Spectroscopic and conductometric studies of molecular complex formation between 2,4,6-trinitrophenol and diaza-18-crown-6, tetraaza-14-crown-4 and cryptand C222 in 1,2-dichloroethane solution

The formation of molecular complexes between 2,4,6-trinitrophenol (TNP) and aza-substituted macrocycles diaza-18-crown-6 (DA18C6), tetraaza-14-crown-4 (TA14C4) and cryptand C222 in 1,2-dichloroethane solution was investigated spectrophotometrically and conductometrically. The mole ratio and continuous variations studies based on both physicochernical techniques employed clearly revealed the formation of both 1:1 and 2:1 (TNP:macrocycle) adducts in solution. Formation of the resulting complexes was also confirmed by H-1 NMR and IR spectroscopic studies. Formation constants of the resulting complexes were evaluated from computer fitting of the corresponding mole ratio data. Stability of the resulting complexes was found to vary in the order C222 approximate to TA14C4 > DA18C6. (c) 2005 Elsevier B.V. All rights reserved.