Synthesis of Core-Modified Third-Generation Light-Driven Molecular Motors

The synthesis and characterization
of a series of light-driven
third-generation molecular motors featuring various structural modifications
at the central aromatic core are presented. We explore a number of
substitution patterns, such as 1,2-dimethoxybenzene, naphthyl, 1,2-dichlorobenzene,
1,1′:2′,1″-terphenyl, 4,4″-dimethoxy-1,1’:2′,1″-terphenyl,
and 1,2-dicarbomethoxybenzene, considered essential for designing
future responsive systems. In many cases, the synthetic routes for
both synthetic intermediates and motors reported here are modular,
allowing for their post-functionalization. The structural modifications
introduced in the core of the motors result in improved solubility
and a bathochromic shift of the absorption maxima. These features,
in combination with a structural design that presents remote functionalization
of the stator with respect to the fluorene rotors, make these novel
motors particularly promising as light-responsive actuators in covalent
and supramolecular materials.