New crown ether ligands of the Schiff base type (4a-d) were synthesized by the reaction of 2-hydroxybenzaldehyde, 3-hydroxybenzaldehyde, 4-hydroxybenzaldehyde and 2-hydroxy-1-naphthaldehyde with 6,7-dihydro-13H-dibenzo[e,h] [1,4]dioxonin-2,11-diamine (3). The structures of ligands were investigated by elemental analysis as well as IR, UV-visible, 1 H-NMR, 13 C-NMR and MS spectroscopic data. The antimicrobial and anti-yeast activities of the ligands were screened in vitro against the organisms Escherichia