Anion- and Solvent-Induced Rotary Dynamics and Sensing in a Perylene Diimide [3]Catenane

A novel dynamic [3]­catenane
consisting of a large four-station
central macrocycle which incorporates a bay tetrachloro-functionalized
perylene diimide (PDI) unit and two triazolium anion-binding motifs,
mechanically bonded with two smaller isophthalamide-containing macrocycles,
is constructed using an anion template synthetic methodology. Proton
NMR, electronic absorption, and fluorescence emission spectroscopies
together with molecular dynamics simulations are used to investigate
the anion recognition- and solvent-dependent dynamic properties of
the higher-order mechanically interlocked molecule. Importantly, unprecedented
solvent-dependent and anion-binding-induced circum­rotatory motion
in a hetero[3]­catenane system is demonstrated where the exotic dual
rotary switching behavior provides a unique and sophisticated mechanism
for optical anion sensing in competitive protic organic and aqueous–organic
media.