New zircon and apatite fission-track ages obtained on samples from all lithotectonic units exposed on Naxos Island are presented. Zircon ages of the exhumed metamorphic rocks range from 25.2 to 9.3 Ma and from 13.0 to 6.4 Ma for apatite. Zircon track-length analysis distinguishes partial overprinting of an earlier event (M1) in the south. Northwards no overprint is seen and the ages there represent rapid exhumation since c. 12 Ma. Both zircon and apatite ages are slightly older toward the north of the island probably due to variation of the geotherm in the proximity of the fault.Zircon fission-track ages of the granodiorite range from 13.7 to 12.2 Ma are statistically identical to previously determined U–Pb ages. Apatite fission-track ages however, yield a younging trend from south to north from 12.9 to 9.0 Ma. This could be due to differential depth of emplacement and/or to differential exhumation during tectonic unroofing by a top-to-the north detachment.Fission-track ages on detrital grains in Lower Miocene sediments indicate a source not identified within the present outcropping rocks of Naxos. Ages on boulders and grains in the Middle to Upper Miocene sediments point to rapid erosion until about 8.5–7 Ma.

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Dendritic iron porphyrins were synthesized as functional mimics of globular electron-transfer heme proteins.The cascade molecules 1 * Zn-3 -Zn of first to third generation were obtained starting from the (meso-diarylporphyrin) zinc 6 * Zn which contains four carboxylate arms for attachment of the poly(ether-amide) dendritic branches by peptide-coupling methodology (Scheme I). Generation 3 compound 3 . Zn with 108 methyl-carboxylate end groups has a molecular weight of 19054 D, and computer modeling suggests that its structure is globular and densely-packed, measuring ea. 4 nm in diameter and, therefore, similar in dimensions to the electron-transfer protein cytochrome-c. Starting from the generation 1 poly(carboxy1ic acid) 11 * Zn and the generation 2 analog 12 * Zn the dendritic Zn" porphyrins 4 * Zn and 5 . Zn, respectively, were obtained by esterification with triethyleneglycol monomethyl ether (Schemes 3 and 4). Demetallation followed by insertion of Fe" and in situ oxidation afforded the water-soluble dendritic iron porphyrins 4 * FeCl and 5 * FeCl. The electrochemical behavior of esters 1 * Zn -3 . Zn in organic solvents changed smoothly with increasing dendritic generation (Table f).Progressing from 1 * Zn to 3 . Zn in THF, the first porphyrin-centered oxidation and reduction potentials become more negative by 320 and 210 mV, respectively. These changes were attributed to strong microenvironmental effects imposed on the electroactive core by the densely packed dendritic surroundings. The electrochemical properties of 4 * FeCI and 5 -FeCl were investigated by cyclic voltammetry in both CH,CI, and H,O (Tables 2 and 3). Progressing from 4 . FeCl to 5 * FeCl in CH,CI,, the redox potential of the biologically relevant Fe"'/Fe" couple remained virtually unchanged, whereas in aqueous solution, 5 * FeCl exhibited a potential 420 mV more positive than did 4 . FeCI. The large difference between these potentials in H,O was attributed to differences in solvation of the core electrophore. Whereas the relatively open dendritic branches in 4 -FeCl do not impede access of bulk solvent to the central core, the densely packed dendritic superstructure of 5 * FeCl significantly reduces contact between the heme and external solvent. As a result, the more charged Fe"' state is destabilized relative to Fe", and the redox potential is strongly shifted to a more positive value.

Two types of dendritically functionalized iron(II) porphyrins were prepared (Scheme) and investigated in the presence of 1,2-dimethylimidazole (1,2-DiMeIm) as the axial ligand as model systems for T(tense)-state hemoglobin (Hb) and myoglobin (Mb). Equilibrium O 2 -and CO-binding studies were performed in toluene and aqueous phosphate buffer (pH 7). UV/VIS Titrations (Fig. 4) revealed that the two dendritic receptors 1 ¥ Fe II -1,2-DiMeIm and 2 ¥ Fe II -1,2-DiMeIm ( Fig. 2) with secondary amide moieties in the dendritic branching undergo reversible complexation ( Fig. 5) with O 2 and CO in dry toluene. Whereas the CO affinity is similar to that measured for the natural receptors, the O 2 affinity is greatly enhanced and exceeds that of T-state Hb by a factor of ca. 1500 (Table). The oxygenated complexes possess half-lives of several h (Fig. 6). This remarkable stability originates from both dendritic encapsulation of the iron(II) porphyrin and formation of a H-bond between bound O 2 and a dendritic amide NH moiety (Fig. 11). Whereas reversible CO binding was also observed in aqueous solution (Fig. 10), the oxygenated iron(II) complexes are destabilized by the presence of H 2 O with respect to oxidative decay (Fig. 9), possibly as a result of the weakening of the O 2 ¥¥¥ HÀN H-bond by the competitive solvent. The comparison between the two dendrimers with amide branchings and ester derivative 3 ¥ Fe II -1,2-DiMeIm (Fig. 2), which lacks H-bond donor centers in the periphery of the porphyrin, further supports the role of H-bonding in stabilizing the O 2 complex against irreversible oxidation. All three derivatives bind CO reversibly and with similar affinity (Fig. 8) in dry toluene, but the oxygenated complex of 3 ¥ Fe II -1,2-DiMeIm undergoes much more rapid oxidative decomposition (Fig. 7).

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