1,1'-Binaphthyl-substituted diphosphene: synthesis, structures, and chiral optical properties

Helitwistacenes-Combining Lateral and Longitudinal Helicity Results in Solvent-Induced Inversion of Circularly Polarized Light

Helicity is expressed differently in ortho- and para-fused acenes-helicenes and twistacenes, respectively. While the extent of helicity is constant in helicenes, it can be tuned in twistacenes, and the handedness of flexible twistacenes is often determined by more rigid helicenes. Here, we combine helicenes with rigid twistacenes consisting of a tunable degree of twisting, forming helitwistacenes. While the X-ray structures reveal that the connection does not affect the helicity of each moiety, their electronic circular dichroism (ECD) and circularly polarized luminescence (CPL) spectra are strongly affected by the helicity of the twistacene unit, resulting in solvent-induced sign inversion. ROESY NMR and TD-DFT calculations support this observation, which is explained by differences in the relative orientation of the helicene and twistacene moieties.

Palladium(II) complexes of bis(diphosphene) with different coordination behaviors

Organophosphorus compounds possessing a P-P double-bond character are intriguing materials in coordination chemistry because it is possible to form a variety of coordination modes from the π-bond in addition to the lone pairs. We report herein the complexation of a new bidentate ligand, ethylene-tethered bis(binaphthyldiphosphene) (S,S)-2, with palladium(II) species. The reaction of (S,S)-2 with [Pd(π-allyl)(cod)](SbF₆) and PdCl₂(cod) afforded η¹/η¹-bis(diphosphene) complex 7 and η¹-diphosphene/η²-phosphanylphosphide complex 8, respectively. The latter was characterized by a chloride migration from the palladium atom to a phosphorus atom due to the high electron-accepting character of the PP moiety. Theoretical calculations revealed the migration process and nature of complex 8.