A Schiff base expanded porphyrin macrocycle that acts as a versatile binucleating ligand for late first-row transition metals.

The coordination chemistry of the Schiff base polypyrrolic octaaza macrocycle 1 toward late first-row transition metals was investigated. Binuclear complexes with the divalent cations Ni(II), Cu(II), and Zn(II) and with the monovalent cation Cu(I) were prepared and characterized. Air oxidation of the Cu(I) ions in the latter complex to their divalent oxidation state resulted in a change in the coordination mode relative to the macrocycle.

Calix[4]pyrrole Schiff base macrocycles: novel binucleating ligands for Cu(I) and Cu(II).

New bimetallic copper(I) and copper(II) complexes of dipyrromethane-derived Schiff base macrocycles are reported. Two different structural motifs were identified, providing support for the notion that ligands of this type can support a variety of coordination modes. In the case of the Cu(I) complexes, the metal centers were found to have a distorted tetrahedral geometry and be coordinated to two imine nitrogens on each side of the ligand, with the exact structure depending on the choice of Schiff base macrocycle. In contrast to what is seen for Cu(I), with Cu(II) as the coordinated cation the Cu(II) metal centers assumed distorted square planar geometries, and both pyrrole N-Cu and imine N-Cu interactions were confirmed by single-crystal X-ray diffraction analysis. This structural analysis revealed a copper-copper distance of 3.47 A, while SQUID magnetic susceptibility data provided evidence for antiferromagnetic coupling between the two metal centers.

Quantum growth of magnetic nanoplatelets of Co on Si with high blocking temperature.

Self-organized Co nanoplatelets with a singular height, quantized lateral sizes, and unique shape and orientation have been fabricated on a template consisting of ordered Al nanocluster arrays on Si(111)-7 x 7 surfaces. Despite their small volume (a few nm(3)), these nanomagnets exhibit an unusually high blocking temperature (>100 K). The perpendicular direction for easy magnetization, the high blocking temperature, the size tunability, and the epitaxial growth on Si substrates make these nanomagnets important for applications in information technology.