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Information on the molecular distribution and ageing trend of brain iron in post-mortem material from normal subjects is scarce. Because it is known that neuromelanin and ferritin form stable complexes with iron(III), in this study we measured the concentration of iron, ferritin and neuromelanin in substantia nigra from normal subjects, aged between 1 and 90 years, dissected post mortem. Iron levels in substantia nigra were 20 ng/mg in the ®rst year of life, had increased to 200 ng/mg by the fourth decade and remained stable until 90 years of age. The H-ferritin concentration was also very low (29 ng/mg) during the ®rst year of life but increased rapidly to values of < 200 ng/mg at 20 years of age, which then remained constant until the eighth decade of life. L-Ferritin also showed an increasing trend during life although the concentrations were < 50% less than that of H-ferritin at each age point. Neuromelanin was not detectable during the ®rst year, increased to < 1000 ng/mg in the second decade and then increased continuously to 3500 ng/mg in the 80th year. A Mo È ssbauer study revealed that the high-spin trivalent iron is probably arranged in a ferritin-like iron2oxyhydroxide cluster form in the substantia nigra. Based on this data and on the low H-and L-ferritin content in neurones it is concluded that neuromelanin is the major iron storage in substantia nigra neurones in normal individuals.

Pythagorean harmony can be found in the spherical polyoxometalate clusters described here (see illustration for an example of a structure), since there are interesting relationships between the so-called magic numbers (12, 32, 42, 72, 132) relevant for spherical viruses and the number of the building blocks in the cluster. The size of these Keplerate clusters can be tailored by varying the type of connections between the pentagons by means of different spacers.

Dtw'ilctrtecl to Piofcrc.or Eimt Otto F i~t h e r 017 the> ol c ci\ioi? of h r~ 75th birt~7da1The coordination chemistry of metals in unusual oxidation states is a fascinating aspect of research in the field ofmetalloporphyrins. Of particular significance in this respect are oxoiron porphyrins containing tetravalent iron, since complexes of this sort occur as reactive intermediates in numerous biological and biomimetic oxidation processes."] Iron(iv) porphyrins, in which the metal is not present as part of a [Fe=O] (FRG) phyrinoids corrole["-the aromatic parent substance of corrin. the ring system of vitamin B,, --and iso~orrole['~ may enable the preparation of the corresponding neutral complexes, that is. types 2 and 4, respectively. This supposition appeared to be substantiated all the more so. as it was recently shown that stable iron(iv) complexes with ligands based on pentane-2,4-dione-bis(S-alky1isothiosemicarbazides)-which are also trianionic-could be synthesized.18,9] We have now found that octaethylcorrole 5 can be readily converted into the triad of stable complexes 7-9, all of which contain formally tetravalent iron."'] Furthermore, the existence of the iron corrole 10 (bearing an axial pyridine ligand) with a formal oxidation state of the metal of + 111 was corroborated.