Persistent Solid-State Bipyridine Atropisomerism in a Ferrocenyl-Functionalized Chiral BINOL Scaffold.

In this work, we report the synthesis and structural characterization of a novel organometallic bipyridine-based atropisomer featuring two (S)-BINOL-derived units, each functionalized with a ferrocene moiety and linked by a 4,4'-disubstituted 2,2'-bipyridine bridge. Although the molecule appears symmetric, single-crystal X-ray diffraction establishes its axial chirality, as demonstrated by Flack x = -0.020(14) and Hooft x = 0.013(18) parameters. The bipyridine core, sterically hindered by the bulky ferrocenyl groups, imposes a rigid atropisomeric structure. To better understand this behavior, a new Cu-(II) complex is presented to examine how peripheral substitution affects the accessibility and coordination capacity of the bipyridine core; these factors ultimately dictate the solid-state atropisomerism and rigidity of the resulting multinuclear architecture.