Tetra- And di-nuclear copper(II) complexes with stereoisomers of sulfinylcalix[4]arene arising from the disposition of four S=0 groups

A systematic investigation was conducted on the structures of tetra- and di-nuclear copper(II) complexes with three stereoisomers of sulflnylcalix[4] arenes (H₄L), the isomerism of which is determined by the disposition of the sulfinyl oxygen with respect to a reference oxygen from the mean plane containing four sulfur atoms. The sulfinylcalix[4]arene with a trans-cis-trans S-0 orientation H₄L^rtct reacted with Cu(OAc)₂ to form [Cu^II₄(L^rtct)(OAc)₃(μ- MeO)(MeOH)] (1), in which L^rtct4- adopts a cone conformation to afford tetrakis/aotridentate coordination through four phenoxo oxygens and four sulfinyl groups giving a square Cu^II₄ core. Ligands H ₄L^rccc and H₄L^rctt having cis-cis-cis and cis-trcms-trans configurations formed [Cu^II ₄(L^rccc)(OAc)₃(μ-OH)] (2) and [Cu ^II₄(L^rctt)(OAc)₃(μ-OH)] (3), respectively, which have common features, such as a cone-type conformation of L^4-, tetrakis fac-tri dentate coordination fashion, and tetra- copper(II) core in a square-pyramidal geometry. The similarities among 1-3 clearly show that sulfinylcalix[4]arenes can coordinate to Cu^II in a fac-tridentate fashion via a donor atom X (O or S) from a sulfinyl group and two flanking phenoxo O^-s and that X is simply determined by the X-Cu distance. Using [Cu(acac)?] as a copper(II) source, H₄L ^rctt formed [Cu^II₂(H₂L ^rctt)₂] (4), suggesting the significance of auxiliary ligand for bridging copper(II) centers to assemble the core, that is, the acetato ligands in complexes 1-3 are needed to form the core structure. Metal-metal interactions were investigated by means of magnetic susceptibility, and it was found that both ferro- and antiferromagnetic interactions occur in tetracopper(II) complex 3. In contrast, antiferromagnetic interaction is present in dicopper(II) complex 4.