ANTIFERROMAGNETISM TUNED BY THE TOPOLOGY OF THE INTERVENING BRIDGING LIGAND - CRYSTAL-STRUCTURE AND MAGNETIC-PROPERTIES OF THE (MU-PHTHALATO)([BIS(PIPERIDINE)]CU(II)) CHAIN COMPLEX

The crystal structure of the chain complex [(mu-phth)(pip)2Cu]n, where phth is the dianion of phthalic acid and pip is piperidine, has been determined by single crystal X-ray methods. The complex crystallizes in the monoclinic space group I2/a with a=15.853(2), b=10.785(1), c=11.629(1) angstrom, beta=111.321(3)-degrees, Z=4 and V=1852.11 angstrom3. Solution of the structure led to final values of R=0.0298 and R(w)=0.0330 with 167 least-squares parameters for 1578 unique reflections with F(o)>6.5sigma(F(o)). The compound is a chain copper(II) complex, [(pip)2Cu(mu-phth)]n being the polymeric entity. Within the chain the copper(II) ions are bridged by the phth ligand in an anisobidentate fashion, the coordination geometry about each Cu(II) ion is distorted octahedral; two nitrogen atoms belonging to two piperidine molecules along with two carboxylato oxygen atoms of two different phthalato bridges occupy the equatorial positions, whereas the two remaining oxygen atoms of the same carboxylato groups occupy the axial positions. Thus, chains along the c direction are formed. The intrachain metal-metal separation is 5.814 angstrom. The variable-temperature (4.2-290 K) magnetic susceptibility data of the complex showed a perfect Curie law. The role of the topology of the intervening bridge on the strength of the antiferromagnetic coupling of the complex is discussed.