Homochiral [2]Catenane and Bis[2]catenane from Alleno-Acetylenic Helicates - A Highly Selective Narcissistic Self-Sorting Process

Homochiral strands of alternating
alleno-acetylenes and phenanthroline
ligands (P)-1 and (P2)-2, as well as their corresponding enantiomers,
selectively assemble with the addition of silver­(I) salt to yield
dinuclear and trinuclear double helicates, respectively. Upon increasing
the solvent polarity, the dinuclear and trinuclear helicates interlock
to form a [2]­catenane and bis[2]­catenane, bearing 14 chirality elements,
respectively. The solid-state structure of the [2]­catenane reveals
a nearly perfect fit of the interlocked strands, and the ECD spectra
show a significant amplification of the chiroptical properties upon
catenation, indicating stabilization of the helical secondary structure.
Highly selective narcissistic self-sorting was demonstrated for a
racemic mixture consisting of both short and long alleno-acetylenic
strands, highlighting their potential for the preparation of linear
catenanes of higher order.