The type 1 copper site of pseudoazurin: axial and rhombic.

We report on a high-frequency electron-paramagnetic-resonance study of the type 1 copper site of pseudoazurin. The spectra fully resolve the contribution of a nearly axial spectrum besides the rhombic spectrum, which unequivocally proves the existence of two conformations of the copper site. Pseudoazurins have been considered from Achromobacter cycloclastes including eight mutants and from Alcaligenes faecalis.

Characterization of one-electron oxidized copper(II)-salophen-type complexes; effects of electronic and geometrical structures on reactivities.

One-electron oxidized salophen-type complexes, [Cu(salophen)](+) (H2salophen = N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminobenzene), and its methoxy derivatives, [Cu(MeO-salophen)](+) and [Cu(salophen-(MeO)2)](+) (H2MeO-salophen = N,N'-bis(3-tert-butyl-5-methoxysalicylidene)-1,2-diaminobenzene, H2salophen-(MeO)2 = N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-diamino-4,5-dimethoxybenzene), have been synthesized and structurally characterized, and their reactivities have been investigated. The solid state structures of the one-electron oxidized forms of these complexes suggested that [Cu(salophen)](+) and [Cu(MeO-salophen)](+) can be assigned to relatively localized Cu(ii)-phenoxyl radical complexes, while [Cu(salophen-(MeO)2)](+) is the diiminobenzene radical complex. On the other hand, [Cu(salophen)](+) in solution showed a different electronic structure from that of the solid sample, the radical electron being delocalized over the whole π-conjugated ligand.