Reduzierte Cobalt-meso-tetraphenylporphyrin-Komplexe: Synthese und Struktur von [Na(thf)3]2[Co(TPP)]

Inhibition of Alkali Metal Reduction of 1-Adamantanol by London Dispersion Effects

A series of alkali metal 1-adamantoxide (OAd¹ ) complexes of formula [M(OAd¹ )(HOAd¹ )₂ ], where M=Li, Na or K, were synthesised by reduction of 1-adamantanol with excess of the alkali metal. The syntheses indicated that only one out of every three HOAd¹ molecules was reduced. An X-ray diffraction study of the sodium derivative shows that the complex features two unreduced HOAd¹ donors as well as the reduced alkoxide (OAd¹ ), with the Ad¹ fragments clustered together on the same side of the NaO₃ plane, contrary to steric considerations. This is the first example of an alkali metal reduction of an alcohol that is inhibited from completion due to the formation of the [M(OAd¹ )(HOAd¹ )₂ ] complexes, stabilized by London dispersion effects. NMR spectroscopic studies revealed similar structures for the lithium and potassium derivatives. Computational analyses indicate that decisive London dispersion effects in the molecular structure are a consequence of the many C-H⋅⋅⋅H-C interactions between the OAd¹ groups.

HgII -Mediated TlI -to-TlIII Oxidation in Dynamic PbII /Tl Porphyrin Complexes

Compared with their purely organic counterparts, molecular switches that are based on metal ion translocations have been underexplored, and more particularly, it remains challenging to control the translocation of several particles in multisite receptors. Recently, bimetallic complexes that undergo double translocation processes have been developed with bis-strapped porphyrin ligands. To implement a redox control for these systems, we have investigated the formation of heterobimetallic lead/thallium complexes, with thallium in the +I and +III oxidation states. Two different complexes were characterized: 1) a Pb^II /Tl^I complex, in which both metal ions interact with the N-core on its different sides, and 2) a Pb^II /Tl^III complex with Tl^III selectively bound to the N-core and Pb^II selectively bound to the strap opposite to Tl^III . These two complexes undergo interconversion between their two degenerate forms (same coordination of the metal ions but on opposite sides) by different intra or intermolecular translocation pathways. In addition, conversion of the Pb^II /Tl^I complex into its Pb^II /Tl^III counterpart was achieved by addition of a stoichiometric amount of Hg^II salt as a sacrificial electron acceptor. These results further contribute to the elaboration of devices that feature redox-controlled compartmentalized double translocations.