Computational Study on the Dynamics of a Bis(benzoxazole)-Based Overcrowded Alkene

Understanding and
controlling molecular motions is of
pivotal importance
for designing molecular machinery and functional molecular systems,
capable of performing complex tasks. Herein, we report a comprehensive
theoretical study to elucidate the dynamic behavior of a bis(benzoxazole)-based
overcrowded alkene displaying several coupled and uncoupled molecular
motions. The benzoxazole moieties give rise to 4 different stable
conformers that interconvert through single-bond rotations. By performing
excited- and ground-state molecular dynamics simulations, DFT calculations,
and NMR studies, we found that the photochemical E-Z isomerization of the central double bond of each stable conformer
is directional and leads to a mixture of metastable isomers. This
transformation is analogous to the classical Feringa-type molecular
motors, with the notable difference that, during the photochemical
isomerization and the subsequent thermal helix inversion (THI) steps,
multiple possible pathways take place that involve single-bond rotations
that can be both coupled and uncoupled to the rotation of the naphthyl
half of the molecule.