In this perspective we will discuss recent results on structural aspects of peroxocomplexes of transition metals having the d⁰ configuration (V(V), Mo(VI), W(VI)), and show how these may be related to the reactivity of these species in both chemical and biological systems. In addition, we will consider the relevance of structural properties to their involvement as important intermediates in industrial and enzymatic catalysis. These will be related to the behaviour of peroxocomplexes of other diamagnetic transition metals, such as those with d⁸ (Pd(II), Pt(II)) configurations.

The luminescence of cerium(III) has been studied in aqueous solutions in the presence of acetate ion. In contrast to previous reports that cerium(III) carboxylate complexes do not luminesce, a weak emission is observed, which has a similar spectrum to the aquo cerium(III) species but a much shorter lifetime. Results from a variety of studies on complexation of various trivalent lanthanide ions with carboxylates, including NMR spectral and relaxation measurements, molecular mechanics calculations, deuterium isotope effects on Tb(III) luminescence lifetimes, together with literature data strongly suggest that the dominant mode of complexation between carboxylates and trivalent lanthanides involves a weak, predominantly bidentate, binding to the metal cation. We suggest that the observed emission arises from a 1 : 1 cerium acetate species involving such bidentate coordination.