Designed asymmetric coordination helicates with bis-β-diketonate ligands.

A new bis-(β-diketone) ligand featuring built-up structural asymmetry yields non-symmetric Fe(iii) and Ga(iii) dinuclear, triple-stranded helicates by design. Their structural properties have been studied, both in solid state and in solution, and compared with their corresponding symmetric analogues. The robustness observed shows the potential of this synthetic strategy to develop non-symmetric helicoidal motifs with specific functional groups.

A Magneto-optical Molecular Device: Interplay of Spin Crossover, Luminescence, Photomagnetism, and Photochromism.

A bis(pyrazolylpyridyl) ligand, L, containing a central photochromic dithienylethene spacer predictably forms a ferrous [Fe L ] helicate exhibiting spin crossover (SCO). In solution, the compound [Fe L ](ClO ) (1) preserves the magnetic properties and is fluorescent. The structure of 1 is photo-switchable following the reversible ring closure/opening of the central dithienylethene via irradiation with UV/visible light.

Molecules Designed to Contain Two Weakly Coupled Spins with a Photoswitchable Spacer.

Controlling the charges and spins of molecules lies at the heart of spintronics. A photoswitchable molecule consisting of two independent spins separated by a photoswitchable moiety was designed in the form of new ligand H L, which features a dithienylethene photochromic unit and two lateral coordinating moieties, and yields molecules with [MM⋅⋅⋅MM] topology. Compounds [M L (py) ] (M=Cu, 1; Co, 2; Ni, 3; Zn, 4) were prepared and studied by single-crystal X-ray diffraction (SCXRD).

A Useful Allene for the Stereoselective Synthesis of Protected Quaternary 2-Amino-2-vinyl-1,3-diols.

Treatment of readily available allene 1 with CyBH followed by addition of an aldehyde led to quaternary protected 2-amino-2-vinyl-1,3-diols in high yield and excellent stereochemical purity. The choice of benzoyl as N-protecting group is critical since the observed N- to O-Bz transfer during the process prevents later undesired isomerizations in the adducts and keeps all heteroatoms protected.

Total synthesis of (-)-isoavenaciolide.

An enantioselective approach to (-)-isoavenaciolide was achieved starting from 1-undecyn-3-ol. The synthesis relied upon the preparation of a chiral 4-silyloxy-2-alkenylborane by hydroboration of a protected 2,3-allenol and subsequent stereoselective addition to 2-thiophenecarboxaldehyde.