Molecular Tweezers: Synthesis and Formation of Host-Guest Complexes

A chiral molecular tweezer obtained from (+)-usnic acid placed in solution in the presence of various aromatic compounds afforded complexes with low association constants. Thus, the X-ray structure of assembly 3i is presented, where the guest is sandwiched between the two pincers of the tweezer. The association constants for various guests were determined through different methods. Finally, other tweezers with electron-rich aromatic aldehydes and ketones were prepared from (1R,2R)-1,2-diaminocyclohexane. The most interesting complexes were also confirmed through structural analysis, and the best results were obtained with 10-hydroxyphenanthrene-9-carbaldehyde (5i) as the aromatic moiety.