A Rotation-Inversion Dual-Motion Molecular Switch: Race for NMR Signaling

The interplay between the thermal
helical inversion (THI) of the stiff-stilbene moiety
and the rotation of the dimethylamino
(DMA) group in 1 results in a dependence of the DMA NMR
signals on the THI kinetics in (E)-1 but the rotation kinetics in (Z)-1, because the faster motion mode is responsible. Consequently, the
photochemical switching from (E)-1 to
(Z)-1 illustrates the phenomenon of
“switchable motion detection” by the same set of NMR
signals in a dual-motion molecular system.