Synthesis and reversible recognition for organic ammoniums of a molecular receptor based on calix[6]arene

Calix [ 6] arenes often serve as molecular host in supramolecular chemistry, however, they show a conformation flexibility due to the inversion of the aromatic rings. It is important to control the structure flexibility of calix [ 6] arenes. In this work, a C-3v -symmetrical molecular receptor calix [ 6] TPA was synthesized and characterized via H-1 NMR, (13) C NMR, ESI-MS, and X-ray structural. analysis. Molecular recognitions of calix [ 6] TPA for small organic ammoniums were investigated with H-1 NMR, and the inclusions of the straight chain ammoniums were reversiblly controlled by the acidity of the solution. The results indicate that the introduction of a tripodal N-4-crypto cap is beneficial to rigidify the structure in a cone conformation, the hydrophobic cavity is an efficient receptor for organic guests, and the reversible recognition of straight chain ammoniums can be potentially applied in separation of organic amines.