GAS-PHASE STRUCTURE AND RELATIVE STABILITY OF PROTON-BOUND HOMO-AND HETEROCHIRAL CLUSTERS OF TETRA-AMIDE MACROCYCLES WITH AMINES

摘要

The structure,stability,and CID pattern of proton-bound homochiral and heterochiral complexes,formed in the gas phase by the combination of two molecules of a chiral macrocyclic tetra-amide and an amine B,i.e.CH3NH2,(CH3)2NH,or(S)-(-)-1-phenylethylamine,have been examined by ESI-ITMS-CID mass spectrometry.With B = CH3NH2,the CID pattern is characterized by the predominant loss of B,accompanied by a much less extensive release of one tetra-amide molecule.With(S)-(-)-1-phenylethylamine,loss of a tetra-amide molecule efficiently competes with loss of B.Finally,with(CH3)2NH,loss of a tetra-amide molecule predominates over loss of B.No appreciable isotope and chiral guest configuration effects have been detected in the fragmentation of the homochiral complexes.A distinct configura-tional effect has been appreciated in the CID of the homo-and the heterochiral complexes with all amines used.The results of this study have been discussed in the light of semi-empirical computational evidence.The differences in the CID patterns of the homo-and the heterochiral complexes have been rationalized in terms of structural factors and of the basicity of amine B.