Brigitte Nohra

Heterometallic 3d–4f cubane clusters inserted in polyoxometalate matrices

Unprecedented molecular and bidimensional compounds based on monovacant polyoxometalates capped by heterometallic 3d-4f {LnCu(3)(OH)(3)O} (Ln = La, Gd, Eu) cubane fragments have been characterized and their magnetic properties investigated.

Lanthanide Polyoxocationic Complexes: Experimental and Theoretical Stability Studies and Lewis Acid Catalysis

The [ε-PMo(V)(8)Mo(VI)(4)O(36)(OH)(4){Ln(III)(H(2)O)}(4)](5+) (Ln=La, Ce, Nd, Sm) polyoxocations, called εLn(4), have been synthesized at room temperature as chloride salts soluble in water, MeOH, EtOH, and DMF. Rare-earth metals can be exchanged, and (31)P NMR spectroscopic studies have allowed a comparison of the affinity of the reduced {ε-PMo(12)} core, thus showing that the La(III) ions have the highest affinity and that rare earths heavier than Eu(III) do not react with the ε-Keggin polyoxometalate. DFT calculations provide a deeper insight into the geometries of the systems studied, thereby giving more accurate information on those compounds that suffer from disorder in crystalline form. It has also been confirmed by the hypothetical La→Gd substitution reaction energy that Ln ions beyond Eu cannot compete with La in coordinating the surface of the ε-Keggin molybdate. Two of these clusters (Ln=La, Ce) have been tested to evidence that such systems are representative of a new efficient Lewis acid catalyst family. This is the first time that the catalytic activity of polyoxocations has been evaluated.

Coordination-Driven Hierarchical Organization of π-Conjugated Systems: From Molecular to Supramolecular π-Stacked Assemblies

The reaction of U-shaped, bimetallic, Cu(I) complexes, assembled from a heteroditopic pincer, with cyano-capped pi-conjugated linkers gives a straightforward access to pi-stacked metallocyclophanes in good yields. In these assemblies, the pi-walls have an almost face-to-face arrangement. The versatility of this rational supramolecular synthesis is demonstrated with the use of linkers that have nanoscale lengths (up to 27.7 A), different chemical compositions (oligo(para-phenylenevinylene)s OPVs, oligo(phenylene)s, oligo(phenylethynylene)s), and alternative geometries (linear, angular). Linkers that incorporate an internal pyridyne moiety can also be employed. X-ray diffraction studies revealed that the metallocyclophanes based on linear linkers self-organize into infinite pi-stacked columns in the solid state with intermolecular distances of about 3.6 A. This approach, based on coordination-driven self-assembly, provides a novel and rational strategy for the stacking of extended pi-systems in the solid state.

Assembly of Helicene‐Capped N,P,N,P,N‐Helicands within CuI Helicates: Impacting Chiroptical Properties by Ligand–Ligand Charge Transfer

Helicat- und Helicenchemie treffen sich, wenn funfzahnige Phosphol-Pyridin-Helicanden an CuI- oder AgI-Zentren koordinieren. Bei diesem Prozess entstehen konfigurationsstabile Doppelstranghelicate mit verbruckenden Phosphanen in mehreren Koordinationsmodi. Mit enantiomerenreinen Helicenen versehene Helicanden ergaben enantiomerenreine Helicate.

Organophosphorus-Conjugated Materials for Optoelectronic Applications

The supramolecular organization of nano-size π -conjugated systems within metalloparacyclophanes and coordination polymers synthesis is described.