Abstract Previous studies of macrocycles having alkyl sidearms terminated in adenine or thymine have been focused on intermolecular association. Electrospray mass spectrometric analyses suggested that sodium complexation could be a major alternative process in the presence of the appropriate cation. Sodium cation complexation by N, N′-bis (3-(1- thyminyl) propyl)-4, 13-diaza-18-crown-6 has been confirmed by X-ray crystallographic ...