Tetra- and Di-Nuclear Copper(II) Complexes with Stereoisomers of Sulfinylcalix[4]arene Arising from the Disposition of Four S=O Groups

Abstract

Abstract A systematic investigation was conducted on the structures of tetra- and di-nuclear copper(II) complexes with three stereoisomers of sulfinylcalix[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=O orientation (H4Lrtct) reacted with Cu(OAc)2 to form [CuII4(Lrtct)(OAc)3(μ-MeO)(MeOH)] (1), in which Lrtct4− adopts a cone conformation to afford tetrakis fac-tridentate coordination through four phenoxo oxygens and four sulfinyl groups giving a square CuII4 core. Ligands H4Lrccc and H4Lrctt having cis–cis–cis and cis–trans–trans configurations formed [CuII4(Lrccc)(OAc)3(μ-OH)] (2) and [CuII4(Lrctt)(OAc)3(μ-OH)] (3), respectively, which have common features, such as a cone-type conformation of L4−, tetrakis fac-tridentate coordination fashion, and tetracopper(II) core in a square-pyramidal geometry. The similarities among 1–3 clearly show that sulfinylcalix[4]arenes can coordinate to CuII 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)2] as a copper(II) source, H4Lrctt formed [CuII2(H2Lrctt)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.