Synthesis and characterization of original calix–salen type ligands

Polycondensation reactions between various modified disalicylaldehyde derivatives and two chiral diamines afforded in each case macrocyclic structures, named calix–salen. Mixtures of oligomers (dimers to pentamers) were qualitatively analyzed by Maldi-Tof and 1H NMR DOSY experiments allowed their easy quantitative investigation. Tuning the reaction conditions and namely the concentration of both monomeric partners led interestingly to the selective preparation of the dimer or the tetramer as main products, in diluted or concentrated media, respectively.