A molecular machine directs the synthesis of a catenane

Precise mechanical manipulation of molecules is inherently difficult due
to random thermal motion. While directed movement on the molecular scale
has been achieved, using it to impose specific, especially energetically
disfavored, shapes on molecules and construct mechanically interlocked
structures remains a fundamental challenge. Here, we report the synthesis
of a catenane enabled by a molecular motor that winds molecular strands
into discrete entangled structures, each defined by a specific number of
mechanical crossings. Light energy drives unidirectional motor rotation,
enabling path-dependent control over a sequence of thermodynamically
disfavored yet mechanically distinct and kinetically stable winding
states, which are covalently captured and subsequently released to yield a
catenane. This machine-directed approach offers a general proof-of-concept
strategy for the template-free construction of mechanically interlocked
molecules.