. The complex V has a similar polymeric structure with two nitrates and two water molecules. In II and IIIa, which have also one-dimensional polymer structures with a distorted octahedral Cu, two bridging pyrimidine moieties are cis to one another. A Cu atom of IV is penta-coordinated with two bridging pyrimidines, one non-bridging pyrimidine and two nitrates. One nitrogen atom of non-bridging pyrimidine is free. The complex IIIb has a trinuclear structure. The central Cu atom has an octahedral structure while the terminal Cu atoms have a penta-coordinated square-pyramidal structure. The one-dimensional structure may be related to the ferromagnetic interaction except for V.