The Synthesis of Some New Mono and bis(Crown Ether)s and Their Sodium Complexes. Tautomerism in o‐Hydroxybenzo‐15‐crown‐5 Schiff Bases as Studied by UV‐VIS Spectrophotometry

Abstract New mono‐ and bis(crown ether) ligands have been synthesized by the condensation of the appropriate formylbenzo‐15‐crown‐5 [(2) and (4)] with ethanolamine and 1,2‐bis[(4‐aminophenoxy)methyl]benzene (6), respectively. The diamine (6), was prepared by the reaction of 1,2‐bis(bromomethyl)benzene and p‐nitrophenol in the presence of NaOH forming the dinitro compound (5) which is subsequently reduced to compound (6) using hydrazine hydrate and Pd/C. Homonuclear sodium complexes of the mono‐ and bis(crown ether) ligands have been prepared with sodium perchlorate. The UV‐VIS spectra of o‐hydroxycrown ether Schiff bases (7), (8), (7a), and (8a) have been studied in various solvents. The results indicate that bands observed at higher values than 400 nm to be the result of the keto‐amine form of the ligands and complexes. All of the crown ether ligands and their complexes have been characterized by elemental analyses, IR, UV, and NMR spectra.