A STUDY OF THE COMPLEXATION OF BIS(M-PHENYLENE) CROWN-ETHERS AND SECONDARY AMMONIUM-IONS

Two macrocycles, bis(m-phenylene)-26-crown-8 (1) and bis(m-phenylene)- 32-crown-10 (2), were combined with several linear components, dibenzy l- (3 . PF6), di-n-butyl- (4 . PF6), and diphenethyl-(5 . PF6) ammoniu m hexafluorophosphate salts. The smaller macrocycle 1 was shown not to complex effectively with any of the ammonium salts in solution by H-1 NMR, but 1:1 complexes were shown to exist in the ''gas phase'' as [1 :3], [1:4], and [1:5] by high-resolution fast atom bombardment mass sp ectrometry (HRFABMS) and electrospray ionization mass spectrometry (ES IMS). The X-ray crystal structure of macrocycle 1 is reported. The lar ger macrocycle 2 did form 1:2 complexes with the ammonium salts in sol ution, which were observed as well in the solid and gas phases. X-ray crystal structures of the pseudorotaxanes [2:(3)(2)]. 2PF(6) and [2:(5 )(2)]. 2PF(6) were determined and are discussed. The pseudorotaxanes a re stabilized by hydrogen bonding between the ammonium hydrogens of th e linear salt unit and the oxygens of the crown ether macrocycle. Seco ndary stabilization also occurs by edge-to-face pi stacking.