Stereoisomerism of molecular multipropellers. 1. Static stereochemistry ofbis- and tris-triaryl systems

The static stereoisomerism of bis- and tris-triaryl systems has been analyz ed by a systematic stereochemical analysis, and the resulting theoretical p redictions have been experimentally confirmed by using reversed-phase HPLC and ESR and H-1 NMR spectroscopies with a family of seven distinct polychlo rinated aromatic multipropellers, To analyze the static stereochemistry of these molecules, we have developed a specific procedure that uses a symmetr y-adapted symbolic notation, allowing the theoretical prediction of both th e number and symmetry of the isomers of the investigated molecules. Due to the steric hindrance introduced by the presence of bulky chlorine substitue nts, (all) conformational isomers can be characterized experimentally by se veral independent techniques confirming the theoretical stereochemical pred ictions. The different propeller moieties that constitute the molecule appe ar to be nearly independent of each other. Consequently, most of the observ ed isomers show comparable populations in solution at room temperature.