Synthesis and Study of some Crown Ether Complexes of Ba(II) Ion by IR and 1H-NMR Analysis

The affinity of crown ether for an alkali and alkaline earth metal ion is dependent on the size of the ring of the crown ether with some exceptions. The crown ether-metal ion binding is enhanced in the absence of non-coplanar donor oxygen atoms and electron withdrawing substituents in the crown ether skeleton. The study of absorption of radio frequency radiation by a magnetic nucleus (I¹0), in the presence of applied magnetic field provides useful information regarding structure of a number of organic and inorganic compounds. The present paper describes preparation and characterization of some Ba(II) complexes with 1,4,7,10,13,-pentaoxacyclopentadecane (15C5), 1,4,7,10,13,16,- hexaoxacyclooctadecane (18C6) and 2,3,11,12-dibenzo-1,4,7,10,13,16,-hexaoxacyclooctadeca-2,11-diene (dibenzo18C6), having five and six donar oxygen atoms respectively. Small but noticeable changes were observed in the chemical shift of 1-H in 15C5, 18C6 and, 1-H as well as 2-H, in dibenzo18C6, which moved downfield upon complexation with barium ion. The metal salts used for complexation are salts of nitrophenols. Products were isolated from barium salts of all the three monoionic ligands, 2-nitrophenol (ONPH), 2,4-dinitrophenol (DNPH), 2,4,6- trinitrophenol (TNPH) and 8-hydroxyquinoline (8HQH). The bonding pattern and structure of complexes were suggested from the studies of elemental analysis, molar conductivity, IR, UV-Vis and 1H-NMR spectral analysis.