Formation of complexes between aza derivatives of crown ethers and primary alkylammonium salts. Part 4. Diaza-18-crown-6 derivatives
Abstract
Diaza analogues of 18-crown-6 (7b) and (10b), benzo-18-crown-6 (8b), and dibenzo-18-crown-6 (9b) form strong complexes in methylene chloride with primary alkylammonium thiocyanates. The n.m.r. spectra of these complexes show temperature dependence which can be explained in the terms of different types of guest exchange processes. The complexes of the dibenzo-18-crown-6 analogue (9b) appear to exist in one form only but the spectra of the complexes of the other 18-crown-6 analogues (7b), (8b), and (10b) indicate that two or more different types of complex are in equilibrium. The possible nature of these closely related but different species is discussed.