Synthesis, structural characterization and extraction studies of 17-, 18-, 19- and 20- membered N2O2-donor macrocyclic Schiff bases

Two new macrocyclic Schiff bases m 3 and m 4 (m 3 = 1,5-diaza-2,4:7,8:17,18-tribenzo-9,16-dioxa-cyclononadeca-1,5-dien; m 4 = 1,5-diaza-2,4:7,8:18,19- tribenzo-9,17-dioxa-cycloeicosa-1,5-dien) were synthesized by reactions of the appropriate dialdehyde and diamine. The compounds were characterized by means of FT-IR and NMR spectroscopy, TG/DSC and elemental analysis. The crystal and molecular structures were determined by the single crystal X-ray diffraction method. Both molecules are N2O2-donor macrocyclic Schiff bases with 19 and 20 atoms in their inner macrocyclic rings and of a similar molecular structure. A different crystal packing arrangement of the molecules is caused by the differences in macrocycle planarity. The extraction experiments of the aforementioned compounds were performed by using metallic picrate salts, and simultaneously for the previously synthesized 17- and 18- membered macrocyclic analogues (m 2 and m 1). The metal cation extractability was determined for m 1, m 2, m 3 and m 4 by UV–Vis spectrophotometry in order to find correlation of structural features and the extraction capabilities of the Schiff bases. The highest metal cation extraction percentage was determined for the Hg2+ ion in the case of the m 2 macrocycle.