Synthesis of 1, 3-Alternate calic [4]-cyclen-benzo-crown-6 and its complexation with metal cations and organic molecules

Abstract

A new derivative of 1,3-alternate calix[4]arene, 1,3-alternate calix[4]-cyclen-benzo-crown-6 (20) containing a cyclen subunit on one site and benzo crown-6 on the other side has been synthesized. The complexation studies of the synthesized ligand were carried out by mean of 1H-NMR spectroscopy. With picrate salts, ligand 20 formed 1:1 complex with Cs+ which resided in benzo crown ether loop. For a 1:1 complex of potassium and zinc picrates, 1H-NMR spectra of these complexes shown that potassium and zinc ions were encapsulated in the cyclen unit of 20. An influence of anions (as a counter ion) towards zinc complexes was studies. From 1H-NMR spectra, it was found that interaction between zinc salts and ligand 20 depended on the shape, size and binding ability of counter ions and the interaction degrees were in order of SO4 2- >AcO - >NO3 -. Moreover, two types of complexes, 2:1 and 1:1 complexes, were observed in the case of ZnSO4. Its complexation behavior of 20*ZnSO4 was confirmed by 1H-NMR titration. In zinc halides series, the interaction between zinc halides and ligand 20 were in the order of 20*ZnCl2<20*ZnBr2<20*ZnI2. Due to the synthesized compound possesses NH groups at the cyclen unit, the complexation studies of this ligand with organic molecules were investigated. 1H-NMR spectra, demonstrated the interaction between host 20 and guest molecules by means of hydrogen-bonding due to the migration of CH2 signals of cyclen unit and the neighboring phenyl unit. It was also revealed that ligand 20 possessed a higher affinity towards disubstituted benzenes than monosubstituted ones.