Syntheses of macrocyclic compounds possessing fluorine atoms in their cavities: Structures and complexation with cations

Novel fluorine-containing macrocyclic molecules have been synthesized in or der to clarify the interaction or coordination ability of the C-F unit towa rds metal ions. The cage compounds 1 and 2 were prepared by direct coupling reactions between the appropriate diamines and dibromides, while bond isom ers of the cage compounds were synthesized via fluorinated diaza[3.3]metacy clophanes. Complex formation with alkali metal cations, NH4+, and Ag+ ions has been assessed by picrate extraction experiments. Comparison of the cati on affinities of hosts 1, 2, and 4, shows that the spatial arrangement of t he fluorine atoms strongly affects the donor ability of the host molecules. The hexafluoro cage compound 1, with six fluorine atoms in an ability of t he C-F unit compounds 1 and 2 wt octahedral geometry, exhibits relatively s trong coordination ability towards K+, NH4+, and Ag+ ions, while compound 2 , with four fluorine atoms in a structure similar to that of 1 shows only p oor affinity for these ions. Compound 4, which has six fluorine atoms arran ged in a quasi planar fashion, was found to show weak affinity towards NH4 and Ag+ ions. Thus, octahedrally arranged fluorine atoms evidently provide the best fit for spherical cations. Compound 1 shows characteristic H-1-,C -13-, and F-19-NMR-spectral changes upon complexation. The crystal structur e of 1 has been elucidated and compared to that of the K+ complex. The C-F bonds are found to be slightly elongated in the K+ complex, which is clearl y indicative of coordination of the fluorine atom to K+.