From eilatin to isoeilatin: a skeletal rearrangement strongly influences pi-stacking of Ru(II) complex

The C(1)-symmetrical complex [Ru(bpy)(2)(ieil)][PF(6)](2) exhibits unique electrochemical and photophysical properties, and forms discrete dimers in solution and in the solid state held by weak pi-pi stacking interactions via its isoeilatin ligand, preferentially from one of its faces and in a specific orientation.     

Crystal Structures of Aripiprazole, a New Anti-psychotic Drug, and of its Inclusion Compounds with Methanol, Ethanol and Water

Aripiprazole, 7-[4-[4-(2,3-dichlorophenyl)-1-piperazinyl]butoxy]-3,4-dihydrocarbostyril, is an important new neuroleptic drug used in the treatment of schizophrenia and related psychoses. This study elucidates its detailed molecular structure and two preferred conformational forms, and relates to the solvates of this compound when crystallized from different environments. The latter is associated with the hydrogen-bonding capacity of aripiprazole through the piperazinyl and dihydrocarbostyril functions. Four unique crystal forms of this compound have been characterized using X-ray single crystal determinations, including an anhydrous structure (1), methanol (2) and hemi-ethanol (3) solvates and a hydrate (4). They were found to consist of hydrogen bonded dimers of the aripiprazole moieties that involve the cyclic (–NH–CO–)₂ di-amide interaction synthon in 1–3 (with the solvent molecules attached to them in 2 and 3), or of hydrogen bonded polymeric aggregates sustained by extended multiple bonding through water bridges in 4. These modes of supramolecular association involve two different conformers with similar energy of the drug moiety.     

Diffusion NMR spectroscopy in supramolecular and combinatorial chemistry: an old parameter--new insights

Intermolecular interactions in solution play an important role in molecular recognition, which lies at the heart of supramolecular and combinatorial chemistry. Diffusion NMR spectroscopy gives information over such interactions and has become the method of choice for simultaneously measuring diffusion coefficients of multicomponent systems. The diffusion coefficient reflects the effective size and shape of a molecular species. Applications of this technique include the estimation of association constants and mapping the intermolecular interactions in multicomponent systems as well as investigating aggregation, ion pairing, encapsulation, and the size and structure of labile systems. Diffusion NMR spectroscopy can also be used to virtually separate mixtures and screen for specific ligands of different receptors, and may assist in finding lead compounds.     

Single-site catalysis by bimetallic zinc calixarene inclusion complexes

[reaction: see text] Bimetallic alkylzinc calixarene inclusion complexes were prepared and used in the ring-opening polymerization of L-lactide. Polymers with high molecular weight and a low degree of polydispersity were obtained. 1H NMR and diffusion NMR experiments suggest that a single-site mechanism is operative.